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EC number: 404-370-8 | CAS number: 126990-35-0 DCPMS; DYNASYLAN 9415; EURENOR 5023; SAN-30; WACKER SILAN CP2-DIMETHOXY; Z-6228
Endpoint summary
Administrative data
Key value for chemical safety assessment
Genetic toxicity in vitro
Description of key information
In a reliable and valid gene mutation study in bacteria, conducted according to Japanese guidelines with a protocol similar to the OECD Test Guideline 471 and in compliance with GLP, dicyclopentyl(dimethoxy)silane (CAS 126990-35-0) did not induce mutagenic activity in Salmonella strains (Salmonella typhimurium TA1535, TA1537, TA98, TA100) at up to 313 μg/plate (limited by cytotoxicity) and in Escherichia coli (WP2 uvrA) at up to 5000 μg/plate, with and without S9. The test substance was concluded to be negative for mutagenicity to bacteria under the conditions of the test (BML Incorporation, 1993)
In a reliable in vitro mammalian chromosome aberration study conducted according to OECD Guideline 473 and in compliance with GLP, dicyclopentyl(dimethoxy)silane was not clastogenic to human lymphocytes at concentrations up to 565 μg/ml (limited by cytotoxicity) either in the presence or absence of metabolic activation by S9 (Safepharm Laboratories Limited, 1996)
Link to relevant study records
- Endpoint:
- in vitro gene mutation study in bacteria
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 4 February to 16 March 1992
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals
- Deviations:
- no
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 471 (Bacterial Reverse Mutation Assay)
- Deviations:
- yes
- Remarks:
- (only 2 replicate plates/concentration)
- GLP compliance:
- yes
- Type of assay:
- bacterial reverse mutation assay
- Target gene:
- histidine locus (Salmonella typhimurium strains)
tryptophan locus (Escherichia coli WP2 uvrA) - Species / strain / cell type:
- other: Salmonella typhimurium TA1535, TA1537, TA98, TA100, Escherichia coli WP2 uvrA
- Additional strain / cell type characteristics:
- not applicable
- Metabolic activation:
- with and without
- Metabolic activation system:
- S9 microsomal fraction prepared from phenobarbital- and 5,6-benzoflavone-induced rat liver
- Test concentrations with justification for top dose:
- S. typhimurium strains:
0, 2.4, 4.9, 10, 20, 39 and 78 μg/plate, without S9
0, 2.4, 4.9, 10, 20, 39 and 78 μg/plate, with S9 for TA1535 and TA100
0, 10, 20, 39, 78, 156 and 313 μg/plate, with S9 for TA1537 and TA98
Escherichia coli WP2 uvrA:
0, 313, 625, 1250, 2500 and 5000 μg/plate, with or without S9 - Vehicle / solvent:
- - Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: test material insoluble in water, DMSO is included in the list of recommended solvents - Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- Remarks:
- DMSO
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- furylfuramide
- Remarks:
- 0.01 μg/plate TA100 and WP2 uvrA; 0.1 μg/plate TA98 (without S9)
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- Remarks:
- DMSO
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- sodium azide
- Remarks:
- 0.5 μg/plate TA1535 (without S9)
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- Remarks:
- DMSO
- True negative controls:
- no
- Positive controls:
- no
- Positive control substance:
- other: 2-methoxy-6-chloro-9-[3-(2-chloroethyl)-aminopropylamino]acridine.2HCl (ICR-191) 1 μg/plate TA1537 (without S9)
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- Remarks:
- DMSO
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- benzo(a)pyrene
- Remarks:
- 5 μg/plate TA100, TA98 and TA1537 (with S9)
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- Remarks:
- DMSO
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- other: 2-aminoanthracene: 2 μg/plate TA1535; 5 μg/plate WP2 uvrA (with S9)
- Details on test system and experimental conditions:
- METHOD OF APPLICATION: preincubation
DURATION
- Preincubation period: 20 min
- Exposure duration: 48 h in plates
SELECTION AGENT (mutation assays): depleted levels of histidine or tryptophan in agar medium to select for mutants
NUMBER OF REPLICATIONS: 2 plates/concentration. 2 independent experiments, but in the second only TA1535, TA1537, TA98 and TA100 were tested without S9 and only TA1535 and TA100 were tested with S9.
DETERMINATION OF CYTOTOXICITY
- Method: relative total growth
OTHER:
- Type and composition of metabolic activation system:
- species and cell type: rat, S9 fraction
- quantity: 0.1 ml S9 fraction per 1 ml S9 mix, 0.5 ml S9 mix per plate
- induced or not induced: incuded
- chemicals used for induction: phenobarbital and 5,6-benzoflavone
- co-factors used: Boehringer Mannheim Yamanouchi KK, lot number 712.713; MgCl2 8.0 μmol; KCl 33 μmol; G6P 5 μmol; NADPH 4 μmol; NADH 4 μmol; Na-phosphate buffer (pH 7.4) 100 μmol. - Evaluation criteria:
- Results considered positive if there was a reproducible increase in the mutant frequency of at least twice that of the solvent control at least one time point, or a concentration-related increase over more than one time point.
- Statistics:
- No data
- Species / strain:
- other: S. typhimurium TA1535, TA1537, TA98, TA100, E. coli WP2 uvrA
- Metabolic activation:
- with and without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- 39 μg/plate in TA100, TA1535, TA1537 without S9; 78 μg/plate in TA98 without S9 and TA100, TA1535 with S9; 313 μg/plate in TA98, TA1537 with S9
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not examined
- Positive controls validity:
- valid
- Additional information on results:
- TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: no data
- Effects of osmolality: no data
- Evaporation from medium: no data
- Water solubility: no data
- Precipitation: no data
- Other confounding effects: no data
RANGE-FINDING/SCREENING STUDIES: a range-finding study was conducted with 0, 1.2, 4.9, 20, 78, 313, 1250 and 5000 μg/plate. No growth inhibition was observed with WP2 uvrA. Growth inhibition was noted at 78 μg/plate and above without S9 for all Salmonella strains and with S9 for TA1535 and TA100. Growth inhibition was seen at 313 μg/plate and above with S9 for TA1537 and TA100.
COMPARISON WITH HISTORICAL CONTROL DATA: no data
ADDITIONAL INFORMATION ON CYTOTOXICITY: without S9, cytotoxicity occurred at 78 μg/plate for TA1535, TA98 and TA100 and at 39 μg/plate for TA1537. With S9, cytotoxicity was seen at 78 μg/plate for TA1535 and TA100 and at 156 μg/plate and above for TA1537 and TA98. No toxicity was observed with WP2 uvrA at up to 5000 μg/plate, with or without S9. - Remarks on result:
- other: all strains/cell types tested
- Conclusions:
- In a reliable and valid gene mutation study in bacteria, conducted according to Japanese guidelines with a protocol similar to the OECD Test Guideline 471 and in compliance with GLP, dicyclopentyl(dimethoxy)silane did not induce mutagenic activity in Salmonella strains (Salmonella typhimurium TA1535, TA1537, TA98, TA100) at up to 313 μg/plate (limited by cytotoxicity) and in Escherichia coli (WP2 uvrA) at up to 5000 μg/plate, with and without S9.
- Executive summary:
In a GLP study conducted according to Japanese guidelines, DCPMS was evaluated for its ability to induce mutation in a bacterial reverse mutagenicity (Ames) assay in four strains of Salmonella typhimurium and Escherichia coli WP2 uvrA, with and without a rat metabolic activation fraction (S9).
After a range-finding study, the S. typhimurium strains were exposed in a preincubation assay to the test material at up to 78 μg/plate without S9 (all four strains) and with S9 for TA1535 and TA100; at up to 313 μg/plate for TA1537 and TA98; E.coli WP2 uvrA was tested at up to 5000 μg/plate both with and without S9. The solvent, DMSO, was used as the vehicle control and appropriate known mutagens provided the positive controls. Plates were prepared in duplicate and incubated for 48 hours before counting the revertant colonies. Inhibition of the background lawn was noted as an indication of cytotoxicity. A second independent experiment was conducted, at up to 78 μg/plate using the four Salmonella strains without S9 and TA1535 and TA100 with S9.
No reproducible, concentration-related increase in mutant frequency was observed with any bacterial strain at any concentration of the test material, when compared to the solvent control. The positive controls induced the expected increases in mutant frequencies, confirming the validity of the assay. A thinning of the background lawn at the higher concentrations with the Salmonella strains indicated that the test material was cytotoxic to these strains but not to WP2 uvrA.
Under the conditions of this study, DCPMS showed no mutagenic potential in a bacterial reverse mutagenicity (Ames) assay with four strains of S. typhimurium and E. coli WP2 uvrA
- Endpoint:
- in vitro cytogenicity / chromosome aberration study in mammalian cells
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 30 August 1995 to 25 January 1996
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
- Deviations:
- no
- Qualifier:
- according to guideline
- Guideline:
- EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)
- Version / remarks:
- 92/69/EEC, Method B10
- Deviations:
- no
- GLP compliance:
- yes (incl. QA statement)
- Type of assay:
- in vitro mammalian chromosome aberration test
- Species / strain / cell type:
- lymphocytes: human
- Details on mammalian cell type (if applicable):
- not applicable
- Additional strain / cell type characteristics:
- not applicable
- Metabolic activation:
- with and without
- Metabolic activation system:
- Aroclor 1254-induced S9 from the livers of male Sprague-Dawley rats
- Test concentrations with justification for top dose:
- With metabolic activation: 18, 35.5, 71, 141.3, 282.5, 565, 1130, 2260 µg/ml
Without metabolic activation: 2.25, 4.5, 9.0, 18, 35.5, 53.25, 71, 141.3 µg/ml - Vehicle / solvent:
- - Vehicle(s)/solvent(s) used: acetone
- Justification for choice of solvent/vehicle: well known solvent - Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- Remarks:
- acetone
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- ethylmethanesulphonate
- Remarks:
- in dimethyl sulphoxide. 500 µg/ml. For cultures in the absence of S9
- Untreated negative controls:
- no
- Negative solvent / vehicle controls:
- yes
- Remarks:
- acetone
- True negative controls:
- no
- Positive controls:
- yes
- Positive control substance:
- cyclophosphamide
- Remarks:
- in culture medium without serum. 25 µg/ml. For cultures in presence of S9
- Details on test system and experimental conditions:
- METHOD OF APPLICATION: in medium
DURATION
- Preincubation period: 48 h
- Exposure duration: 4 h (with S9), 20 h (without S9), 44 h (without S9)
- Expression time (cells in growth medium): 16 h, 40 h (both with S9). Cultures in the absence of S9 were treated continuously.
SPINDLE INHIBITOR (cytogenetic assays): demecolcine (Colcemid 0.1 µg/ml)
STAIN (for cytogenetic assays): 5% Gurrs Giemsa R66
NUMBER OF REPLICATIONS: 2
NUMBER OF CELLS EVALUATED: 100 per culture
DETERMINATION OF CYTOTOXICITY
- Method: mitotic index
OTHER EXAMINATIONS:
- Determination of polyploidy: yes
- Determination of endoreplication: yes
OTHER:
- Type and composition of metabolic activation system:
- species and cell type: rat, liver, S9 fraction
- quantity: 1 ml 10% S9 in standard co-factors added to each 9.0 ml culture
- induced or not induced: induced
- chemicals used for induction: Aroclor 1254, 500 mg/kg bw
- co-factors used: standard [no further information] - Evaluation criteria:
- A positive response was recorded for a particular treatment if the percentage of cells with aberrations markedly exceeded that seen in the vehicle control, either with or without a clear concentration-response relationship. For modest increases in aberration frequency, a concentration-response relationship is generally required and appropriate statistical tests may be applied in order to record a positive response.
- Statistics:
- The frequency of cells with aberrations or polyploidy were compared with the results for the vehicle control using Fisher's Exact test or a Chi-squared test.
- Species / strain:
- lymphocytes: human
- Metabolic activation:
- without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- at 71 µg/ml, the mitotic index was 70% of the vehicle control
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not examined
- Positive controls validity:
- valid
- Species / strain:
- lymphocytes: human
- Metabolic activation:
- with
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- at least a 50% growth inhibition was observed at 565 µg/ml
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not examined
- Positive controls validity:
- valid
- Species / strain:
- lymphocytes: human
- Metabolic activation:
- without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- insufficient scorable metaphases at 71 µg/ml and above 71 µg/ml
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not examined
- Positive controls validity:
- valid
- Species / strain:
- lymphocytes: human
- Metabolic activation:
- with
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- not determined
- Remarks:
- confounding results - a plateau of toxicity was observed, followed by decreased toxicity
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not examined
- Positive controls validity:
- valid
- Species / strain:
- lymphocytes: human
- Metabolic activation:
- without
- Genotoxicity:
- negative
- Cytotoxicity / choice of top concentrations:
- cytotoxicity
- Remarks:
- no scorable metaphases observed at 71 µg/ml
- Vehicle controls validity:
- valid
- Untreated negative controls validity:
- not examined
- Positive controls validity:
- valid
- Additional information on results:
- TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: no data
- Effects of osmolality: no data
- Evaporation from medium: no data
- Water solubility: at higher concentrations, the test material (dissolved in acetone) appeared to float on the surface of the media
- Precipitation:
- Other confounding effects: at higher concentrations, the test material appeared to react with the plastic of the tissue culture flask
RANGE-FINDING/SCREENING STUDIES: the results for cultures in the absence of S9 are repeats using lower concentrations of DCPMS due to cytotoxicity showing no scorable metaphases at 71 µg/ml (original concentrations and data are not provided).
COMPARISON WITH HISTORICAL CONTROL DATA: a frequency of 0 to 4% of cells is judged to be acceptable for structural aberrations, including gaps, in lymphocyte control cultures. Excluding gaps, it is acceptable for 0 to 2% of cells to have structural aberrations, and 0 to 1% of cells to exhibit polyploidy. An observable concentration-response relationship is required for modest increases in aberration frequency.
ADDITIONAL INFORMATION ON CYTOTOXICITY: the plateau of toxicity, followed by decreased toxicity, particularly evident in the 20-hour cultures of experiment 2 in the presence of S9, may be explained by the confounding factors noted above. - Remarks on result:
- other: all strains/cell types tested
- Conclusions:
- In a reliable in vitro mammalian chromosome aberration study conducted according to OECD Guideline 473 and in compliance with GLP, dicyclopentyl(dimethoxy)silane was not clastogenic to human lymphocytes at concentrations up to 565 μg/ml (limited by cytotoxicity) either in the presence or absence of metabolic activation by S9.
- Executive summary:
In this GLP study, carried out according to OECD guideline 473 (and EU Method B.10), DCPMS was examined for clastogenic activity in primary cultures of human lymphocytes, both with and without metabolic activation by the microsomal enzyme fraction S9.
In Experiment 1, cell cultures were treated with DCPMS at up to 2260 μg/ml (with S9) for 4 hours, or up to 71 μg/ml (without S9) for 20 hours, and harvested at 20 hours. Cultures were then harvested and fixed for cytotoxicity and metaphase spread evaluation. Experiment 2 was carried out in the same way, with additional cultures harvested at 44 hours. A concentration of 141.3 μg/ml was also included in the absence of metabolic activation. Cultures treated with up to 565 μg/ml (with S9) and 71 μg/ml (without S9) were chosen for metaphase analysis, based on cytotoxicity results.
No significant concentration-related increases in the frequency of cells with chromosome aberrations or an abnormal number of chromosomes were observed.
Referenceopen allclose all
A doubling of revertants was seen in the first experiment at 4.9 μg/plate in TA1535 without S9, but this was not observed in the second experiment and, as no increase in mutant frequency was seen at any other concentration level, it was concluded that this was not related to the test material.
Table 1:Number of revertants per plate (mean of 2 plates) – Experiment 1
Bacterial strain |
TA100 |
TA1535 |
TA98 |
||||||
Concentration of test material, |
- MA |
+ MA |
Cytotoxic |
- MA |
+ MA |
Cytotoxic |
- MA |
+ MA |
Cytotoxic |
0* |
104 107 (106) |
104 130 (117) |
no |
11 11 (11) |
16 16 (16) |
no |
26 23 (25) |
31 33 (32) |
no |
2.4 |
122 137 (130) |
141 123 (132) |
no |
16 13 (15) |
13 18 (16) |
no |
18 23 (20) |
no |
|
4.9 |
100 127 (114) |
139 118 (129) |
no |
22 21 (22) |
16 16 (16) |
no |
22 24 (23) |
no |
|
10 |
135 120 (128) |
106 122 (114) |
no |
19 12 (16) |
22 8 (15) |
no |
22 20 (21) |
37 26 (32) |
no |
20 |
105 105 (105) |
102 100 (101) |
no |
15 8 (11) |
14 18 (16) |
no |
20 20 (20) |
30 29 (30) |
no |
39 |
83 84 (84) |
138 128 (133) |
no |
17 10 (14) |
10 13 (12) |
no |
21 23 (22) |
28 23 (26) |
no |
78 |
89 81 (85) |
93 92 (93) |
yes |
13 10 (12) |
17 17 (17) |
yes |
28 20 (24) |
31 24 (28) |
yes –MA no +MA |
156 |
30 29 (30) |
yes |
|||||||
313 |
35 29 (32) |
yes |
|||||||
Positive control |
AF-2 0.01 µg/plate |
B[a]P 5.0 µg/plate |
NaN3 0.5 µg/plate |
2AA 2.0 µg/plate |
AF-2 0.1 µg/plate |
B[a]P 5.0 µg/plate |
|||
800 762 (781) |
896 985 (941) |
417 355 (386) |
213 208 (211) |
401 422 (412) |
181 204 (193) |
||||
Table 1. (cont’d)
TA1537 |
WP2uvrA |
|||||
- MA |
+ MA |
Cytotoxic |
- MA |
+ MA |
Cytotoxic |
|
0* |
13 18 (16) |
19 24 (22) |
no |
24 22 (23) |
29 37 (33) |
no |
2.4 |
21 25 (23) |
|||||
4.9 |
17 19 (18) |
|||||
10 |
17 25 (21) |
26 20 (23) |
no |
|||
20 |
18 9 (14) |
25 21 (23) |
no |
|||
39 |
8 12 (10) |
27 19 (23) |
yes -MA no +MA |
|||
78 |
10 10 (10) |
22 18 (20) |
yes –MA no +MA |
|||
156 |
15 8 (12) |
yes |
||||
313 |
14 19 (17) |
yes |
16 29 (23) |
38 19 (29) |
no |
|
625 |
17 20 (19) |
31 26 (29) |
no |
|||
1250 |
14 33 (24) |
21 15 (18) |
no |
|||
2500 |
20 24 (22) |
23 37 (30) |
no |
|||
5000 |
27 21 (24) |
25 28 (27) |
no |
|||
Positive control |
ICR-191 1.0 µg/plate |
B[a]P 5.0 µg/plate |
AF-2 0.01 µg/plate |
2AA 10.0 µg/plate |
||
1330 1256 (1293) |
84 104 (94) |
138174(156) | 740692(716) | |||
*solvent control (DMSO)
2AA, 2-aminoanthracene; AF-2, furylfuramide; B[a]P,benzo(a)pyrene; MA, metabolic activation; NaN3, sodium azide
Table 2:Number of revertants per plate (mean of 2 plates) – Experiment 2
Bacterial strain |
TA100 |
TA1535 |
TA98 |
||||||
Concentration of test material, |
- MA |
+ MA |
Cytotoxic |
- MA |
+ MA |
Cytotoxic |
- MA |
+ MA |
Cytotoxic |
0* |
99 137 (118) |
101 120 (111) |
no |
17 9 (13) |
24 19 (22) |
no |
16 21 (19) |
no |
|
2.4 |
103 130 (117) |
107 122 (115) |
no |
12 18 (15) |
21 16 (19) |
no |
28 22 (25) |
no |
|
4.9 |
106 111 (109) |
121 99 (110) |
no |
20 17 (19) |
24 18 (21) |
no |
24 16 (20) |
no |
|
10 |
107 118 (113) |
117 132 (125) |
no |
13 18 (16) |
13 19 (16) |
no |
18 21 (20) |
no |
|
20 |
100 112 (106) |
132 96 (114) |
no |
11 14 (13) |
21 20 (21) |
no |
17 22 (20) |
no |
|
39 |
88 125 (107) |
102 119 (111) |
yes –MA no +MA |
8 13 (11) |
17 20 (19) |
yes –MA no +MA |
17 18 (18) |
no |
|
78 |
75 99 (87) |
99 93 (96) |
yes |
17 9 (13) |
17 9 (13) |
yes |
20 22 (21) |
yes |
|
Positive control |
AF-2 0.01 µg/plate |
B[a]P 5.0 µg/plate |
NaN3 0.5 µg/plate |
2AA 2.0 µg/plate |
AF-2 0.1 µg/plate |
||||
768 784 (776) |
821 819 (820) |
397 395 (396) |
226 214 (220) |
417 412 (415) |
|||||
Table 2. (cont’d)
TA1537 |
|||
- MA |
+ MA |
Cytotoxic |
|
0* |
11 9 (10) |
no |
|
2.4 |
18 16 (17) |
no |
|
4.9 |
13 11 (12) |
no |
|
10 |
9 10 (10) |
no |
|
20 |
8 11 (9) |
no |
|
39 |
8 9 (9) |
yes |
|
78 |
7 4 (6) |
yes |
|
Positive control |
ICR-191 1.0 µg/plate |
||
1208 1110 (1159) |
|||
*solvent control (DMSO)
2AA, 2-aminoanthracene; AF-2,furylfuramide; B[a]P,benzo(a)pyrene; MA, metabolic activation; NaN3, sodium azide
Following the results of cytotoxicity testing, the cultures treated with the following concentrations of DCPMS were selected for metaphase spread analysis (alongside appropriate vehicle and positive controls):
Experiment 1:
Without S9: 35.5, 53.25, 71 µg/ml
With S9: 141.3, 282.5, 565 µg/ml
Experiment 2:
20 h, without S9: 17.8, 35.5, 53.25 µg/ml
20 h, with S9: 141.3, 282.5, 565 µg/ml
44 h, without S9: 53.25 µg/ml
44 h, with S9: 565 µg/ml
Table 1: Results of chromosome analysis – Experiment 1 – 20-hour harvest without metabolic activation
Concentration of test material |
Control* |
Low dose 35.5 µg/ml |
Mid dose 53.25 µg/ml |
High dose 71 µg/ml |
Positive control EMS 500 µg/ml |
|
Cytotoxicity |
no |
no |
no |
no |
yes |
|
Mean (% of control) |
||||||
Mitotic index |
2.50 (100) |
2.43 (97) |
1.88 (75) |
1.43 (57) |
1.20 (48) |
|
Chromosome aberrations |
Total (per 100 cells) |
|||||
Gaps |
6 (3.0) |
3(1.5) |
2 (1.0) |
3 (1.5) |
45 (30.7) |
|
Chromatid aberrations |
breaks |
2 (1.0) |
4 (2.0) |
2 (1.0) |
0 (0.0) |
66 (44.0) |
interchanges |
2 (1.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
15 (10.0) |
|
Isochromatidaberrations |
breaks |
1 (0.5) |
0 (0.0) |
2 (1.0) |
0 (0.0) |
6 (4.0) |
interchanges |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
1 (0.7) |
|
Total number of aberrant cells |
including gaps |
10 (5.0) |
6 (3.0) |
4 (2.0) |
3 (1.5) |
70 (46.7) |
excluding gaps |
5 (2.5) |
3 (1.5) |
3 (1.5) |
0 (0.0) |
54 (36.0) |
|
Mean frequency (%) |
||||||
Polyploidy |
0.0 |
0.5 |
1.0 |
0.0 |
0.0 |
|
* solvent control (acetone)
EMS, ethylmethanesulphonate
Table 2: Results of chromosome analysis – Experiment 1 – 20-hour harvest with metabolic activation
Concentration of test material |
Control* |
Low dose 141.3 µg/ml |
Mid dose 282.5 µg/ml |
High dose 565 µg/ml |
Positive control CP 25 µg/ml |
|
Cytotoxicity |
no |
no |
no |
yes |
yes |
|
Mean (% of control) |
||||||
Mitotic index |
9.23 (100) |
5.00 (54) |
4.93 (53) |
3.08 (33) |
2.00 (22) |
|
Chromosome aberrations |
Total (per 100 cells) |
|||||
Gaps |
0 (0.0) |
0 (0.0) |
1 (0.5) |
0 (0.0) |
21 (10.5) |
|
Chromatid aberrations |
breaks |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
25 (12.5) |
interchanges |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
1 (0.5) |
|
Isochromatidaberrations |
breaks |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
4 (2.0) |
interchanges |
0 (0.0) |
0 (0.0) |
1 (0.5) |
0 (0.0) |
0 (0.0) |
|
Total number of aberrant cells |
including gaps |
0 (0.0) |
0 (0.0) |
2 (1.0) |
0 (0.0) |
39 (19.5) |
excluding gaps |
0 (0.0) |
0 (0.0) |
1 (0.5) |
0 (0.0) |
24 (12.0) |
|
Mean frequency (%) |
||||||
Polyploidy |
0.0 |
0.5 |
0.0 |
0.0 |
0.0 |
|
* solvent control (acetone)
CP, cyclophosphamide
Table 3: Results of chromosome analysis – Experiment 2 – 20-hour harvest without metabolic activation
Concentration of test material |
Control* |
Low dose 17.8 µg/ml |
Mid dose 35.5 µg/ml |
High dose 53.25 µg/ml |
Positive control EMS 500 µg/ml |
|
Cytotoxicity |
no |
no |
no |
yes |
yes |
|
Mean (% of control) |
||||||
Mitotic index |
3.70 (100) |
2.88 (78) |
2.80 (76) |
1.83 (49) |
1.25 (34) |
|
Chromosome aberrations |
Total (per 100 cells) |
|||||
Gaps |
1 (0.5) |
0 (0.0) |
2 (1.0) |
0 (0.0) |
29 (19.3) |
|
Chromatid aberrations |
breaks |
0 (0.0) |
0 (0.0) |
1 (0.5) |
0 (0.0) |
32 (21.3) |
interchanges |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
10 (6.7) |
|
Isochromatidaberrations |
breaks |
3 (1.5) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
3 (2.0) |
interchanges |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
|
Total number of aberrant cells |
including gaps |
3 (1.5) |
0 (0.0) |
3 (1.5) |
0 (0.0) |
53 (35.3) |
excluding gaps |
2 (1.0) |
0 (0.0) |
1 (0.5) |
0 (0.0) |
35 (23.3) |
|
Mean frequency (%) |
||||||
Polyploidy |
0.5 |
0.5 |
0.0 |
0.0 |
0.0 |
|
* solvent control (acetone)
EMS, ethylmethanesulphonate
Table 4: Results of chromosome analysis – Experiment 2 – 20-hour harvest with metabolic activation
Concentration of test material |
Control* |
Low dose 141.3 µg/ml |
Mid dose 282.5 µg/ml |
High dose 565 µg/ml |
Positive control CP 25 µg/ml |
|
Cytotoxicity |
no |
no |
no |
yes |
no |
|
Mean (% of control) |
||||||
Mitotic index |
5.65 (100) |
4.35 (77) |
4.13 (73) |
2.43 (43) |
3.28 (58) |
|
Chromosome aberrations |
Total (per 100 cells) |
|||||
Gaps |
1 (0.5) |
1 (0.5) |
0 (0.0) |
0 (0.0) |
15 (3.8) |
|
Chromatid aberrations |
breaks |
0 (00) |
6 (3.0) |
1 (0.5) |
0 (0.0) |
11 (2.8) |
interchanges |
0 (0.0) |
0 (0.0) |
0 (0.0) |
1 (0.6) |
0 (0.0) |
|
Isochromatidaberrations |
breaks |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
interchanges |
0 (0.0) |
0 (0.0) |
0 (0.0) |
0 (0.0) |
1 (0.3) |
|
Total number of aberrant cells |
including gaps |
1 (0.5) |
7 (3.5) |
1 (0.5) |
1 (0.6) |
25 (6.3) |
excluding gaps |
0 (0.0) |
6 (3.0) |
1 (0.5) |
1 (0.6) |
12 (3.0) |
|
Mean frequency (%) |
||||||
Polyploidy |
0.0 |
0.5 |
0.0 |
0.0 |
0.2 |
|
* solvent control (acetone)
CP, cyclophosphamide
Table 5: Results of chromosome analysis – Experiment 2 – 44-hour harvest without metabolic activation
Concentration of test material |
Control* |
53.25 µg/ml |
|
Cytotoxicity |
no |
no |
|
Mean (% of control) |
|||
Mitotic index |
7.93 (100) |
5.53 (70) |
|
Chromosome aberrations |
Total (per 100 cells) |
||
Gaps |
0 (0.0) |
1 (0.5) |
|
Chromatid aberrations |
breaks |
0 (0.0) |
0 (0.0) |
interchanges |
0 (0.0) |
0 (0.0) |
|
Isochromatidaberrations |
breaks |
4 (2.0) |
0 (0.0) |
interchanges |
0 (0.0)_ |
0 (0.0) |
|
Total number of aberrant cells |
including gaps |
2 (1.0) |
1 (0.5) |
excluding gaps |
2 (1.0) |
0 (0.0) |
|
Mean frequency (%) |
|||
Polyploidy |
0.0 |
0.0 |
|
* solvent control (acetone)
Table 6: Results of chromosome analysis – Experiment 2 – 44-hour harvest with metabolic activation
Concentration of test material |
Control* |
565 µg/ml |
|
Cytotoxicity |
no |
no |
|
Mean (% of control) |
|||
Mitotic index |
8.53 (100) |
8.88 (104) |
|
Chromosome aberrations |
Total (per 100 cells) |
||
Gaps |
0 (0.0) |
3 (1.5) |
|
Chromatid aberrations |
breaks |
0 (0.0) |
1 (0.5) |
interchanges |
0 (0.0) |
0 (0.0) |
|
Isochromatidaberrations |
breaks |
0 (0.0) |
0 (0.0) |
interchanges |
0 (0.0) |
0 (0.0) |
|
Total number of aberrant cells |
including gaps |
0 (0.0) |
4 (2.0) |
excluding gaps |
0 (0.0) |
1 (0.5) |
|
Mean frequency (%) |
|||
Polyploidy |
0.0 |
0.5 |
|
* solvent control (acetone)
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed (negative)
Genetic toxicity in vivo
Description of key information
There are two studies available from a closely related substance, cyclohexyl(dimethoxy)methylsilane (CAS 17865-32-6).
In a mammalian erythrocyte micronucleus test conducted according to OECD Test Guideline 474 and in compliance with GLP, the read-across substance, cyclohexyl(dimethoxy)methylsilane, induced micronuclei in the polychromatic erythrocytes of male mice given 5000 mg/kg bw by oral gavage, a highly toxic dose, but not in females or not in either sex at 2500 mg/kg bw, which was also toxic; the increase is considered to be a result of excessive toxicity (Life Science Research, 1987).
In a rodent dominant lethal assay conducted according to a protocol similar to OECD Test Guideline 478 and in compliance with GLP, there was no evidence of germ cell mutation in mice after oral dosing of cyclohexyl(dimethoxy)methylsilane at up to 1250 mg/kg bw/day, a toxic dose (Life Science Research, 1989).
Link to relevant study records
- Endpoint:
- in vivo mammalian germ cell study: cytogenicity / chromosome aberration
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 9 August 1988 to 30 November 1988
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 478 (Genetic Toxicology: Rodent Dominant Lethal Test)
- Deviations:
- no
- Principles of method if other than guideline:
- A 6-week dominant lethal study in mice
- GLP compliance:
- yes
- Type of assay:
- rodent dominant lethal assay
- Species:
- mouse
- Strain:
- CD-1
- Sex:
- male
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Source: Charles River Breeding Laboratories (UK), Margate, Kent, England
- Age at study initiation: no data
- Weight at study initiation: 24-31 g
- Assigned to test groups randomly: no data
- Fasting period before study: no data
- Housing:group-housed (4 or 5/cage) during acclimation and dosing, high density polypropylene cages with stainless steel tops
- Diet: ad libitum, laboratory animal diet LAD 1
- Water: ad libitum
- Acclimation period: at least 5 days prior to treatment
ENVIRONMENTAL CONDITIONS
- Temperature (°C): target 21, acceptable range 19-25
- Humidity (%): 55+/- 15
- Air changes (per hr): 15/hr
- Photoperiod (hrs dark / hrs light): 12 hr light/12 hr dark
IN-LIFE DATES: From: 19-Aug-1988 To:30-Nov-1988 - Route of administration:
- oral: gavage
- Vehicle:
- - Vehicle(s)/solvent(s) used: corn oil
- Justification for choice of solvent/vehicle: test material freely miscible with corn oil and adequately stable in corn oil over a 72-hr period
- Concentration of test material in vehicle: dosed at 10 ml/kg bw, so presumably 5-125 mg/ml
- Amount of vehicle (if gavage or dermal): 10 ml/kg bw
- Type and concentration of dispersant aid (if powder): not applicable
- Lot/batch no. (if required): no data
- Purity: no data - Details on exposure:
- PREPARATION OF DOSING SOLUTIONS: Required volumes of CHMMS violently mixed with corn oil initially during dose preparation. Inversion of the dose container employed prior to dosing to ensure maintenance of an adequate mixture and to minimise introduction of air bubbles.
DIET PREPARATION
not applicable - Duration of treatment / exposure:
- 6 weeks
- Frequency of treatment:
- Vehicle control and treatment groups treated 5 days/week for 5 weeks and daily for week 6; positive control group treated daily for 3 days during week 6.
- Post exposure period:
- Mating to untreated females (2 females/male) on day following final treatment, then repeated with fresh females seven days later and repeated until 3 separate weekly matings were completed
- Remarks:
- Doses / Concentrations:
50, 250 or 1250 mg/kg bw/day (1250 mg/kg bw/day dose reduced to 750 mg/kg bw/day from Monday of week 3 onwards)
Basis:
actual ingested - No. of animals per sex per dose:
- 25 males
- Control animals:
- yes, concurrent vehicle
- Positive control(s):
- ethylmethanesulphonate
- Justification for choice of positive control(s): guideline recommendation
- Route of administration: oral gavage
- Doses / concentrations: 200 mg/kg bw/day for 3 consecutive days during week 6 - Tissues and cell types examined:
- Treated males were mated with untreated females and the pregnancy rate, pre-implantation loss and post-implantation loss assessed
- Details of tissue and slide preparation:
- CRITERIA FOR DOSE SELECTION: based on a preliminary toxicity test
TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields): On the day following the final treatment, each male mouse was housed for mating with two virgin females. The individual males were re-caged with fresh females seven days later, and this was repeated until 3 separate weekly matings were completed. Females were inspected daily, in the mornings, during the mating period for the presence of vaginal plugs. Sixteen days after introduction to the males, the pregnant females were killed and examined for total implant number and early and late deaths. - Evaluation criteria:
- Comparisons were made between treated and vehicle control groups each week for pregnancy rate, average number of implants (live and dead) and proportions of total implants found dead. Vaginal plugs were recorded to identify mated females and comparisons were made between treated and control groups for the proportion of females found to be pregnant. The average number of implants, live or dead, was calculated for each individual male and for each individual female of the groups, non-pregnant females being excluded, and treated and control groups were compared. Counts of early and late deaths were combined and the proportion of total implants found dead was obtained for each male. Individual male values were then used to test the homogeneity of each group.
- Statistics:
- Proportion of pregnant females: The variation between each treated group and the vehicle control group was assessed by calculation of the term X2B and the significance of the difference between the groups determined from chi-squared distribution tables.
Average number of implants per male and per female: The values for the treated and control groups were compared using a computer-based calculation of the non-parametic Mann-Whitney "U" test.
Proportion of implants found dead per male: A modified chi-squared calculation was performed giving X2W values and subsequent pairwise comparisons of test and control groups were undertaken, with calculation of X2B values. Where X2W values for both groups were non-significant, the significance of any difference between the groups was assessed by consideration of X2B alone. Where one or both groups was not homogeneous, the variance ratio was calculated and the significance obtained from the tables of the variance ratio distribution. - Key result
- Sex:
- male
- Genotoxicity:
- negative
- Toxicity:
- yes
- Remarks:
- Overt signs of toxicity and death in a single male at the top dose level
- Vehicle controls validity:
- valid
- Negative controls validity:
- not examined
- Positive controls validity:
- valid
- Additional information on results:
- RESULTS OF RANGE-FINDING STUDY
- Dose range: 500, 750, 1250 or 2000 mg/kg bw/day
- Clinical signs of toxicity in test animals: A single male in the top dosed group was killed in extremis, showing general lethargy and hind-limb paralysis, after receiving its sixth treatment. At this time and on later days of treatment, the remaining 3 animals of this group showed hyperactivity and/or partial hind-limb paralysis (transient, with full recovery by the morning after each dose). A single male dosed at 1250 mg/kg bw/day, also showed partial hind-limb paralysis on the last day of dosing. No other significant treatment-related effects were observed.
- Rationale for exposure: With the exception of a single male dosed at 2000 mg/kg bw/day, surviving males impregnated both of the two females with which they were caged during the subsequent mating period. Based on these findings and the overt toxicity seen, a maximum dosage of 1250 mg/kg bw/day was selected for the main study.
RESULTS OF DEFINITIVE STUDY
- Appropriateness of dose levels and route: The maximum level of CHMMS administration employed was sufficient to produce overt toxicity, demonstrating that the test material was absorbed.
- Statistical evaluation: There were no statistically significant effects on pregnancy rate, pre-implantation loss or post-implantation loss in any of the CHMMS treated groups. - Conclusions:
- In a well-conducted dominant lethal test, using a protocol similar to OECD guideline 478 and in compliance with GLP, there was no evidence of germ cell mutation in mice after oral dosing of cyclohexyl(dimethoxy)methylsilane at up to 1250 mg/kg bw/day, a toxic dose.
- Executive summary:
A well-conducted dominant lethal test was performed using a protocol similar to OECD guideline 478 and to GLP.
Groups of 25 male mice were given oral gavage doses of 50, 250 or 1250 mg CHMS/kg bw/day, 5 days/week for 5 weeks and 7 days/week during the 6th week. The highest tested dose level was reduced to 750 mg/kg bw/day from the beginning of the 3rd week of dosing following marked adverse reactions to treatment (hyperactivity, ataxia and sedation). A control group received vehicle only (corn oil) and a positive control group received ethylmethanesulphonate at 200 mg/kg bw/day on the last 3 days of week 6.
On the day following the last day of dosing, each male was individually caged with 2 virgin females and allowed to mate; evidence of mating was inspected daily. After 7 days, the females were removed and replaced with fresh virgin females. This process was repeated once more to give a total of 3, 1-week mating periods. Sixteen days after introduction to the males, each group of females was killed and the numbers of live and dead (early or late death) implants were recorded. Three separate parameters were investigated: pregnancy rate, pre-implantation loss and post-implantation loss.
There was no evidence of germ cell mutation in mice after oral dosing with CHMS at up to 1250 mg/kg bw/day, a toxic dose. A clear positive response was seen with the positive control.
- Endpoint:
- in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
- Remarks:
- Type of genotoxicity: chromosome aberration
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 9 April 1987 to 21 August 1987
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- guideline study with acceptable restrictions
- Remarks:
- The study was conducted according to an appropriate OECD test guideline with acceptable restrictions. The restrictions were: only 2 dose levels (guideline recommends 3)
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
- Deviations:
- yes
- Remarks:
- (only 2 dose levels, guideline recommends 3)
- Qualifier:
- according to guideline
- Guideline:
- EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)
- Deviations:
- yes
- Remarks:
- (only 2 dose levels, guideline recommends 3)
- Qualifier:
- according to guideline
- Guideline:
- EPA OTS 798.5395 (In Vivo Mammalian Cytogenics Tests: Erythrocyte Micronucleus Assay)
- Deviations:
- not specified
- GLP compliance:
- yes
- Type of assay:
- micronucleus assay
- Species:
- mouse
- Strain:
- CD-1
- Sex:
- male/female
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Source: Charles River Italia S.p.A., Calco, Italy
- Age at study initiation: 5-6 weeks
- Weight at study initiation: males 28-37 g, females 24-33 g
- Assigned to test groups randomly: yes
- Fasting period before study: overnight
- Housing: 5 animals of one sex/cage, clear polycarbonate cages measuring 35.5 x 23.5 x 19 cm with stainless steel mesh lid and floor
- Diet: ad libitum, Altromin MT diet
- Water: ad libitum
- Acclimation period: at least 5 days
ENVIRONMENTAL CONDITIONS
- Temperature (°C): monitored daily
- Humidity (%): monitored daily
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 hr light/12 hr dark
IN-LIFE DATES: From: 9-Apr-1987 To:21-Aug-1987 - Route of administration:
- oral: gavage
- Vehicle:
- - Vehicle(s)/solvent(s) used: corn oil
- Justification for choice of solvent/vehicle: no data, but well-known vehicle
- Concentration of test material in vehicle: no data, but presumably 250 or 500 mg/ml
- Amount of vehicle (if gavage or dermal): 10 ml/kg bw
- Type and concentration of dispersant aid (if powder): not applicable
- Lot/batch no. (if required): no data
- Purity: no data - Details on exposure:
- PREPARATION OF DOSING SOLUTIONS: Fresh solutions of the test material were prepared for each day's work; solutions being prepared on a weight/volume basis without correction for the displacement due to the volume occupied by the test material.
- Duration of treatment / exposure:
- Single exposure, with harvest times of 24, 48 or 72 hours
- Frequency of treatment:
- Once
- Post exposure period:
- 24, 48 and 72 hours
- Remarks:
- Doses / Concentrations:
2500 or 5000 mg/kg bw
Basis:
actual ingested - No. of animals per sex per dose:
- 5/sex per dose for each exposure period
- Control animals:
- yes, concurrent vehicle
- Positive control(s):
- mitomycin C
- Justification for choice of positive control(s): a well-known clastogen
- Route of administration: oral, gavage
- Doses / concentrations: 5.00 mg/kg bw - Tissues and cell types examined:
- Femoral bone marrow cells obtained by flushing with foetal calf serum
- Details of tissue and slide preparation:
- CRITERIA FOR DOSE SELECTION: Based on a preliminary toxicity test
DETAILS OF SLIDE PREPARATION: Cells were centrifuged at 1000 rpm for 5 min and the supernatant completely removed. A concentrated suspension of the cells of the sediment was then prepared to make smears on slides. The slides were air-dried overnight and then stained with May-Gruenwald and Giemsa, and mounted with Eukitt. Three slides were made for each animal.
METHOD OF ANALYSIS: The slides were randomly coded by a person not involved in the subsequent microscope scoring. They were then examined under medium magnification and one slide from each animal was selected according to staining and quality of smears. Where the toxicity of the test substance was not so great as to inhibit cell proliferation, at least 1000 polychromatic erythrocytes (PCEs) were examined per animal at high magnification (100x) for the presence or absence of micronuclei. At the same time, the number of normochromatic erythrocytes (NCEs) and micronucleated NCEs was also recorded. - Evaluation criteria:
- The ratio of PCEs to NCEs gives an indication of the toxicity of treatment; an increase in the ratio indicates inhibition of cell division. The incidence of micronucleated NCEs gives an indication of the pre-treatment status of the animals. The incidence of micronucleated PCEs provides an index of induced genetic damage. The test material will be considered to have induced micronuclei if a statistically significant and biologically meaningful increase in micronucleus incidence (at p<0.05) is observed in any treatment group, in the pooled data for both sexes, or in the data for male or female groups alone.
- Statistics:
- Only counts from polychromatic cells were subjected to statistical analysis. Using the original observations (and not the micronucleus frequencies per 1000 cells) a modified chi-squared calculation was employed to compare treated and control groups. The degree of heterogeneity within each group was first calculated, and where it was significant it was taken into account in the comparison between groups. If there was no significant within-group heterogeneity, the chi-squared test was used to compare treated groups with the controls. If there was significant within-groups heterogeneity, then that group was compared with the controls using a variance ratio (F) value calculated from the between-group and within-group chi-squared values.
- Sex:
- male
- Genotoxicity:
- positive
- Remarks:
- 5000 mg/kg bw
- Toxicity:
- yes
- Remarks:
- See "any other information" section below
- Vehicle controls validity:
- valid
- Negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Sex:
- female
- Genotoxicity:
- negative
- Toxicity:
- yes
- Remarks:
- See "any other information" section below
- Vehicle controls validity:
- valid
- Negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Sex:
- male/female
- Genotoxicity:
- negative
- Toxicity:
- yes
- Remarks:
- See "any other information" section below
- Vehicle controls validity:
- valid
- Negative controls validity:
- not applicable
- Positive controls validity:
- valid
- Additional information on results:
- RESULTS OF RANGE-FINDING STUDY
- Dose range: 5000 mg/kg bw
- Solubility: no data
- Clinical signs of toxicity in test animals: There was no excessive lethality
- Evidence of cytotoxicity in tissue analyzed: not applicable
- Rationale for exposure: There was no excessive lethality in the preliminary study.
- Harvest times: not applicable
- High dose with and without activation: not applicable
- Other: no data
RESULTS OF DEFINITIVE STUDY
There was no marked increase in the number of micronucleated PCEs in any of the treatment groups at the 24- and 72-hour sampling times. At the 48-hour sampling time, a pronounced increase was observed at the high-dose level. A dose-related increase in the ratio of mature to polychromatic erythrocytes (NCE:PCE ratio) was seen at the 4- hour sampling time in the test material treatment groups. Similar increases were also seen at 24 hours, indicating that the test material exerted an inhibitory effect on the cell division of bone marrow erythropoietic cells.
When analysed by treatment group and the male and female data were combined, no statistically significant increases in the incidence of micronucleated PCEs were observed when compared with the vehicle control group at the 24-, 48- or 72-hour sampling times. When analysed by sex, no statistically significant increases in the incidences of micronucleated PCEs were seen for the female animals when compared with the vehicle controls at any of the sampling times. In the males, a single statistically significant increase was observed at the high-dose level, at the 48-hour sampling time (p<0.01), with increased micronucleus incidence being present in 3 of the 5 animals. This observed micronucleated PCE incidence lay outside the historical negative control values for the laboratory. - Conclusions:
- In a mammlian erythrocyte micronucleus test conducted according to OECD Test Guideline 474 and in compliance with GLP, cyclohexyl(dimethoxy)methylsilane induced micronuclei in the polychromatic erythrocytes of male mice given 5000 mg/kg bw by oral gavage, a toxic dose, but not in females or when the two groups were combined.
- Executive summary:
In a reliable study, conducted to OECD guideline 474 and to GLP, five male and five female mice were treated with a single oral, gavage, dose of CHMS at 2500 or 5000 mg/kg bw. Negative control animals received the vehicle only (corn oil) and positive control animals were treated with mitomycin C. Animals were sacrificed 24, 48 or 72 hours after treatment and bone marrow smear slides were prepared, stained and assessed for micronucleus induction in the polychromatic erythrocytes. The results obtained at each sampling time were subjected to statistical analysis using a modified chi-squared test.
A dose-related increase in the ratio of mature to polychromatic erythrocytes was observed at the 48-hour sampling time in the treatment groups, indicating that the test material exerted an inhibitory effect on the cell division of bone marrow erythropoietic cells. Similar increases were observed at the 24 -hour sampling time. There were no statistically significant increases in the incidences of micronucleated PCEs at any dose-level or sampling time when the results for the male and female animals were combined or those of the females were considered separately and compared with the vehicle control values. For the male animals, a single statistically significant increase was observed at 5000 mg/kg bw at the 48 -hour sampling time, with increases in the micronucleus incidence being seen in three of the five animals and the observed micronucleated PCE incidence lying outside the historical negative control values for the laboratory.
Referenceopen allclose all
During week 2 of dosing, males given 1250 mg/kg bw/day showed transient ataxia, loss of gripping reflex and other behavioural abnormalities. The effects included a brief period of hyperactivity post-dose, followed by ataxia and, in some cases, apparent deep sedation. Recovery was complete within 3 -4.5 hours of dosing. A single male of this group was found dead at the end of week 2. After reducing the dose to 750 mg/kg bw/day, some animals showed post-dose hyperactivity during weeks 3 and 4, and ataxia and prominent testes were also observed. No obvious signs of adverse reactions were seen at the mid- and low-dose levels.
Table: Summary of group data
Treatment group |
Mating week |
Pregnant females |
Total implants |
Dead implants |
Mutagenic indexb |
|||
No. |
%a |
No. |
Mean/female |
No. |
Mean/female |
|
||
Vehicle controls (corn oil) |
1 2 3 |
48 46 46 |
96 92 92 |
559 577 568 |
11.6 12.5 12.3 |
32 24 26 |
0.7 0.5 0.5 |
5.7 4.2 4.6 |
CHMMS, 50 mg/kg bw/day |
1 2 3 |
42 47 48 |
91 94 96 |
529 573 566 |
12.6 12.2 11.8 |
29 30 41 |
0.7 0.6 0.9 |
5.5 5.2 7.2 |
CHMMS, 250 mg/kg bw/day |
1 2 3 |
43 46 46 |
86 92 92 |
524 555 546 |
12.2 12.1 11.9 |
23 30 26 |
0.5 0.7 0.6 |
4.4 5.4 4.8 |
CHMMS, 1250-750 mg/kg bw/day |
1 2 3
|
39 44 39 |
89 92 81 |
461 555 456 |
11.8 12.6 11.7 |
29 18 25 |
0.7 0.4 0.6 |
6.3 3.2 5.5 |
EMS, 200 mg/kg bw/day |
1 2 3 |
43 26 43 |
86 52** 86 |
398 246 507 |
9.3 9.5* 11.8 |
200 100 41 |
4.7 3.8 1.0 |
50.3** 40.7** 8.1* |
a - Percentage of all females caged with surviving, treated males and later confirmed as pregnant.
b - Mutagenic Index = (Total dead implants/total implants) x 100
* - Significantly different from Group 1 value, p<0.05 (based on "per male" analysis)
** - Significantly different from Group 1 value, p<0.001
A range of toxic signs was observed including loss of consciousness, hyperactivity and hypoactivity, loss of equilibrium and unusual gait, fibrillations and tremors, blanching, piloerection and ungroomed appearance. At the high-dose level, seven of the 30 animals died following treatment and were substituted by reserve animals.
Table 1: Summary of Incidence of Micronucleated Cells
Sampling time: 48 hours
MALES |
|||||||||||
|
Incidence of Micronuclei per 1000 cells |
||||||||||
Dose-level |
Scored Cells |
NCE/PCE |
Polychromatic |
Normochromatic |
|||||||
mg/kg |
PCE |
NCE |
Ratio |
Mean |
SE |
Min |
Max |
Mean |
SE |
Min |
Max |
0.00 |
5000 |
5609 |
1.12 |
1.6 |
0.6 |
0.0 |
3.0 |
1.1 |
0.6 |
0.0 |
2.8 |
2500 |
4013 |
4450 |
1.11 |
1.5 |
0.6 |
0.0 |
3.0 |
1.1 |
0.7 |
0.0 |
2.5 |
5000 |
3600 |
5387 |
2.02 |
5.6 |
2.2 |
0.0 |
11.0 |
1.9 |
0.7 |
0.9 |
4.5 |
Mitomycin C |
|||||||||||
5.00 |
1610 |
3632 |
2.84 |
16.1 |
1.3 |
13.5 |
18.0 |
2.5 |
1.0 |
0.6 |
4.0 |
|
|
|
|
|
|
|
|
|
|
|
|
FEMALES |
|||||||||||
|
Incidence of Micronuclei per 1000 cells |
||||||||||
Dose-level |
Scored Cells |
NCE/PCE |
Polychromatic |
Normochromatic |
|||||||
mg/kg |
PCE |
NCE |
Ratio |
Mean |
SE |
Min |
Max |
Mean |
SE |
Min |
Max |
0.00 |
5062 |
3467 |
0.69 |
1.4 |
0.7 |
0.0 |
3.0 |
0.8 |
0.5 |
0.0 |
2.3 |
2500 |
4426 |
7110 |
1.69 |
2.3 |
0.8 |
0.0 |
5.0 |
0.9 |
0.2 |
0.0 |
1.3 |
5000 |
3770 |
7206 |
2.20 |
1.8 |
1.0 |
0.0 |
5.0 |
0.4 |
0.2 |
0.0 |
1.0 |
Mitomycin C |
|||||||||||
5.00 |
3080 |
5219 |
2.12 |
11.3 |
3.5 |
4.0 |
23.3 |
5.1 |
1.7 |
1.1 |
10.0 |
|
|
|
|
|
|
|
|
|
|
|
|
BOTH SEXES |
|||||||||||
|
Incidence of Micronuclei per 1000 cells |
||||||||||
Dose-level |
Scored Cells |
NCE/PCE |
Polychromatic |
Normochromatic |
|||||||
mg/kg |
PCE |
NCE |
Ratio |
Mean |
SE |
Min |
Max |
Mean |
SE |
Min |
Max |
0.00 / |
|
|
|
|
|
|
|
|
|
|
|
0.00 |
10062 |
9076 |
0.9 |
1.5 |
0.4 |
0.0 |
3.0 |
0.9 |
0.4 |
0.0 |
2.8 |
2500 / |
|
|
|
|
|
|
|
|
|
|
|
2500 |
8439 |
11560 |
1.43 |
1.9 |
0.5 |
0.0 |
5.0 |
1.0 |
0.3 |
0.0 |
2.5 |
5000 / |
|
|
|
|
|
|
|
|
|
|
|
5000 |
7370 |
12593 |
2.11 |
3.7 |
1.3 |
0.0 |
11.0 |
1.1 |
0.4 |
0.0 |
4.5 |
Mitomycin C |
|||||||||||
5.00 |
4690 |
8851 |
2.39 |
13.1 |
2.3 |
4.0 |
23.3 |
4.2 |
1.2 |
0.6 |
10.0 |
MEAN = group mean incidence of micronucleated PCEs/NCEs
SE = standard error of the mean incidence
MIN = Minimum value observed in an individual animal
MAX = maximum value observed in an individual animal
Table 2: Statistical analysis
Sampling time: 48 hours
STATISTICAL ANALYSIS – BOTH SEXES |
||||||||
Dose level mg/kg |
Within animals of one group |
Between each group and control group |
||||||
Males |
Females |
X2 |
Sign. |
X2 |
Sign. |
F |
Sign. |
|
0.00 |
0.00 |
10.82 |
N.S. |
|
|
|
|
|
2500 |
2500 |
10.05 |
N.S. |
0.45 |
N.S. |
|
|
|
5000 |
5000 |
25.25 |
** |
|
|
4.17 |
N.S. |
|
Mitomycin C |
5 mg/kg |
17.61 |
* |
|
|
|
37.75*** |
|
|
|
|
|
|
|
|
|
|
MALES ONLY |
||||||||
0.00 |
0.00 |
4.51 |
N.S. |
|
|
|
|
|
2500 |
2500 |
3.37 |
N.S. |
0.02 |
N.S. |
|
|
|
5000 |
5000 |
9.23 |
N.S. |
10.09 |
** |
|
|
|
Mitomycin C |
5 mg/kg |
|
N.C. |
|
N.C. |
|
N.C. |
|
|
|
|
|
|
|
|
|
|
FEMALES ONLY |
||||||||
0.00 |
0.00 |
6.37 |
N.S. |
|
|
|
|
|
2500 |
2500 |
5.66 |
N.S. |
1.01 |
N.S. |
|
|
|
5000 |
5000 |
8.63 |
N.S. |
0.31 |
N.S. |
|
|
|
Mitomycin C |
5 mg/kg |
14.09 |
** |
|
|
9.24 |
* |
|
|
|
|
|
|
|
|
|
|
DIFFERENCES BETWEEN SEXES |
||||||||
|
|
|
|
Between male and female groups |
||||
0.00 |
0.00 |
|
|
0.08 |
N.S. |
|
|
|
2500 |
2500 |
|
|
0.65 |
N.S. |
|
|
|
5000 |
5000 |
|
|
6.90 |
** |
|
|
|
Mitomycin C |
5 mg/kg |
|
|
|
|
2.73 |
N.S. |
|
The chi-squared statistic (X2) and significance level (Sign.) are presented for within-group heterogeneity.
The Chi-squared (X2) or F-statistic (F), and significance level (Sign.) are shown for the comparison between the control and treatment group (or between males and females in the same treatment groups, as appropriate)
N.C. = not calculated
N.S. = not significant
* = statistically significant at p<0.05
** = statistically significant at p<0.01
*** = statistically significant at p<0.001
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed (negative)
Additional information
Information on dicyclopentyl(dimethoxy)silane (CAS 126990-35-0) is available from four reliable bacterial mutagenicity tests. The key study was conducted according to Japanese guidelines and in compliance with GLP. Dicyclopentyl(dimethoxy)silane showed no mutagenic potential in this reverse mutagenicity (Ames) assay in at up to 5000 μg/plate, with or without metabolic activation (BML Inc., 1993a). The three supporting studies were conducted according to OECD Test Guideline 471 and in compliance with GLP. Dicyclopentyl(dimethoxy)silane showed no mutagenic potential with or without metabolic activation in these bacterial mutagenicity assays in S. typhimurium strains TA98, TA100, TA1535, TA1537 and TA1538 at up to 5000 μg/plate (Cytotest Cell Research Gmbh 1995b; Safepharm Laboratories Limited, 1995; Huls AG, 1995). Reliable data are also available on the hydrolysis product of the registered substance, dicyclopentylsilanediol (DCPMS-OH2, CAS 211495-85-1). In a GLP study conducted according to Japanese guidelines, dicyclopentylsilanediol showed no mutagenic potential in an Ames assay in Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537 and Escherichia coli WP2 uvrA at up to 1250 μg/plate, with and without metabolic activation (BML Inc., 1993b).
Further information is available from three reliable in vitro cytogenicity tests, all conducted according to OECD Test Guideline 473 and in compliance with GLP. In the key study dicyclopentyl(dimethoxy)silane
was not clastogenic to human lymphocytes in vitro at concentrations up to 565 μg/ml (limited by cytotoxicity) either in the presence or absence of metabolic activation (Safepharm Laboratories Limited, 1996). In the supporting studies, no clastogenicity was seen in Chinese hamster ovary cells at up to 200 µg/ml (Cytotest Cell Research GmbH, 1995a) or in Chinese hamster V79 cells at up to 120 µg/ml (Huntingdon Research Centre Ltd., 1995) either in the presence or absence of metabolic activation (in both studies, the highest concentration tested was limited by cytotoxicity). In a reliable study, conducted according to a protocol similar to OECD Test Guideline 473, the hydrolysis product was not clastogenic to Chinese hamster lung fibroblast cells at concentrations of up to 1.3 mg/ml (limited by cytotoxicity), either in the presence or in the absence of metabolic activation (BML Inc, 1992).
Two in vivo genotoxicity studies are available for a related substance, cyclohexyl(dimethoxy)methylsilane (CAS 17865-32-6). In a well-conducted dominant lethal test, using a protocol similar to OECD Test Guideline 478 and in compliance with GLP, there was no evidence of germ cell mutation in mice after oral dosing of cyclohexyl(dimethoxy)methylsilane for 2 weeks at up to 1250 mg/kg bw/day, a toxic dose (Life Science Research, 1989).
In a reliable study, conducted according to OECD Test Guideline 474 and in compliance with GLP, cyclohexyl(dimethoxy)methylsilane induced micronuclei in the polychromatic erythrocytes of male mice given 5000 mg/kg bw by oral gavage, a dose that was lethal to some of the animals. No statistically significant effect was seen in females, or when data for males and females were combined, and there was no increase in the frequency of micronuclei in either sex at 2500 mg/kg bw, a toxic dose (Life Science Research, 1987). The occurrence of a positive genotoxic response only at a dose high enough to induce severe toxicity is of questionable relevance to humans and OECD Test Guideline 474 requires testing only up to "the dose producing signs of toxicity such that higher dose levels would be expected to produce lethality." Read-across to the registered substance is considered appropriate as the silicon containing products of hydrolysis have similar functional groups (cyclopentyl/cyclohexyl and methyl), and do not include structural alerts for genotoxicity. The alkoxysilanes, excluding those with functional groups that are known to be associated with genetic toxicity (such as epoxy) are largely non-genotoxic.
The most reliable studies were chosen as key. Where there was more than one reliable study, the most recent was selected. The results of all the studies are in agreement. In view of the availability of in vivo data for the related substance, cyclohexyl(dimethoxy)methylsilane (CAS 17865-32-6) from studies in somatic cells and in germ cells, and the overall weight of evidence of the information available, it is considered that testing for mutagenicity to mammalian cells in vitro is not required, as the overall conclusion for genetic toxicity in the studies was negative.
Justification for classification or non-classification
Based on the available in vitro studies with dicyclopentyl(dimethoxy)silane and in vivo genotoxicity data for the analogue substance cyclohexyl(dimethoxy)methylsilane, dicyclopentyl(dimethoxy)silane does not require classification for mutagenicity according to Regulation (EC) No 1272/2008.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
