Mutagenicity of 7,12-dimethylbenz[a]anthracene and some other aromatic mutagens in Drosophila melanogaster.

The optimal conditions for mutagenesis studies with DMBA and some other aromatic carcinogens in Drosophila were investigated in detail. The results presented in this paper indicate the following. The mutagenic effectiveness of DMBA is dependent on the route of administration, injection being far more effective when compared with feeding. The choice of the solvent is a crucial experimental condition. DMBA, when dissolved in oil/DMF, is ineffective whereas a special fat emulsion of DMBA gives high mutation frequencies. There appears to be an extreme strain dependence in the mutagenicity of DMBA. Mutagenic effectiveness in strain Berlin-K was rather low, whereas Oregon-K and Karsnäs-60 proved to be very susceptible to DMBA. Under the conditions of test, DMBA did not induce loss of a ring-X chromosome and did not produce recessive lethal mutations in such a chromosome. DMBA did not produce 2-3 translocations to any significant extent. An increase in DMBA-induced recessive lethal mutations was found upon storage of treated sperm with an optimal storage time of 4-10 days. DMBA is efficient in the production of delayed recessive lethal mutations in strain Berlin-K. Twice as many lethals were recovered with the F3 generation as compared with those in F2. In strain Oregon-K, where the frequency of F2 lethals was much higher than in strain Berlin-K, the ratio of F3/F2 lethals was clearly lower. Enzyme induction with phenobarbital reduces the mutagenic effectiveness of DMBA. Whereas TMBA was not mutagenic in Berlin-K, considerable mutagenicity was observed in Oregon-K and Karsnäs-60. Injection of carcinogenic polycyclic aromatic hydrocarbons and aromatic amines, when dissolved in special fat emulsions, enhances the mutagenic effectiveness of some compounds (DMBA, TMBA, DA and AcO-AAF), but this procedure does not always solve the problems pertinent to these classes of promutagens in Drosophila.