Altered active sodium and calcium transport by heart sarcolemmal membranes from young spontaneously hypertensive rats: modulation by calmodulin.
Active transport of Na+,K+ and Ca2+ was compared in heart plasma membranes from 3-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). ATP-dependent Ca2+ accumulation, which reflects Ca2+, Mg2+-ATPase activity, was higher in SHR than in WKY membranes. At a free calcium concentration of 4 X 10(-7)M, the addition of 2 X 10(-7)M calmodulin enhanced the active Ca2+-transport more in WKY than in SHR vesicles. Na+- and K+-dependent ATPase activity was two fold higher in SHR than in WKY. From ouabain binding studies this seemed to be due to an increased density of enzyme units. Physiological concentrations of calmodulin and calcium ions reduced Na+,K+-ATPase activity in the two strains but more in SHR than in WKY. This study demonstrates that active Na+ and Ca2+ transport is enhanced in young SHR; the Ca2+-calmodulin complex may regulate Na+,K+-ATPase activity and sensitivity of Na+,K+-ATPase and Ca2+,Mg2+-ATPase activities to Ca2+-calmodulin differs between SHR and WKY.
D000375:Aging; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D007473:Ion Channels / Q000201:enzymology; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D051381:Rats; D011918:Rats, Inbred SHR / Q000378:metabolism*; D011919:Rats, Inbred Strains / Q000378:metabolism*; D011921:Rats, Inbred WKY; D012508:Sarcolemma / Q000201:enzymology*; D012964:Sodium / Q000378:metabolism*
D002147:Calmodulin; D007473:Ion Channels; D012964:Sodium; D002118:Calcium