Increased Local Metabolic Rate by Free Fatty Acids in the Intact Dog Heart

Abstract

Elevation of arterial concentration of free fatty acids (FFA) from an average of 450 to 3000 (δmo1/1, induced by intravenous (i. v.) infusion of a fat emulsion after heparinization, raised local metabolic rate in the left ventricular wall by an average of 18% (p > 0.025), without changes in heart rate, left ventricular systolic and end-diastolic pressures, or maximum rate of rise of left ventricular pressure (dP/dt). I. v. infusion of isoproterenol (2–3 δg/min) increased local metabolic rate by an average of 82% (p > 0.02) with a concomitant increase in arterial FFA concentration from an average of 450 to 1800 δmol/1. <By abolishing lipolysis with nicotinic acid, the metabolic heat production induced by isoproterenol was lowered by an average of 39% (p > 0.02), despite the fact that myocardial performance was not influenced by nicotinic acid. The data are consistent with the hypothesis that myocardial FFA metabolism plays a significant role in stimulating the oxygen demand of the heart.

Key Words:

• Free fatty acids
• isoproterenol
• lipolysis
• metabolic heat
• metabolism
• myocard
• nicotinic acid