Mutagenic effects of psoralens in yeast and V79 Chinese hamster cells

The mutagenic effects of monofunctional and bifunctional furocoumarins (psoralens) plus 365 nm radiation were analyzed in the yeast Saccharomyces cerevisiae. Per unit dose of 365-nm radiation, bifunctional compounds were more effective than were the monofunctional for the induction of reverse and forward mutations. The same was observed for the induction of 6-thioguanine-resistant mutants in V79 Chinese hamster cells when we compared the activity of 8-methoxypsoralen and 3-carbethoxypsoralen. An analysis of the kinetics of mutation induction indicated that DNA interstrand cross-links induced by bifunctional psoralens are more prone to error than are monoadducts induced by monofunctional psoralens. In yeast, 8-methoxypsoralen and 4,5'-dimethylangelicin were shown to photoinduce mitotic and nondisjunction. The implications of these findings for the use of psoralens in photochemotherapy and cosmetics are discussed.