Studies on cytotoxic and genotoxic effects of N-hydroxypyridine-2-thione (Omadine) in L5178Y mouse lymphoma cells.

The cytotoxicity and genotoxicity of the antifungal and antimicrobial agent Omadine, i.e. N-hydroxypyridine-2-thione (HOPT), has been investigated in L5178Y mouse lymphoma cells in the dark and under UVA irradiation. Omadine inhibits cell growth and induces micronuclei at concentrations >0.5 microM in the absence of light. At a 0.5-microM concentration, an UVA-dose-dependent induction of micronuclei is observed, conditions at which the cytotoxicity and genotoxicity in the dark is negligible. The photogenotoxicity is not accompanied by cytotoxicity. Control experiments with the radical scavengers GSH and GSHOEt implicate the involvement of hydroxyl radicals in the photogenotoxicity of Omadine.