Isolation and enzymatic characterization of guinea pig cardiac sarcolemma.
Sarcolemma was isolated by fractionation of salt-extracted particles on two consecutive sucrose density gradients. Salt extraction of homogenates, rather than of washed particles, was found to preserve the activities of adenylate cyclase and ouabain-sensitive (Na+,-K+)-ATPase in the isolated sarcolemmal membranes. Purified sarcolemma contained substantial adenylate cyclase and guanylate cyclase activities that were stimulable by beta-adrenergic and muscarinic agonists, respectively. Significant ouabain-sensitive (Na+, K+)-ATPase activity as well as putative digitalis receptor activity was also present in sarcolemma. Cyclic nucleotide phosphodiesterases of sarcolemma, both cAMP- and cGMP-dependent, displayed positive cooperativity of substrate interactions; Ca2+ ions were found to increase the activity of the GMP-dependent enzyme.
D000251:Adenosine Triphosphatases / Q000032:analysis; D000262:Adenylyl Cyclases / Q000032:analysis; D000818:Animals; D002458:Cell Fractionation; D006162:Guanylate Cyclase / Q000032:analysis; D006168:Guinea Pigs; D009206:Myocardium / Q000201:enzymology / Q000648:ultrastructure*; D010042:Ouabain / Q000378:metabolism / Q000494:pharmacology; D012508:Sarcolemma / Q000201:enzymology / Q000648:ultrastructure*
D010042:Ouabain; D000251:Adenosine Triphosphatases; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase