Octanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1)

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

As octanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1) is expected to readily dissociate into Triethanolamine and Octanoic acid, it is considered appropriate to read across from Octanoic Acid and Triethanolamine. Octanoic acid data is from a peer reviewed scientific journal.

Data source

Reference

Reference Type:

publication

Title:

Salmonella Mutagenicity Tests. IV. Results from the Testing of 300 Chemicals

Author:

Zeiger E, Anderson B, Haworth S, Lawlor T, Mortelmans K.

Year:

1988

Bibliographic source:

Environ Molec Mutagen 11(12):1-158

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

yes

Remarks:

strain with AT base pair as primary reversion site missing

Principles of method if other than guideline:

Test protocol is decribed by Haworth et al., 1983. No strains with AT base pair at the primary reversion site were tested.

[Haworth S, Lawlor T, Mortelmans K, Speck W, Zeiger E (1983): Salmonella mutagenicity results for 250 chemicals. Environ Mutagen 5(Suppl 1):3-142.]

GLP compliance:

not specified

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Octanoic acid

EC Number:

204-677-5

EC Name:

Octanoic acid

Cas Number:

124-07-2

Molecular formula:

C8H16O2

IUPAC Name:

octanoic acid

Test material form:

liquid

Specific details on test material used for the study:

Publication states chemical source as Aldrich Chemical, with a label purity of 99.5% and an analyzed purity of >99%.

Method

Species / strain

Species / strain 1

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain 2

Species / strain / cell type:

S. typhimurium TA 97

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254-induced rat and hamster metabolic activation

Test concentrations with justification for top dose:

0, 10, 33, 100, 333, 1000, 3333 µg/plate
All chemicals were tested initially in a toxicity assay to determine the appropriate dose range for the mutagenicity assay. The toxicity assay was performed using TA100 or the system developed by Waleh et al. [1982]. Toxic concentrations were those that produced a decrease in the number of his+ colonies, or a clearing in the density of the background lawn, or both.

Vehicle / solvent:

DMSO

Controls

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

sodium azide

other: 4-nitro-o-phenylenediamine; 2-aminoanthracene

Details on test system and experimental conditions:

Bacterial Strains
Salmonella typhimunum strains TA97, TA98, TA100, TA1535, and TA1537 were obtained from Dr. Bruce Ames (University of California, Berkeley) and were stored as recommended [Maron and Ames, 1983]. Cultures were grown overnight with shaking at 37°C in Oxoid No. 2 broth, and their phenotypes were analyzed prior to their use for mutagenicity assays.

Preparation of S-9 Fraction
The S-9 (9,000g supernatant) fractions of Aroclor 1254-induced, male Sprague- Dawley rat and male Syrian hamster livers were prepared as described previously [Haworth et al, 1983]. The S-9 mixes were prepared immediately prior to use and contained either 10% or 30% S-9; occasionally, other levels were used. The specific levels used are indicated in Appendix 2. All chemicals were tested in the absence of metabolic activation and with rat and hamster S-9 fractions.

Preincubation Assay
The preincubation assay was performed as described previously [Haworth et al., 1983], with some differences, as described below. The test chemical (0.05 ml), Salmonella culture (0.10 ml), and S-9 mix or buffer (0.50 ml) were incubated at 37°C, without shaking, for 20 min. Chemicals known or suspected to be volatile were incubated in capped tubes. The top agar was added and the contents of the tubes were mixed and poured onto the surface of petri dishes containing Vogel-Bonner medium [Vogel and Bonner, 1956]. The histidine-independent (his') colonies arising on these plates were counted following two days incubation at 37°C. Plates were machine counted (New Brunswick, Edison, NJ; Artek, Farmingdale, NY) unless precipitate was present which interfered with the count, or the colour of the test chemical on the plate reduced the contrast between the colonies and the background agar. At the discretion of the investigators, plates with low numbers of colonies were counted by hand.
Variations in the protocol among the tested chemicals reflect the evolution of the protocol originally described by Haworth et al. [1983]. Four protocol variations are evident from the data in Appendix 2. 1) Testing in strains TA97, TA98, TA100, and TA1535, with some additional testing in strain TA1537; 10% S-9 was used. 2) The first test of a chemical was without activation and with 10% S-9 in the S-9 mix. If a positive result was obtained the test was repeated. If the tests were negative they were repeated without S-9 and with 30% S-9. 3) The order of use of 10% and 30% S-9 was reversed. 4) Initial testing was in strains TA98 and TA100 without activation and with 30% rat and hamster S-9s. If a positive result was obtained in one of these two strains it was repeated and the other strains were not used. If the tests were negative, the other strains were used with 30% and 10% S-9. A chemical was not designated nonmutagenic unless it had been tested in strains TA98, TA100, TA1535, and TA97 and/or TA1537, without activation and with 10% and 30% rat and hamster S9. Occasionally, 5% S-9 was also used in all protocol variations. All chemicals were tested initially in a toxicity assay to determine the appropriate dose range for the mutagenicity assay. The toxicity assay was performed using TA100 or the sytem developed by Waleh et al. [1982]. Toxic concentrations were those that produced a decrease in the number of his+ colonies, or a clearing in the density of the background lawn, or both.
Each chemical was tested initially at half-log dose intervals up to a dose that elicited toxicity, or to a dose immediately below one which was toxic in the preliminary toxicity test. Subsequent trials occasionally used narrower dose increments and may not have included doses in the toxic range. Chemicals that were not toxic were tested, with few exceptions, to a maximum dose of 10 mg/plate.
Chemicals that were poorly soluble were tested up to doses defined by their solubilities. At least five doses of each chemical were tested in triplicate. Experiments were repeated at least one week following the initial trial. A maximum of 0.05 ml solvent was added to each plate. Concurrent solvent and positive controls were run with each trial. The positive controls in the absence of metabolic activation were sodium azide (TA1535 andTA100), 9-aminoacridine (TA97 and TA 1537), and 4-nitro-o-phenylenediamine (TA98). The positive control for metabolic activation with all strains was 2-aminoanthracene.

Evaluation criteria:

The data were evaluated as described previously [Zeiger et al., 1987]. Evaluations were made at both the individual trial and overall chemical levels. Individual trials were judged mutagenic (+), weakly mutagenic (+ W), questionable (?), or non-mutagenic (-), depending on the magnitude of the increase of his+ revertants, and the shape of the dose-response. A trial was considered questionable (?) if the dose-response was judged insufficiently high to support a call of “ +W,” if only a single dose was elevated over the control, or if the increase seen was not dose related. The distinctions between a questionable mutagenic response and a non-mutagenic or weak mutagenic response and between a weak mutagenic response and mutagenic response are highly subjective. It was not necessary for a response to reach two-fold over background for a chemical to be judged mutagenic. A chemical was judged mutagenic (+) or weakly mutagenic (+ W) if it produced a reproducible dose-related response over the solvent control in replicate trials. A chemical was judged questionable (?) if the results of individual trials were not reproducible, if increases in his+ revertants did not meet the criteria for a “+W” response, or if only single doses produced increases in his+ revertants in repeat trials. Chemicals were judged non-mutagenic (-) if they did not meet the criteria for a mutagenic or questionable response. The chemicals were decoded by the chemical repository only after a determination had been made regarding their mutagenicity or non-mutagenicity.

Results and discussion

Test results

Test results 1

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 2

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 3

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 4

Species / strain:

S. typhimurium TA 97

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Test results 5

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Positive controls validity:

valid

Applicant's summary and conclusion

Conclusions:

In this publication, Octanoic acid (CAS 124-07-2) is reported to be non-mutagenic, with and without metabolic activation, in Salmonella typhimurium strains TA1535, TA1537, TA97, TA98 and TA100.

Executive summary:

In a publication entitled "Salmonella mutagenicity tests: IV. Results from the testing of 300 chemicals " (Environ Molec Mutagen, 11, Suppl.12 ,pg 1 -158, (1988);.Zeiger, E. et al), the in vitro mutagenic potential of 300 chemicals, including Octanoic acid (CAS 124 -07 -2), was investigated.

 

The study was assigned a reliability score of 2 in accordance with the criteria for assessing data quality set forth by Klimischet al. (1997) as study is well documented and the method described in the literature is similar to the guideline study with the exception that no strains which have an AT base pair at the primary revision site were tested.

Mutagenicity was investigated using the preincubation assay as part of a screening programme for the NTP. Under the conditions of the study Octanoic acid was found to be non-mutagenic, with and without metabolic activation, in Salmonella typhimurium strains TA1535, TA 1537, TA 97, TA98 and TA 100.