Metabolism of Cardiac Mi-scle

Thcrc is good evidence that pyruvate and lactate are important sources of cncrgy for the intact heart. Early studies by Himwich cl al. (1) in the> open chest dog and by McGinty and Miller (2) in the heart-lung preparation showed that lactate was removed from the coronary blood during its perfusion of the myocardium. Subsequent studies by Braun-Menendez et al. (3) with the isolated circulating heart showed that blood pyruvate was also extracted by the intact heart. More recent investigations of myocardial metabolism in the intact, lightly anesthetized dog (4) and in man (5) by means of cardiac cathet,erization have confirmed and extended the previous work. There has been, however, no systematic study of lactate and pyruvate metabolism in cardiac muscle slices, although there have been a few isolated observations of the effect of thesct substrates upon respiration in slices (&IO) and homogenates (11). III view of the interest in this laboratory in studying t.he effect of vitamin deficiencies upon cardiac metabolism (12-14) in vitro, it was thought important to document the effect of certain variables upon the utilization of pyruvatc and lactate in normal heart slices. Later studies in this laboratory have dealt with the synthesis of radioactive L(+)and D(-)lactic acids, as well as with the metabolism of thcsc isomers in animal tissues (15). The present paper is devoted to a study by the Warburg technique of the mct,abolism of pyruvatc and m-lactate in slices of heart ventricle