Effect of epinephrine on glycogen stores

Abstract

Subcutaneous epinephrine doses of 0.1 mg/kg or more consistently produced declines in muscle glycogen of rats. Transient declines (30%) in liver glycogen, followed by net resynthesis to levels above the control value, were observed after subcutaneous doses 0.2–0.4 mg/kg. Subcutaneous doses of 6.0 mg/kg were required to produce progressive depletion of liver glycogen (82%), over a 3-hour period. However, such depletion was uniformly obtained by intraperitoneal injection of much smaller doses (0.4 mg/kg/hr.). High blood levels of lactate and glucose did not reverse glycogenolysis in liver or in muscle when adequate concentrations of epinephrine were maintained. Although intraperitoneal injection of epinephrine leads to high concentrations at the liver and lower concentrations at skeletal muscle, intraperitoneal doses of 0.1 mg/kg/hr. produced declines in muscle glycogen but not in liver glycogen. It is concluded that the concentration of epinephrine required to produce glycogenolysis in the liver is at least 5–10 times as high as that effective in the muscle. The transient hepatic glycogenolysis observed after relatively small subcutaneous doses of epinephrine may be due to stimulation of endogenous glucagon release.