Lactate and pyruvate kinetics in isolated perfused rat hearts.

HENDERSON, ANDREW H., ROBERT J. CRAIG, RICHARD GORLIN, AND EDMUND Iif. SONNENBLKK. Lactate and fyruvate kinetics in Z’SOla&perfused rat hearts. Am. J, Physiol. 2 17 (6) : 1752-I 756. 1969.Myocardial lactate and pyruvate kinetics have been studied by measuring their concentrations in arterial, venous, and tissue samples from isolated rat hearts perfused with different concentrations of single substrates. The relative efflux rates of pyruvate were found to be 10 times greater than those of lactate, An approximately direct relationship between arterial and tissue concentrations of lactate resulted from perfusing with different concentrations of lactate; however there was a point of equilibrium between the lowest arterial concentrations where net efflux of lactate occurred, and higher concentrations where net influx occurred. Insofar as lactate is almost completely ionized at physiological pH, the intracellular concentrations of lactate at this point of equilibrium and during net influx appeared to be higher than would have been predicted on the basis of pasive diffusion. Compartmentalization of lactate within the cell is postulated as the most likely explanation for these findings, taken together.