EFFECT OF HYPOTHERMIA ON SKELETAL-MUSCLE METABOLISM IN PERFUSED RAT HINDLIMB

Temperature-induced metabolic change was studied with isolated rat hin dlimb muscle to elucidate how tissue viability is maintained under hyp othermia. The hindlimb was perfused with Krebs-bicarbonate buffer cont aining 4% (w/v) polyvinylpyrrolidone (PVP-40T) in a flowthrough mode a l 35-8 degrees C. when the temperature was lowered, the following resu lts were observed: (i) Vascular resistance (defined as perfusion press ure divided by how rate) increased proportionally with elevation of th e viscosity of the perfused medium, suggesting that the capillary bed in the perfused muscle is maintained under a similar condition under t hese temperatures; (ii) the Arrhenius plot of the O-2 uptake rate show ed a break at ca. 20 degrees C, where the activation energy between 20 and 8 degrees C was ca. 3.5 times higher than that between 35 and 20 degrees C; (iii) the rates of O-2 uptake and lactate release decreased , but the lactate/ pyruvate ratio increased even under aerobic conditi ons; (iv) oxygenation of myoglobin and oxidation of cytochromes increa sed, suggesting a reduced electron-transfer rate in spite of improved or sufficient oxygenation of the tissue. Based on these results, we co ncluded that oxidative phosphorylation is more affected by temperature than glycolysis, and thus under hypothermia, the role of glycolysis i n energy production increases in rat skeletal muscle, especially below 20 degrees C. (C) 1996 Academic Press, Inc.