Myocardial free fatty acid in unanesthetized dogs at rest and during exercise.

MILLER,HARVEY I., KEUKY.YUM,AND BEATRICE C.DURHAM. Myocardial free fatty acid in unanesthetized dogs at rest and during exercise. Am. J. Physiol. 220(3) : 589-596. 197 1 .-Myocardial free fatty acid (FFA) metabolism was studied in unanesthetized dogs at various plasma FFA concentrations. Exercise and norepinephrine (NE) infusion were used to raise the FFA level while glucose infusion was used to lower it. Correlation between FFA level and myocardial uptake was confirmed, and correlation between myocardial FFA removal and oxidation was shown at rest and during exercise. Isotopic palmitic acid was used to determine oxidation in heart muscle. There was no difference between arterial and coronary sinus FFA specific activity. Norepinephrine, while increasing FFA level greatly, did not increase myocardial oxidation as much. Plasma FFA accounted for 35% of the oxygen consumption of the heart during rest, about 750/, during exercise or NE infusion, and about 26% during glucose infusion. Lactic acid was taken up by the heart in the control and was changed to an output during NE infusion in some cases, decreased during glucose infusion, and was unaffected by exercise. Myocardial arteriovenous triglyceride differences were also very small. The myocardium oxidized virtually 100% of the FFA extracted from the plasma.