Tributyl citrate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vivo

Description of key information

Based on all pieces of weight of evidence it is clear that tributyl citrate is not mutagenic. Genetic toxicity in vitro: 1) ATEHC was negative with and without metabolic activation in a bacterial reverse mutation assay (Ames test) according to OECD 471 (GLP). [Read-across data from acetyltri-2-ethylhexylcitrate (CAS 144-15-0)] 2) ATCB was negative with and without metabolic activation in a mammalian cell gene mutation assay according to OECD 476 (GLP). [Read-across data from tributyl-O-acetylcitrate (CAS 77-90-7)] Genetic toxicity in vivo: 1) ATBC was tested in a chromosomal aberration study according to OECD 475 and found to be negative [Read across data from tributyl-O-acetylcitrate (CAS 77-90-7)]

Link to relevant study records

Reference

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:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

chromosome aberration assay

Species:

rat

Strain:

Wistar

Sex:

male/female

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

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

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

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

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

 

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 tributyl citrate (CAS 77-94-1) as it is a near analogue to the test substance acetyl tributyl citrate.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vivo:

Genetic toxicity in vitro

There is no study available for this endpoint for the target substance tributyl citrate, therefore data on its structural analogues is taken into account (please refer to the separate read-across statement for further explanation of this procedure):

Acetyltri-2 -ethylhexylcitrate (ATEHC) was tested in the Ames Test for its ability to induce gene mutations in the plate incorporation test (experiment I) and in the preincubation test (experiment II) with Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100 and TA 102 (Hamann, 2000; GLP study according to OECD 471 and EU method B.14). The test item was tested in two independent experiments at several concentrations. Each assay was conducted with and without metabolic activation (S9 mix). The concentrations, including the controls, were tested in triplicate. The following concentrations of the test item were prepared and used in the experiments: 100.0, 316.2, 1000, 2000, 3000 and 4000 µg/plate. Slight toxic effects of the test item (indicated by a reduction of the spontaneous rate) were observed at the highest investigated dose without metabolic activation in the tester strains TA 100 (2nd experiment) and TA 1537 (1st experiment). No substantial increases in the revertant colony numbers of any of the five test strains were detected at any dose level of the test item neither with or without metabolic activation in both independently performed experiments. Therefore, the test item is considered to be non-mutagenic in this bacterial reverse mutation assay. As positive controls reference mutagens were tested in parallel to the test item. They showed a distinct increase of induced revertant colonies. It can be assumed that the same applies to tributyl citrate (CAS 77-94-1) as it is a near analogue to the test substance acetyltri-2 -ethylhexylcitrate (ATEHC).

ATBC did not induce mutations in the Mouse Lymphoma Assay (L5178Y TK +/-) with and without metabolic activation (Bigger and Harbell, 1991; cited in US EPA (2003) HPV Chemicals Challenge Program). The test has been carried out according to OECD Guideline 476.

Taking all these result into account, it can be concluded that tributyl citrate is not mutagenic.

Genetic toxicity in vivo

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 (Bigger and Harbell, 1991). 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.

Justification for selection of genetic toxicity endpoint
GLP and guideline study conducted on mammalian cells with the structural analogue ATBC.

Justification for classification or non-classification

ATBC was tested in a variety of valid in vitro and in vivo test systems and in all of these tests negative results were obtained. Therefore, there is no need for classification. Acetyltri-2 -ethylhexylcitrate (ATEHC, CAS 114-15-0) was negative in an Ames test. As the substance tributyl citrate (CAS 77-94-1) is a near analogue to these substances it can be considered to be also not classified.