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This publication includes data of Salmonella mutagenicity results on 270 coded chemicals, encompassing 329 tests performed by three laboratories under contract to the National Toxicology Program (NTP). The preincubation modification of the Salmonella/mammalian microsome assay was used to test chemicals in up to five Salmonella strains in the presence and absence of rat and hamster liver S-9. With a few exceptions, inter- and intralaboratory reproducibility was good.

The results and data from the testing of 255 chemicals for mutagenicity in Salmonella are presented. All chemicals were tested under code using a preincubation modification of the Salmonella/microsome test in the absence of exogenous metabolic activation and in the presence of liver S-9 from Aroclor-induced male Sprague-Dawley rats and Syrian hamsters.

The results and data from the testing of 255 chemicals for mutagenicity in Salmonella are presented. All chemicals were tested under code using a preincubation modification of the Sulmonellalmicrosome test in the absence of exogenous metabolic activation and in the presence of liver S-9 from Aroclor-induced male Sprague-Dawley rats and Syrian hamsters. Key words: metabolic activation, Ames test, National Toxicology Program INTRODUCTIONA number of in vitro and in vivo test systems are being used in the National Toxicology Program (NTP) to evaluate chemicals for their ability to induce mutations , chromosome damage, and DNA damage. The rationale for testing has been described in detail elsewhere [Zeiger and Drake, 19801. The purpose of this report is to present the results and data from the testing of 255 chemicals for their ability to induce mutations in Salmonella. Because some chemicals were tested in more than one laboratory or at different times within the same laboratory, a total of 291 individual samples were tested. MATERIALS AND METHODS ChemicalsThe chemicals tested, their sources, and purities (where known) are listed in Table I; the chemical structures are presented in Appendix 1. The laboratories were supplied with the chemicals, which were coded by the NTP chemical repository (Radian Corp., Austin, TX), along with information on the physical characteristics of the chemicals, their solubility in different solvents, and safety and decontamination information. Also supplied, but in sealed envelopes, was information on the identity and toxicity of the chemicals. This was to be used in the event of a spill or personnel exposure. All coded chemicals were handled as potential mutagens and carcinogens.A number of chemicals were tested in more than one laboratory or at different times in the same laboratory. When this occurred, the laboratory performing the retest was not informed of the identity of the chemical or that it had been tested previously.The solvent of choice was distilled water, followed by dimethyl sulfoxide, 95% ethanol, and acetone. The individual laboratories made independent assessments of the solvents to be used. Bacterial StrainsAll chemicals were tested in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 and/or TA97. The majority of chemicals were tested in TA1537, and a few were tested in TA97. The testing in both strains is the result of an evolution of the protocol described by Haworth et a1 [1983]. In this original protocol, TA1537 was used. In a later protocol, TA97 replaced TA1537, but the option to retest a chemical in TA1537 was retained for chemicals that produced a positive or questionable response in TA97 and negative responses in the other strains.All strains were obtained from Dr. Bruce Ames (University of California, Berkeley) and were stored as recommended [Maron and Ames, 19831. Prior to their use for mutagenicity assays, all cultures were grown overnight with shaking at 37°C in Oxoid broth, and their phenotypes were analyzed, Preparation of Liver S-9 Fraction...

Saccharomyces cerevisiae.observations we tested 1-methyl-2-pyrrolidinone i n s t r a i n D61.M o f S, cerevisiae and found t h a t i t too induced aneuploidy. Subsequent investigations w i t h several s t r u c t u r a l l y r e l a t e d compounds revealed t h a t 2-pyrrol idinone also induced aneuploidy but succinimide, pyrrolidine, 1-methyl p y r r o l i d i n e , 1-methyl-3-pyrrolidinol, and l-methyl-2-pyrrolidineethanol d i d not. Maleimide and the N-hydroxy-, N-methyl-, and N-ethyl-derivatives were also negative f o r aneuploidy induction. 2-PYRROLIDINONE AND 1-METHYL-2-PYRROLIDINONE INDUCE ANEUPLOIDY I NA number o f solvent compounds have been shown t o induce aneuploidy i nAs an extension o f these previous 140 AN