Enhancement of the activity of bleomycin by cysteamine in a micronucleus assay in G0 human lymphocytes.

The aminothiol cysteamine enhances the induction of micronuclei by bleomycin in G0 human lymphocytes. The potentiation of bleomycin (12.5, 25, 50, or 100 micrograms/ml) increased with cysteamine concentration from 5 to 20 mM in a 2-h treatment before culturing the cells for the cytokinesis-block assay. The maximum clastogenic activity of bleomycin in the presence of cysteamine was more than 10-fold greater than that of the same dosage of bleomycin alone. Both the thiol and amine functions of aminothiols seem to contribute to the potentiation of bleomycin.