Abstract
The changes in levels of glycolytic intermediates of leg muscles were studied in vivo on 4 groups of rats: the conrol, the insulin-administered, the streptozotocin-diabetic, and the insulinadministered diabetic group. Activities of some glycolytic enzymes in the muscles of the 4 groups were assayed.
1) In the diabetic group without the electrical stimulation, levels of glycogen and lactate were increased about 1.5-fold, but those of other glycolytic intermediates were not changed. Activities of phosphofructokinase, pyruvate kinase, and lactate dehydrogenase were not affected by inducing diabetes, but the pyruvate dehydrogenase complex was decreased. Activities of the pyruvate dehydrogenase complex were restored by insulin administration.
2) In both insulin-administered groups, levels of glycolytic intermediates (except the increase in glucose 1-phosphate, glucose 6-phosphate and lactate) were unchanged. Activities of key enzymes in glycolysis also remained constant.
3) In all of the 4 groups, the electrical stimulation resulted in a decrease in the glycogen level and the increase in levels of some glycolytic intermediates. There was no difference among the groups in metabolic changes by the electrical stimulation.
It is concluded that the metabolic steps from glucose 6-phosphate to pyruvate in the skeletal muscle of the diabetic rat is not affected, but the step catalyzed by the pyruvate dehydrogenase complex is supressed, and that the enhancement of glycolysis by insulin administration is not accompanied by an increase in the quantities of glycolytic key enzymes.
