Effect of free fatty acid on the oxygen consumption of perfused rat heart

Abstract

The effect of substrates on O2, was studied in isolated rat hearts perfused by a modified Langendorff technique. qO2 was stimulated by albumin-bound palmitate or octanoate at high free fatty acid-albumin [image] ratios but not by 3,3,12,12-tetra-methylmyristate (a nonoxidizable fatty acid analogue) or by glucose and insulin. The increase in qO2 caused by perfusion with high concentrations of palmitate was accompanied by an increase in oxidation of perfusate palmitate-1-C14 to C1402. The increase in palmitate-1-C14 oxidation accounted for at least 73% of the increment in O2 consumption. Perfusion of the beating heart at high concentrations of free fatty acids (FFA) increased coronary flow rate at constant perfusion pressure. Control studies showed that increasing coronary flow rate at a fixed FFA concentration in the perfusate increased qO2, but this effect was relatively small. Palmitate and octanoate stimulated qO2 in the K-arrested heart perfused at a fixed flow rate, eliminating the possiblity that the effect was dependent on myocardial work or changes in coronary flow rate. Thus the studies demonstrate what may be termed a "metabolic" stimulation by FFA. The possible mechanisms underlying these effects and their relevance to physiologic control of myocardial metabolism are discussed.