Induction of chromosomal aberrations by the rhodium(III) complex cis-[Rh(biq)(2)Cl-2]Cl in cultured human lymphocytes

The genotoxicity of the rhodium(III) complex cis-[Rh(biq)(2)Cl-2]Cl (comple x R) in cultured human lymphocytes was studied using the chromosome aberrat ions (CAs) assay. Lymphocyte cultures were initiated from two adult healthy non-smoking male volunteers and were exposed to the complex for a duration of 3 or 20 h prior to cell collection. The reduction in mitotic indices (M I) and the induction of CAs represented the toxic and clastogenic effects o f the different treatments, respectively. Complex R proved to be an interme diate toxic clastogen with a MI50 of 1.0 mu g/ml and a minimum positive dos e (MPD) of 0.1 mu g/ml. Like bleomycin, complex R exerted its clastogenic e ffects without the need for metabolic activation and induced CAs of all typ es in lymphocytes treated in the G(2) and late S phases and, therefore, can be considered a radiomimetic. In addition, it induced more total CAs of ch romatid-type than of chromosome-type. The reduction in the frequencies of C As following the 20 h treatment as compared with those induced following th e 3 h treatments indicated that human lymphocytes in the presence of comple x R can partially tolerate the lesions involved in CA production. Based on the biological effects of complex R and the similarities between its functi onal group and that of bleomycin, possible mechanisms for complex R genotox icity are discussed.