Major metabolic pathways for carbohydrate metabolism of voluntary skeletal muscle

Abstract

When muscle fiber groups from the rhesus monkey (Macaca mulatta) were incubated under aerobic conditions, 50% of the label from the glucose uptake was accounted for by lactate-C14, 5% by pyruvate-C14, 6% by C14O2, and 16% by glycogen-C14 production. The percents of label from glucose uptake appearing in the various fractions (specific yields X 102) were the same for glucose I- and glucose 6-C14. Under anaerobic conditions, the glucose uptake doubled and the percent of label from glucose uptake appearing in lactate increased, whereas the percent in pyruvate, glycogen, and CO7 decreased. The specific yields of lactate, pyruvate, and glycogen were the same for glucose I- and glucose 6-C14. The specific yield of C14O2 from glucose I-C14 was four times greater than that from glucose 6-C14. However, less than 0.5% of the glucose uptake was metabolized via the pentose cycle. Incubation of muscle fiber groups in medium containing 20 m[image] pyruvate had no effect on glucose uptake, lactate production, or glycogen concentration. The ratio of 1.4 for the specific yields of C14O2 from glucose I-and glucose 6-C14 indicated the presence of pentose cycle activity. However, in the presence of a high level of pyruvate in the medium, pentose cycle activity was insignificant in relation to the total amount of glucose metabolized.