Effects of sodium pentobarbital on rat heart sarcolemma

The effects of sodium pentobarbital on ATPase, Ca2+ binding and adenylate cyclase activities of the rat heart sarcolemmal preparations were investigated. The Na+ - K+ ATPase activity was diminished by pentobarbital in concentrations as low as 0.3 mM. Mg2+ ATPase, Ca2+ ATPase and adenylate cyclase activities were also depressed but required 10 to 15 mM of this agent. Pentobarbital in concentrations of 10 mM, however, caused an increase in sarcolemmal Ca2+ binding. Mitochondrial and microsomal ATPase activities were decreased by 1 and 5 mM concentrations of pentobarbital respectively, while myofibrillar ATPase activity was unaltered even at a concentration of 20 mM. These data suggest that cardiodepressant effects of high doses of pentobarbital may partly be explained on the basis of its actions on heart sarcolemma.