Genotoxicity testing of potassium canrenoate in cultured rat and human cells

Potassium canrenoate (PC), a competitive aldosterone antagonist used as a d iuretic and in the treatment of hypertension, was examined for its capacity to produce genotoxic effects in cultured rat and human cells. At subtoxic concentrations (10-90 mu M) PC was found to induce a dose-dependent degree of DNA fragmentation, as detected by the Comet assay, and of DNA repair syn thesis, as measured by quantitative autoradiography, in primary cultures of hepatocytes from rat and human donors of both genders. In rat hepatocytes both DNA fragmentation and DNA repair were more marked after 3 h than after 20 h exposure and in cultures from females than from males. In human hepat ocytes from one male and two female donors, PC caused a similar effect in t erms of DNA fragmentation, whereas DNA repair was detected in cultures from only two of the same three donors and was less marked than in rat hepatocy tes. A modest but statistically significant increase in micronucleated cell s was present in primary cultures of replicating rat hepatocytes exposed to 10 or 30 mu M PC for 48 h, the response being, in this case also, more evi dent in females than in males. In contrast, PC did not induce micronucleus formation in human hepatocytes from two female donors. Any evidence of DNA fragmentation and micronucleus formation was absent in cultured human lymph ocytes, Taken as a whole these findings support the hypothesis that hepatoc ytes activate PC to DNA-damaging reactive species. PC induced the observed genotoxic effects at concentrations close to those produced in humans by th e administration of therapeutic doses, but these effects were as a whole mo re marked in rat than in human hepatocytes, Since PC shares the 17-hydroxy- 3-oxopregna-4,6-diene structure with cyproterone acetate, chlormadinone ace tate and megestrol acetate, previously found to be genotoxic to both rat an d human hepatocytes, the potential carcinogenic hazard of this type of ster oids cannot be neglected.