Myocardial lactate oxidation and release in the dog in vivo.

Abstract

Myocardial metabolism of lactate was studied in eight, anesthetized, non-heparinized, open-chest dogs maintained on positive pressure breathing with room air. Arterial and coronary sinus (CS) samples were obtained during a constant intravenous infusion of 2-C14-l-lactate, and were analyzed for chemical and radiochemical content of lactate, pyruvate, glucose and CO2, as well as chemical content of oxygen. The specific activity (dpm/μM) of lactate in CS blood was lower than that in the arterial samples. These differences are consistent with the addition of cold, unlabelled lactate to the CS blood by the myocardium. This lactate release amounted to 35.0±6.1% of the A-CS lactate uptake. Oxidation of lactate by the heart, which was measured from C14O2 production amounted to 45.9% of the myocardial oxygen uptake, after a correction was made for secondary labelling of pyruvate and glucose.