STRONG INTRASPECIES VARIABILITY IN THE METABOLIC CONVERSION OF 6 PROCARCINOGENS TO SOMATIC-CELL RECOMBINAGENS IN DROSOPHILA

Genetic heterogeneity in response to genotoxic carcinogens requiring m etabolic conversion has been studied in Drosophila, using seven differ ent genotypes in combination with the w/w+ eye mosaic assay for mitoti c recombination. The set of tester strains examined consisted of four wild-type laboratory strains (Berlin-K, BK; Oregon-K, OK; Leiden-S, LS ; and 91-C), and three DDT-resistant strains (91-R; Hikone-R, HR; and Haag-79, HG). Drosophila larvae heterozygous for the wild-type report gene w+ were exposed to benz[a]anthracene (BA), benzo[a]pyrene (BP), 9 ,10-dimethylanthracene (DA), monocrotaline (MC), N-nitrosodimethylamin e (DMN) or vinyl bromide (VBr). The primary conclusion regarding this study is the up to 60-fold variation between different genotypes in mo saic spot frequencies induced by those procarcinogens and the non-exis tence of just one genotype to function as a 'super-strain' in the acti vation of different classes of procarcinogens. By contrast, the seven Drosophila strains show a similar response to the direct-acting agent methyl methanesulphonate. Among the six procarcinogens selected for th is study, DMN and MC are readily detectable in all the distinct genoty pes. Less satisfactory in terms of test performance are the either neg ative or weak test responses with BA in all four-wild type strains (LS , BK, OK and 91-C), and the weakly positive results for vinyl bromide in LS, BK and OK. The best overall test response was provided by strai ns HG and HR. It is concluded that the combined application of strains HG and HR safely and reliably should detect somatic cell recombinagen s in the Drosophila w/w+ system. Addition of a third tester strain is not suggested by the test results obtained so far.