In vitro effects of palmitylcarnitine on cardiac plasma membrane Na,K-ATPase, and sarcoplasmic reticulum Ca2+-ATPase and Ca2+ transport

Adams, R.J.; Cohen, D.W.; Gupte, S.; Johnson, J.D.; Wallick, E.T.; Wang, T.; Schwartz, A.

Journal of Biological Chemistry 254(24): 12404-12410

1979


ISSN/ISBN: 0021-9258
PMID: 227894
Accession: 068524842

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Abstract
Palmitylcarnitine, an endogenous long-chain fatty acyl ester, produced marked changes in the structure and function of cardiac sarcoplasmic reticulum and sarcolemmal Na,K-ATPase isolated from canine ventricular muscle. Low concentrations (5-50 .mu.M) of palmitylcarnitine enhance Ca2+-ATPase activity and Ca2+ binding to sarcoplasmic reticulum and enhance [3H]ouabain binding to Na,K-ATPase above equilibrium binding levels but inhibit Na,K-ATPase hydrolytic activity. Increasing concentrations of palmitylcarnitine (50-200 .mu.M) further inhibit Na,K-ATPase activity and markedly decrease the binding of [3H]ouabain to this enzyme. Sarcoplasmic reticulum Ca2+-ATPase activity and Ca2+ binding are similarly inhibited by these higher concentrations of palmitylcarnitine. Palmitylcarnitine also produced concentration-dependent changes in the fluorescence intensity of a lipid-bound fluorescent probe, dansyl (5-dimethylaminonaphthalene-1-sulfonyl) phosphatidylethanolamine, which was incorporated into sarcoplasmic reticulum and Na,K-ATPase membranes. Palmitylcarnitine induced an enhancement of fluorescence in both membrane systems and this enhancement of fluorescence was linearly related to the inhibition of Na,K-ATPase activity. The biphasic action of palmitylcarnitine on the functional properties of sarcoplasmic reticulum and Na,K-ATPase resembles the actions of detergents on these membrane systems. Palmitylcarnitine acts as a naturally occurring detergent and a mechanism is proposed to explain its actions in vitro.