Registration Dossier

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
chromosome aberration assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: liquid
Details on test material:
Name of test material (as cited in study report): o-Acetyltributyl citrate
Substance type: pure active
Physical state: liquid

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
Vehicle(s)/solvent(s) used: polyethylene glycol
Amount of vehicle (if gavage or dermal): 10 mL/kg bw
Purity: PEG 400
Duration of treatment / exposure:
24 and 48 hours after treatment, the bone marrow cells were collected for chromosome aberration analysis
Frequency of treatment:
One single oral treatment
Post exposure period:
24 and 48 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
2000 mg/kg bw
Basis:
nominal conc.
No. of animals per sex per dose:
10 animals (6 male and 6 female rats, 5 of each sex were evaluated)
Control animals:
yes, concurrent vehicle
Positive control(s):
Cyclophosphamide (CPA)
- Justification for choice of positive control(s): CPA is known to induce a distinct increase in induction of aberration frequency
- Route of administration: Once oral by gavage
- Dose: 15 mg/kg bw

Examinations

Tissues and cell types examined:
Bone marrow: at least 100 well spread metaphases per animals were scored for cytogenetic damage
Evaluation criteria:
The test item is classified as mutagenic if it induces either a dose-related increase in the number of structural chromosomal aberrations and a reproducible statistically significant positive response for at least one of the test points.
Statistics:
non-parametric Mann-Whitney test

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Remarks:
The mitotic index was slightly reduced after 24 h
Vehicle controls validity:
valid
Positive controls validity:
valid
Additional information on results:
RESULTS OF RANGE-FINDING STUDY
A single dose was administered at 2000 mg/kg bw to 4 animals (2 males/2 females)
Solubility: Formulated in PEG 400
Clinical signs of toxicity in test animals: Signs recorded 1 - 48 h post-treatment. All animals showed reduction of spontaneous activity at all time points.
Evidence of cytotoxicity in tissue analyzed: The mitotic indices were slightly reduced at 2000 mg/kg bw in the main study indicating that the test item had a slight cytotoxic effect to the bone marrow
Rationale for exposure: 2000 mg/kg bw was the highest dose as required by regulatory Guidelines and expresses the MTD

RESULTS OF DEFINITIVE STUDY
Types of structural aberrations for significant dose levels: No enhancement of the aberrations frequencies
Appropriateness of dose levels and route: The single dose selected of 2000 mg/kg bw was appropriate, as it reflected the MTD and had a slight cytotoxic effect to the bone marrow after 24 h
Statistical evaluation: No significant differences for the test item as compared to the control group

Any other information on results incl. tables

Table: Experimental results

Experimental group

Dose
mg/kg bw

Preparation hours post administra-tion

Number of cells scored

% aberrant cells

Incl. Gaps Excl. gaps

Mean mitotic index (%)

PEG 400

0

24

1000

0.3

0.3

4.87

o-Acetytributyl citrate

2000

24

1000

0.6

0.6

3.52

Cyclophosphamide

15

24

1000

12.1***

11.8***

3.09

o-Acetytributyl citrate

2000

48

1000

0.3

0.3

5.30

 

*** = p<0.0001

 

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
O-Acetyltributyl citrate did not induce chromosomal aberration in the rat in vivo
Executive summary:

A chromosomal aberration study according to OECD 475 was performed in rats in vivo after a single dose of 2000 mg/kg bw O-Acetyltributyl citrate. Five animals per sex and group, i.e. one vehicle control group, two test item groups and one positive control group were employed for the study. The test item was formulated in PEG 400. 24 and 48 h post-treatment, bone marrow cells were collected and 100 well-spread metaphases/animal were scored for chromosomal aberrations. Test item-treated animals showed reduction of spontaneous activity.

The mitotic index was slightly reduced after 24 h, but the test substance did not induce chromosomal aberrations at any time point investigated.

In contrast, the positive control substance induced a highly significant effect documenting the sensitivity of the test system. It can be assumed that the same applies to triethyl citrate (CAS 77-93-0) as it is a near analogue to the test substance acetyl tributyl citrate.