[14C]palmitate uptake in isolated rat liver mitochondria: effects of fasting, diabetes mellitus, and inhibitors of carnitine acyltransferase.
The rapid association of Na-[16-(14)C]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 [(14)C]palmitate. At 6.5 micro M [(14)C]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 [(14)C]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.
D000217:Acyltransferases / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002210:Caprylates / Q000494:pharmacology; D002331:Carnitine / Q000031:analogs & derivatives / Q000494:pharmacology; D002333:Carnitine Acyltransferases / Q000037:antagonists & inhibitors*; D003065:Coenzyme A / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D016883:Diabetic Ketoacidosis / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D010168:Palmitates / Q000378:metabolism* / Q000494:pharmacology; D010169:Palmitic Acids / Q000378:metabolism*; D051381:Rats; D013217:Starvation
D002210:Caprylates; D010168:Palmitates; D010169:Palmitic Acids; C022776:2-bromopalmitate; D000255:Adenosine Triphosphate; D000217:Acyltransferases; D002333:Carnitine Acyltransferases; C008698:octanoylcarnitine; D002331:Carnitine; D003065:Coenzyme A