Toxicity, mutagenicity and induction of recA protein in Escherichia coli treated with cis-diamminedichloroplatinum(II) and cis-diamminetetrachloroplatinum(IV).

After exposure of bacteria to equal concentrations of cis-diamminedichloroplatinum(II) (DDP) and cis-diamminetetrachloroplatinum(IV) (DTP), the intracellular concentration of DTP was an order of magnitude greater than DDP. However, at identical intracellular drug concentrations, the Pt(IV) compound formed only half as many platinum-DNA lesions. For equal numbers of DNA lesions, the toxicity of both agents was identical whereas the mutagenicity of DTP was 7 times less than for DDP and its capacity to induce recA protein was less than DDP by a factor of 3.5. Bioreduction of Pt(IV) compounds to their corresponding Pt(II) analogues has been proposed as a mechanism for the reaction of Pt(IV) compounds with cellular DNA. According to this hypothesis, DTP would be reduced to DDP in the cell prior to its reaction with DNA and the platinum-DNA lesions of the two compounds should be identical. Our results suggest that reductive elimination can not entirely account for DNA damage caused by PT(IV) compounds in bacteria.