Journal of Lipid Research, Vol. 19, 688-694, August 1978
Copyright © 1978 by Lipid Research, Inc.

[¹⁴C]Palmitate uptake in isolated rat liver mitochondria: effects of fasting, diabetes mellitus, and inhibitors of carnitine acyltransferase

John M. Amatruda , Dean H. Lockwood , Simeon Margolis , and Lutz A. Kiesow

Clayton Laboratories, Department of Medicine, The Johns Hopkins University, Baltimore, MD 21205, and The Department of Experimental Medicine, Naval Medical Research Institute, Bethesda, MD 20014

The rapid association of Na-[16-¹⁴C]palmitate with isolated rat liver mitochondria was measured by an oil separation method. This association was time and temperature-dependent and was absolutely dependent on the presence of exogenous ATP and CoASH and partially dependent on exogenous carnitine. Carnitine dependence was enhanced at lower concentrations of [¹⁴C]palmitate. At 6.5 µM [¹⁴C]palmitate (molar ratio of palmitate to albumin equal to 0.54), the rate of association was linear for 20 sec and was increased more than 100% in the presence of carnitine. Carnitine-dependent association was inhibited by 2-bromopalmitate, an inhibitor of carnitine acyltransferase I, but not by (+)-octanoylcarnitine, a presumed inhibitor of carnitine acyltransferase II. The association of [¹⁴C]palmitate with mitochondria was enhanced from 190 to 330% in mitochondria isolated from fasted animals and from 160 to 230% in mitochondria isolated from diabetic, ketotic animals as compared to control animals. The enhanced association with mitochondria from fasted animals was inhibited by 2-bromopalmitate. These studies demonstrate a method of evaluating fatty acid association with mitochondria which, because of its dependence on carnitine and carnitine acyltransferase I activity, most likely represents true uptake into mitochondria. Furthermore, these studies indicate that the carnitine-dependent uptake of fatty acids into mitochondria is enhanced in the two ketotic states evaluated and that the carnitine acyltransferase system may be a regulatory site in ketone body production.

Supplementary key words fatty acid uptake • ketone bodies

Submitted on July 29, 1977
Revised on November 7, 1977
Accepted on March 3, 1978

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