Registration Dossier

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Referenceopen allclose all

Reference Type:
other: cited in OECD SIDS 2003
Title:
Unnamed
Year:
2002
Report Date:
2002
Reference Type:
other: OECD SIDS
Title:
SIDS Initial Assessment Report, N-tert-butylbenzothiazole-2-sulphenamide, CAS No 95-31-8
Author:
OECD
Year:
2003
Bibliographic source:
UNEP Publications

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Deviations:
no
Principles of method if other than guideline:
Groups, each of seven mice, were dosed once via the intraperitoneal route with the test substance at 500, 100 or 2000 mg/kg bw. One group of mice from each dose level was killed by cervical dislocation 24 hours following treatment and a second group dosed with 2000 mg/kg bw was killed after 48 hours.
Immediately following termination (i.e. 24 or 48 hours after dosing), both femurs were dissected from each animal, aspirated with foetal calf serum and bone marrow smears prepared following centrifugation and re-suspension. The smears were air-dried, fixed in absolute methanol and stained. The incidence of micronucleated cells per 2000 polychromatic erythrocytes (PCE-blue stained immature cells) per animal was scored.
GLP compliance:
yes (incl. certificate)
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
N-tert-butylbenzothiazole-2-sulphenamide

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male

Administration / exposure

Route of administration:
intraperitoneal
Duration of treatment / exposure:
24 and 48 h
Frequency of treatment:
once
Doses / concentrations
Remarks:
Doses / Concentrations:
500, 1000, 2000 mg/kg bw
Basis:

No. of animals per sex per dose:
7 males/ dose
Control animals:
yes, concurrent vehicle

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
valid
Negative controls validity:
not specified
Positive controls validity:
valid

Any other information on results incl. tables

Range-finding study:

In animals dosed with test material, at maximum recommended dose level of 2000 mg/kg bw, via the oral and intraperitoneal route no premature deaths were recorded. One animal dosed via the intraperitoneal route demonstrated one clinical sign, diuresis.

The test material showed no marked differences in its toxicity to male or female mice; it was therefore considered from the authors to be acceptable to use males only for the main study. The intraperitoneal route was selected for use in the main study in an attempt to maximize exposure of the animals to the test substance. The maximum recommended dose (MRD) of the test substance, 2000 mg/kg bw, was selected for use in the main study, with 1000 and 500 mg/kg bw as the lower dose levels.

Micronucleus study:

Mortality: none during the study

Clinical signs: Clinical signs were observed in animals dosed with test material at and above 500 mg/kg and included as follows: hunched posture, pilo-erection, lethargy and ptosis. The animals appeared to be more sensitive to the test substance in the main-study than observed in the preliminary range-finding study.

Effect on PCE/NCE ratio: a statistically significant decrease in the PCE/NCE ratio was seen in the 48 -hour 2000 mg/kg and 24 -hour 500 mg/kg test material groups when compared to their concurrent vehicle control groups. The PCE/NCE ratios for the 1000 and 2000 mg/kg 24 -hour test material dose groups were also lower than their concurrent vehicle control. These, accompanied by the observation of clinical signs, were taken to indicate that systemic absorption and adequate exposure of the bone marrow had been achieved.

Genotoxic effects: Negative.

There were no statistically significant increases in the frequency of micronucleated PCEs in any of the test material dose groups when compared to their concurrent vehicle control groups.

The positive control group showed a market increase in the incidence of micronucleated polychromatic erythrocytes hence confirming the sensitivity of the system to the known mutagenic activity of cyclophosphamide under the conditions of the test.

Summary of group mean data

 Treatment group  Number of PCE with micronuclei per 2000 PCE    PCE/NCE ratio  
   Group mean  SD  Group mean  SD
 Vehicle control, 48 h sampling time  2.0 1.2  0.88  0.21 
 Vehicle control, 24 h sampling time  2.6 2.3  0.85  0.26 
Positive control, 24 h sampling time   34.00** 18.3 1.56  0.63 
 2000 mg/kg, 48 h sampling time  1.4 1.3  0.59*  0.25 
 2000 mg/kg, 24 h sampling time  2.4  2.6  0.71  0.38
 1000 mg/kg, 24 h sampling time  2.1  2.3  0.62  0.32
 500 mg/kg, 24 h sampling time  1.6  1.4  0.53*  0.27

* p< 0.05

** p< 0.001

Applicant's summary and conclusion

Conclusions:
Interpretation of results: negative
Executive summary:

Groups, each of seven mice, were dosed once via the intraperitoneal route with the test substance at 500, 100 or 2000 mg/kg bw. One group of mice from each dose level was killed by cervical dislocation 24 hours following treatment and a second group dosed with 2000 mg/kg bw was killed after 48 hours.

Immediately following termination (i.e. 24 or 48 hours after dosing), both femurs were were dissected from each animal, aspirated with foetal calf serum and bone marrow smears prepared following centrifugation and re-suspension. The smears were air-dried, fixed in absolute methanol and stained. The incidence of micronucleated cells per 2000 polychromatic erythrocytes (PCE-blue stained immature cells) per animal was scored.

There were no statistically significant increases in the frequency of micronucleated PCEs in any of the test material dose groups when compared to their concurrent vehicle control groups.