Direct effects of adriamycin on the rat heart sarcolemma

Effects of adriamycin on rat heart sarcolemma were investigated by determining several membrane enzyme activities in the absence or presence of different concentrations of the drug. The adenylate cyclase activity was found to be stimulated by 0.001 and 0.01 microM of adriamycin whereas this enzyme activity was inhibited at 100 and 1000 microM concentrations of the drug. Magnesium dependent Na+, K+ ATPase was not effected by adriamycin, however, in presence of 2 mM ouabain, adriamycin (100 microM) had a depressant effect on the Na+, K+ ATPase activity. Ca2+ ATPase activity was found to be stimulated by adriamycin. The drug had no effect on the Mg2+ ATPase and 5'-nucleotidase activities. These data suggest direct as well as specific effects of adriamycin which may be important in drug-induced cardiotoxicity.