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:
07/26/1994 - 10/12/1994
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented study report equivalent or similar to OECD 474

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1995
Report Date:
1995

Materials and methods

Test guidelineopen allclose all
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Qualifier:
equivalent or similar to
Guideline:
EPA OTS 798.5395 (In Vivo Mammalian Cytogenics Tests: Erythrocyte Micronucleus Assay)
GLP compliance:
yes
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Isodecyl Benzoate
- Physical state: clear pale yellow liquid
- Analytical purity: 98%
- Lot/batch No.: C5-8
- Expiration date of the lot/batch: 15 May 1996
- Storage condition of test material: Room temperature

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River U.K. Limited, Margate, Kent, England
- Age at study initiation: approximately 35 days old on despatch
- Assigned to test groups randomly: yes
- Housing: each group was kept, with the sexes separated, in plastic disposable cages
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 4 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 - 25 °C
- Humidity (%): 50 - 64 %
- Air changes (per hr): 20 per hour
- Photoperiod (hrs dark / hrs light): 12 hours light/dark


Administration / exposure

Route of administration:
intraperitoneal
Vehicle:
- Vehicle(s)/solvent(s) used: 1% Methylcellulose
- Lot/batch no. (if required): T32398
Duration of treatment / exposure:
All animals in all groups were dosed with the standard volume of 20 mL/kg bodyweight or 1280 mg/kg bodyweight. Test substance and negative control were dosed by intraperitoneal injection. Mitomycin C, the positive control, was dosed orally by intragastric gavage at 12 mg/kg bodyweight. The animals in the the postive control group were deprived of diet overnight prior to and two hours after dosing.
Frequency of treatment:
Single acute intraperitoneal administration of test substance
Post exposure period:
72 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
1280 mg/kg
Basis:
other: bodyweight
No. of animals per sex per dose:
15 animals per sex (male/female) 30 animals total per dose (Vehicle/Isodecyl Benzoate)
5 animals per sex (male/female) 10 animals total per dose (Mitomycin C)
Control animals:
yes, concurrent vehicle
Positive control(s):
mitomycin C;
- Route of administration: orally, intragastric gavage
- Doses / concentrations: 12 mg/kg bodyweight

Examinations

Tissues and cell types examined:
Bone marrow smears were obtained from test substance and negative control groups at 24, 48 and 72 hours after dosing. Bone marrow smears were obtained form the positive control group at 24 hours after dosing.
Evaluation criteria:
Smears from each animal were examined for the presence of micronuclei in 1000 polychromatic erythrocytes. The ratio of polychromatic to normochromatic erythrocytes was assessed by examination of at least 1000 erythrocytes from each animal.
A positive response is normally indicated by a substantial, statistically significant increase (P < 0.01) in the incidence of micronucleated polychromatic erythrocytes compared to the incidence for the concurrent vehicle control group for at least one of the sampling times: individual and/or group mean values should exceed the laboratory historical control range. A negative result is indicated where individual and group mean incidences of micronucleated polychromatic erythrocytes for animals treated with the test substance are not significantly greater (P>0.01) than incidences for the concurrent control group and where these values fall within the historical control range. An equivocal response is obtained when the resutls cannot be adequately classified using the criteria for a positive or negative response.
Bone marrow cell toxicity (or depression) is normally indicated by a substantial, statistically significant decrease (P<0.01) in the ratio of polychromatic to normochromatic erythrocytes. This decrease would normally be evident at the 48 and 72 hour sampling points, a decrease a tthe 24 hour time point is not necessarily expected because of the relatively long transition time of erythroid cells. A very large decrease in this ratio would be indicaive of a cytostatic or cytotoxic effect.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
valid
Positive controls validity:
valid

Applicant's summary and conclusion

Conclusions:
Isodecyl benzoate did not cause any substantial increase in the incidence of micronucleated polychromatic erythrocytes, Isodecyl benzoate did not show any evidence of causing chromosome damage when administered intraperitoneal in this in vitro test. Bone marrow cell toxicity/depression is indicated by the statistically significant decrease in the ratio of polychromatic to normochromatic erythrocytes obtained for animals treated with Isodecyl benzoate.
Executive summary:

Isodecyl benzoate, when adminsitered by intraperitoneal injection at 1280 mg/kg bodyweight, did not cause a substantial increase in the incidence of micronucleated polychromatic erythroytes. Isodecyl benzoate did not show evidence of causing chromosome damage in this in vivo test. Isodecyl benzoate produced bone marrow cell toxicity/depression as indicated by a statistically significant decrease in the ratio of polychromatic to normochromatic erythrocytes obtained for treated animals.