Heart sarcolemmal ATPase and calcium binding activities in rats fed a high cholesterol diet.
ATPase and calcium binding activities were studied in sarcolemmal membranes from hearts of male rats fed either a control or 2% cholesterol diet for different time periods. Studies with isolated membrane revealed a significant increase in Na+-K+ ATPase activity, sialic acid content and ATP-independent calcium binding capacity in the presence of 1.25 mM CaCl2 in the 6 week cholesterol fed group. By 12 weeks, Na+-K+ ATPase, Mg2+-ATPase and Ca2+-ATPase activities as well as ATP-independent calcium binding in the presence of 0.05 mM CaCl2 were increased in membranes from cholesterol fed rats. A significant increase (P less than 0.05) in the sarcolemmal cholesterol/phospholipid molar ratio, which is an indicator of a decrease in membrane fluidity, was also noted in the 12 week cholesterol fed group. Concanavalin A, which is believed to decrease membrane fluidity, stimulated both Mg2+ and Ca2+-dependent ATPase activities and increased ATP-independent calcium binding in control sarcolemmal preparations and these changes resembled those observed in the sarcolemma from cholesterol fed rats. Since concanavalin A did not alter the activity of Na+-K+ ATPase, it appears that some of the observed differences in sarcolemmal activities upon cholesterol feeding did not correlate well with changes in membrane order. At 24 weeks, there was a generalized depression in the sarcolemmal ATPase activities of the cholesterol group; both Mg2+ ATPase and Ca2+ ATPase were significantly less than in control.(ABSTRACT TRUNCATED AT 250 WORDS)
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D002791:Cholesterol, Dietary / Q000009:adverse effects*; D003327:Coronary Disease / Q000201:enzymology; D004789:Enzyme Activation; D008297:Male; D008560:Membrane Fluidity; D009206:Myocardium / Q000201:enzymology*; D019158:N-Acetylneuraminic Acid; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000201:enzymology*; D012794:Sialic Acids / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002791:Cholesterol, Dietary; D010743:Phospholipids; D012794:Sialic Acids; D002784:Cholesterol; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D019158:N-Acetylneuraminic Acid; D002118:Calcium