Direct Control of Glycogen Metabolism in the Perfused Rat Liver by the Sympathetic Innervation

Abstract

The mode of action of hepatic nerves on the metabolism of carbohydrates was studied in the rat liver perfused in situ. Electrial stimulation of the nerve bundles around the hepatic artery and the portal vein resulted in an increase of glucose and lactate output, an enhancement of phosphorylase a activity and a decrease of portal flow. Sodium nitroprusside prevented the hemodynamic changes after nerve stimulation without affecting the metabolic alterations. Phentolamine or an extracellular Ca level below 300 .mu.mol .times. 1-1 abolished both hemodynamic and metabolic changes after nerve stimulation, while propranolol or atropine were without effect. Norepinephrine infusion mimicked nerve stimulation only at the highly unphysiological concentration 0.1 .mu.M; it was not effective at a concentration of 0.01 .mu.M, which might be reached in the sinusoidal blood due to an overflow from intrahepatic synapses. In rat liver, glycogen breakdown apparently is regulated by .alpha.-sympathetic nerves directly rather than indirectly via hemodynamic changes or via norepinephrine overflow.