Effects of dl-erythro-1-phenoxy-3-[(3,4-dimethoxyphenethyl)-amino]-butan-2-ol (PS-6) on rat heart sarcolemma.

Effects of dl-erythro-1-phenoxy-3-[(3,4-dimethoxyphenethyl)-amino]-butan-2-ol (PS-6) on ATPase and calcium binding activities of rat heart sarcolemma as well as adenylate cyclase of both sarcolemma and heart washed particles were studied under in vitro conditions. PS-6 at concentrations of 10(-7) mol/l or higher inhibited Na+-K+ ATPase and calcium binding activities significantly. The inhibition of calcium binding activity was dependent upon the concentration of calcium in the incubation medium with greater percentage inhibition seen at lower concentrations. While basal adenylate cyclase activity was not affected by 10(-7)--10(-4) mol/l, isoprenaline stimulated adenylate cyclase activity was inhibited by 10(-6) mol/l or higher concentrations of PS-6. At 10(-3) mol/l PS-6 a more generalized inhibitory effect was seen, with all parameters studied being inhibited. These results suggest that sarcolemma is one of the sites for the cardiac actions of PS-6.