Glucose-6-phosphatase activity in normal and denervated developing chick gastrocnemii: reappraisal of glycogenolytic and glycolytic metabolism in skeletal muscle

Abstract

Biochemical changes in glycogen content and activity levels of phosphorylase (EC 2.4.1.1), glucose-6-phosphatase (EC 3.1.3.9), phosphohexose isomerase (EC 5.3.1.9) and aldolase (EC 4.1.2.13) have been studied in normal and denervated whole gastrocnemius muscle and its three fasciculi, viz., pars externus, medius and internus up to 9 weeks in chicks. Glycogen content as well as phosphorylase, phosphohexose isomerase and aldolase decrease in normal muscle with advancement of postembryonic growth whereas transiently increased glucose-6-phosphatase reveals an inverse relationship with these parameters. Denervated muscles demonstrate loss of glycogen and related enzymes owing to ablation of neural supply during the initial 4 weeks. Denervation results in a delayed stimulation of glycogenolysis and glycolysis which seems to be governed by decreasing activity of glucose-6-phosphatase. The significance of glucose-6-phosphatase in the regulation of glycogenolysis and glycolytic metabolism of normal and denervated skeletal muscle is discussed.