MODULATING INFLUENCE OF INORGANIC ARSENIC ON THE RECOMBINOGENIC AND MUTAGENIC ACTION OF IONIZING-RADIATION AND ALKYLATING-AGENTS IN DROSOPHILA-MELANOGASTER

In bacterial systems and in mammalian in vitro cell cultures, inorgani c arsenic has been found to potentiate the mutagenic action of UV as w ell as of a number of mutagenic agents, probably by interfering with t he later steps of DNA-repair. The Drosophila wing spot test (SMART) wa s used to study the modulating action of inorganic arsenic on the reco mbinogenic and mutagenic effects of the alkylating agents ethylnitroso urea (ENU), methylmethane sulphonate (MMS), and ethylene oxide (EO) as well as of gamma-rays. It was found, that arsenic in this in vivo tes t system exerted an inhibitory effect on mitotic recombination induced by alkylating agents and gamma-irradiation. These results are in cont rast to the synergistic effect of inorganic arsenic on point mutations and deletions as reported for human lymphocytes and primary fibroblas ts. The reason for the discrepancy between the mammalian systems and D rosophila with respect to the modulating action of arsenic is discusse d.