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Key value for chemical safety assessment

Additional information

In vitro Studies

Bacterial Mutagenicity  

There are two available bacterial mutagenicity assays conducted with AMP in Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 (Wagner, 1996; Baldwin 1976). IN the key study (Wagner, 1996) an initial and confirmatory assay was used to evaluate the mutagenic potential of the test material.  A minimum of 5 dose levels of the test article, with vehicle and positive controls, were plated with tester strains in the presence and absence of rat liver S9 activation.  All dose levels of test article, vehicle controls, and positive controls were plated in triplicate.  The test systems were exposed to the test article via the plate incorporation methodology. Neither precipitate nor appreciable toxicity was observed in the initial or confirmatory assays.  In neither the initial nor confirmatory assay was there a positive response with any of the tester strains at any dose level, in the presence or absence of S9 activation.  The mean of each positive control exhibited at least a 3-fold increase in the number of revertants over the mean value of the respective vehicle control, indicating a valid test. The results of the supporting study (Baldwin 1976) corroborate those of the key study, confirming a lack of bacterial mutagenicity.

Gene Mutation, Mammalian Cells   

An OECD 476 study was conducted with AMP (San and Clark, 1997).  L5178Y mouse lymphoma cells were exposed to the vehicle alone and solutions of the test article at concentrations of 0.5, 1.5, 5.0, 15, 50, 150, 500, 1500, 5000 ug/mL were prepared in both the absence and presence of S9.  Positive controls, with and without S9, were tested concurrently following a preliminary assay.  No treated cultures exhibited mutant frequencies more than 55 mutants per 10^6 clonable cells over the solvent control.  A dose-response trend was not observed in either the activated or non-activated systems, and the independent repeat of the assay showed similar results.  The study is considered valid, and AMP is therefore considered negative in the gene mutation assay with mammalian cells.

 In vivo Studies

Chromosomal Aberrations, Micronucleus Test   

An OECD 474 (mouse micronucleus) test was conducted with AMP according to GLP’s at dose levels of 16, 30, and 60 mg/kg by a single IP injection; the positive control (cyclophosphamide) was administered in the same manner concurrently (Gudi, 1998).  At the scheduled sacrifice times (24 and 48 hours), marrow from the femurs of 5 mice / sex / dose were extracted, and slides were prepared of the bone marrow cells.  Using oil immersion, 2000 polychromatic erythrocytes were scored for the presence of micronuclei.  The number of micronucleated normochromatic erythrocytes in the field of 2000 polychromatic erythrocytes was enumerated.  The proportion of polychromatic erythrocytes to total erythrocytes was also recorded per 1000 erythrocytes.  There was no treatment-related mortality at any dose level.  Clinical signs noted on the day of dosing were limited to lethargy in males and females at 60 mg/kg (highest dose).  The number of micronucleated polychromatic erythrocytes per 2000 polychromatic erythrocytes in test article-treated groups was not statistically increased relative to their respective vehicle control in either male of female mice, regardless of dose level or bone marrow collection time.

Conclusion

AMP lacked genotoxicity in the bacterial reverse mutation assay, the mammalian cell gene mutation assay, and a mouse micronucleus study.

Short description of key information:
Mutagenicity tests with AMP have included an OECD 471 guideline bacterial reverse mutation assay (Wagner, 1996), an OECD 476 mammalian cell gene mutation assay (San and Clark, 1997), and an OECD 474 mouse micronucleus study (Gudi, 1998). Mutagenicity tests have also been conducted using the Ames assay in Salmonella typhimurium and a mutagenicity assay in Saccharomyces cerevisiae D-4 (Baldwin, 1976).

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Data clearly demonstrate that AMP is not genotoxic or clastogenic in vitro and in vivo