[Effect of bleomycin on DNA-dependent RNA polymerase purified from normal and neoplastic tissues].

The effect of bleomycin was investigated using two forms of DNA-dependent RNA polymerase (A and B) purified from normal tissues and experimental tumours in presence either of Mn2+ or Mg2+ and native or denatured homologous DNA. THe results show that the antibiotic inhibits the enzyme activity of both classes, and the degree of inhibition appears to be influenced by the nature of cation, the highest values being reached with Mg2+. Moreover, the denaturation of DNA modify the bleomycin effect significantly. With regard to cellular damage induced by the drug, the data here reported show that there is not a substantial difference between normal and tumour tissues.