The metabolism of lactate.

Lactate contents of tissues can vary during normal physiological conditions in mammals from 0.5 to over 5 mM, and higher in pathological states, suitable for measurement by NMR. Lactate itself is a dead-end metabolite, metabolized only by lactate dehydrogenase. The extent and direction of that reaction is determined by the free [NAD+]/[NADH][H+] ratio of cytoplasm with which lactate and pyruvate are in near-equilibrium. Pyruvate is a crossroads of most of the major degradative and synthetic pathways, but present in about one-tenth the amount of lactate. Information on the content of both lactate and its redox partner pyruvate is likely to provide more information on the metabolic state of tissue than are measurements of lactate alone.