DPN-LINKED CYTOPLASMIC METABOLITES IN THE RAT-LEG MUSCLE, IN SITU, DURING CONTRACTION AND RECOVERY.
Rept. for Jul 63-Dec 64,
CHEMICAL RESEARCH AND DEVELOPMENT LABS EDGEWOOD ARSENAL MD
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The role of various metabolic pathways for mediating the oxidation of extramitochondrial reduced diphosphopyridine nucleotide DPNH in vivo as a function of physiological activity of leg muscle of the rat was explored. The following conclusions were reached The DPN-linked cytoplasmic metabolites, lactate, alphaglycerophosphate alpha-GP, and malate, accumulate linearly during the first 100 contractions of rat-leg muscle in situ. The oxidized redox intermediate, pyruvate, also accumulates, whereas the concentrations in muscle of dihydroxyacetonephosphate DHAP and oxaloacetate do not change. The increase in concentration of pyruvate corresponds to that of alpha-GP, suggesting that the transfer of hydrogen from DPNH to DHAP to form alphaGP enables pyruvate to accumulate. During the initial period of exercise, the ratio of lactate to pyruvate remains constant while that of alpha-GP to DHAP increases severalfold. With prolonged exercise, lactate and malate continue to accumulate, whereas pyruvate and alpha-GP reach a maximal titer after about 100 contractions and then decrease. During recovery after stimulation, the levels of the accumulated metabolites return to prestimulatory levels at independent rates. Author