[The suppression of the repair of radio-induced DNA damage in Escherichia coli cells by indazolin derivatives and proksifein].

A study was made of the postradiation effect of five indasoline derivatives and proxyfeine on the survival rate and repair of DNA single-strand breaks in E. coli exposed to gamma-irradiation. Some indasoline derivatives (three substances) and proxyfeine added in postradiation medium in nontoxic concentrations decreased the survival rate of radioresistant strains WP2 hcr+, Hr30 and Hs30, but do not influence survival rate of radiosensitive mutant Bs-1. These substances inhibit the repair of DNA single-strand breaks in E. coli WP2 hcr+. Substances, which do not inhibit the survival rate of radioresistant strains, do not inhibit the repair of breaks. Proxyfeine in non-toxic concentrations in non-irradiated cells induces DNA degradation. Indazoline derivatives do not induce DNA degradation. Data presented suggest that indasolines are new class inhibitors of DNA repair. It is possible that proxyfeine is too an inhibitor of DNA repair.