Chemical mutagenesis testing in Drosophila. VI. Interlaboratory comparison of mutagenicity tests after treatment of larvae.

Previous publications on the National Toxicology Program (NTP)-sponsored mutagenicity testing program in Drosophila dealt with evaluations of chemicals following adult treatment (feed, injection). The current paper deals with a comparison between the laboratories at Brown University (BRU) and the University of Wisconsin at Madison (UWM) regarding the response of larvae to treatment with chemicals in the sex-linked recessive lethal (SLRL) test and, where appropriate, the reciprocal translocation test as well. Dimethylnitrosamine (DMN) and dimethylbenz(a)anthracene were used first as reference mutagens. Six coded compounds were then evaluated regarding their repeatability in the two laboratories; the compounds were benzo(a)pyrene, 3-methylcholanthrene, coumarin, quinoline, formaldehyde, and 9-aminoacridine. It was concluded that at this time it would be imprudent to forgo larval treatment in cases where compounds proved negative after adult feeding. Accordingly, testing a series of 20 compounds negative after adult treatment is in progress.