A study of the potential genotoxicity of cimetidine using human hepatocyte primary cultures: discrepancy from results obtained in rat hepatocytes.

The genotoxicity of cimetidine, a drug widely used in the treatment of peptic ulcer, was examined in human hepatocyte primary cultures. No induction of unscheduled DNA synthesis, as detected by autoradiography, or of DNA fragmentation, as measured by alkaline elution, was seen in metabolically competent human hepatocytes exposed for 20 h to cimetidine concentrations ranging from 0.33 to 9 mM. These findings, which are in contrast with the previously observed capability of cimetidine to induce DNA damage and repair in rat hepatocyte primary cultures, suggest that for some chemicals the rat hepatocyte model might be an inappropriate predictor of potential genotoxic effects in the analogous human cells.