Response of muscle glycogen and phosphorylase to electrical stimulation in trained and nontrained guinea pigs

Abstract

Total phosphorylase activity determined histochemically was selectively depleted in white fibers of the medial gastrocnemius of adult guinea pigs after 1 hour of electrical stimulation at a frequency of 5/sec. Histochemical depletion of phosphorylase was paralleled by glycogen depletion measured spectrophotometrically in homogenates and histochemically in frozen sections. Every phosphorylase-negative fiber was negative for glycogen as determined by the PAS stain. The number of PAS-negative fibers slightly exceeded the number of phosphorylase-negative fibers. No PAS- and 11 phosphorylase-negative fibers were found in nonstimulated muscles. The histochemical depletion of glycogen and of phosphorylase was more pronounced in the nontrained than in the trained animals.