title: Calcium binding to cardiac sarcolemma.
abstract: Studies with a sarcolemma preparation from guinea pig hearts revealed two classes of Ca2+ binding sites: high affinity sites (Km' of 16 muM) and a 10-fold greater number of low affinity sites (Km' of 800 muM). Low affinity Ca2+ binding was inhibited by ruthenium red and verapamil, suggesting that these sites are located on the external side of the membrane. However, clear-cut competition between H+ and Ca2+ could not be demonstrated with isolated sarcolemma.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002474:Cell-Free System; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D008297:Male; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D012430:Ruthenium Red / Q000494:pharmacology; D012508:Sarcolemma / Q000201:enzymology / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D012430:Ruthenium Red; D014700:Verapamil; D000262:Adenylyl Cyclases; D002118:Calcium