Abstract
CORTISONE is reported to increase glycogen storage in rabbit muscle and inhibit the activity of the enzyme phosphorylase which catalyzes reversibly the conversion of glucose-1-phosphate to glycogen (1). Epinephrine increases or maintains this enzyme activity, depending on conditions, in the isolated rat diaphragm (2). In an attempt to elucidate some unexplained interactions of these hormones in regulating muscle glycogen storage (3, 4), the following study was made on the effect of these hormones on phosphorylase activity in rat skeletal muscle.