The genotoxicities of N-nitrosamines in Drosophila melanogaster in vivo: the correlation of mutagenicity in the wing spot test with the DNA damages detected by the DNA-repair test

The genotoxicities of a series of N-nitrosamines were assayed in the wing spot test and a new short-term test of Drosophila melanogaster. In the spot test, larval flies trans-heterozygous for the somatic cell markers mwh and flr³ were fed the test reagents and the wing hairs in adults were inspected for clones expressing the phenotypes of the markers. In the other test, larval stock consisting of meiotic recombination-deficient (Rec^-) double mutant mei-9^a and mei-41^D5 males and repair-proficient Rec⁺ females were grown on feed containing the reagents and the DNA damages were detected with the preferential killing of the Rec^- larvae as an endpoint. The carcinogenic nitrosamines tested, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-butylamine (NDBA), N-nitrosomorpholine (NMOR), N-nitrosopiperidine (NPIP) and N-nitrosopyrrolidine (NPYR), all showed clearly positive activities in both tests. The activities in the wing spot test were ranked in a sequence of NDMA ≫ NMOR > NPIP > NDEA NPYR > NDBA. A similar ranking was obtained in the repair assay. The genotoxicity of N-nitrosodiphyenylamine (NDPhA), carcinogenicity studies of which are inconclusive, was marginal in the spot test. The non-carcinogenic N-nitrosoproline (NPRO) and the non-mutagenic N-nitrosothioproline (NTPRO) were negative in the spot test. NDPhA and NPRO were negative in the repair test as well. The DNA-repair test is thus a convenient technique for estimating the mutagenicity of compounds because of its simplicity compared with the wing spot test. These Drosophila tests may be useful in predicting carcinogenic potentials of compounds.