Registration Dossier

Administrative data

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:
1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1981
Report Date:
1981

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: HRC Report Number TCO 17 & 18/ 81305
GLP compliance:
yes
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Triphenyl Phosphit
- Physical state: clear colorless liquid

Test animals

Species:
mouse
Strain:
other: COBS CD-I (ICR) BR
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River U.K. Limited, Margate, Kent
- Weight at study initiation: 18 and 21 grams
- Fasting period before study: overnight
- Housing: plastic disposable cage
- Diet: free access to Spratt's Laboratory Diet No. 1
- Water: tap water, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22
- Air changes (per hr): 30
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Vehicle(s)/solvent(s) used: corn oil
Frequency of treatment:
The total dosoges were given as two equal administrations separated by an interval of 24 hours.
Post exposure period:
6h
Doses / concentrationsopen allclose all
Dose / conc.:
1 250 mg/kg bw/day (actual dose received)
Remarks:
total dose divided over two treatments
Dose / conc.:
2 500 mg/kg bw/day (actual dose received)
Remarks:
total dose divided over two treatments
Dose / conc.:
5 000 mg/kg bw/day (actual dose received)
Remarks:
total dose divided over two treatments
No. of animals per sex per dose:
5
Control animals:
yes, concurrent vehicle
Positive control(s):
Mitomycin C, batch number 40F-0404, was used as the positive control compound. It was prepared as a solution in sterile 0.9% saoline at a concentration of 0.4 mg/ml. It was adminitered by IP injection.

Examinations

Tissues and cell types examined:
The femurs were cleared of tissue and one epiphysis removed from each bone. A direct bone marrow smear was made onto a slide containing a drop of calf serum. The slide was cleaned by inversion in methanol for 24 hours and air-dried immediately before use. One smear was mode from each femur.
Details of tissue and slide preparation:
The prepared smears were air-dried and fixed in methanol overnight. After fixation, the smears were air-dried and placed in buffered distilled water (pH 6.8) for 10 minutes prior to staining In Giemsa (dilution Factor I part Giemsa : 9 parts buffered distilled water pH 6.8) for 10 minutes. After rinsing in buffered distilled water (pH 6.8), the slides were air-dried and mounted in OPX. The stained smears were examined by light microscopy to determine the incidence of micronucleated cells per 1000 polychromatic erythrocytes per animal and the ratio of normochromatic to polychromatic erythrocytes.
Evaluation criteria:
A compound was considered to show evidence of mutagenic activity if it produced a statistically significant increase in micronucleated cells compared to the concurrent negative control values.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
RESULTS OF RANGE-FINDING STUDY
- Dose range: Phase I: 500, 5000, 10000, 15000, 24400 mg/kg; Phase II: 6000, 7000 and 8000 mg/kg
After administration of Triphenyl Phosphite at a total dosage of 500 mg/kg bodyweight, no toxic reactions were observed. At total dosages between 5000 and 24400 mg/ltg bodyweight, a toxic reaction consisting of tremors was observed 30 minutes after dosing. The tremors decreased over the next 1.5 hours until they were not observed two hours after each dose. From 10000 mg/kg and higher all animals died. At 6000, 7000 and 8000 mg/kg, 6/10, 6/10 and 9/10 animals died. From the above results, a top dosage of 5000 mg/kg bodyweight was chosen for the micronucleus test which, it was indicated, would cause one or two deaths.

RESULTS OF DEFINITIVE STUDY
In this experiment the negative control group gave a mean count of 0.1 micronucleated cells which was within the range for previous unrelated experiments. After administration of Triphenyl Phosphite at all dosages, the group mean micronucleated cell counts were comparable with the concurrent control value and within the laboratory standard range for negative controls obtained In previous unrelated experiments.

In this experiment the negative control group gave a mean ratio of 1.86 normochromatic to polychromatic cells. After administration of Triphenyl Phosphite at the highest total dosage of 5000 mg/kg bodyweight, the normochromatic to polychromatic cell ratios were comparable with the concurrent control values. The ratios of the two lower dosages were, therefore, not scored. The positive control group administered intraperitoneally with Mitomycin C gave a group mean ratio of 7.32 normochromatic to polychromatic cells.

At total dosages of 1250 and 2500 mg/kg bodyweight no toxic reactions or mortalities were observed. At a total dosage of 5000 mg/kg bodyweight, a toxic reaction consisting of tremors was observed 30 minutes after dosing. The tremors decreased over the next 1.5 hours until they were not observed two hours after each dose. There were 5 mortalities at this dose level. Advanced visceral autolysis prevented any post mortem examination in all animals. After administration of Mitomycin C, no toxic reactions or mortalities were observed.

Any other information on results incl. tables

Summary of results

Number of micronucleated cells per 1000 polychromatic erythrocytes per animal NCE/PCE Ratio
Test group mean range mean range
negative control 0.1 0-1 1.86 1.01-4.96
1250 mg/kg TPP 0.2 0-1 + +
2500 mg/kg TPP 0.2 0-1 + +
5000 mg/kg TPP 0.2 0-1 1.38 1.09-1.86
positive control (8 mg/kg) 27.7 7-67 7.52 3.24-16.37

+ Slides not scores for ratio

Applicant's summary and conclusion