Stimulation of sodium-calcium exchange by cholesterol incorporation into isolated cardiac sarcolemmal vesicles.

摘要: Modification of the cholesterol content highly purified cardiac sarcolemma from dog ventricles was accomplished by incubation with phosphatidylcholine liposomes containing various amounts cholesterol. The degree enrichment could be varied changing liposomal cholesterol/phospholipid ratio or varying liposome-membrane time. Na+-Ca2+ exchange measured in cholesterol-enriched sarcolemmal vesicles increased up to 48% over control values. stimulation associated an affinity exchanger for Ca2+ (Km = 17 microM compared Km 22 preparations). cholesterol-depleted membrane preparations decreased 15%. This depressed activity a 27 microM). These changes were not due either change permeability increase amount bound vesicles. stimulating effect specific process since Ca2+-Mg2+ ATPase 40% enrichment. Further, K+-p-nitrophenylphosphatase and Na+-K+ activities both In situ oxidation completely eliminated exchange. results suggest that is intimately may interact protein modulate its activity.