Effect of Hyperthyroidism on Glycogen Content of the Isolated Rat Liver

Abstract

A method is described for determining net changes in glycogen content of the isolated rat liver after 6 hours of perfusion using the glycogen content of the caudate lobe of the liver as a control value. A series of experiments was performed in which livers obtained from normal and hyperthyroid rats were perfused at low and high perfusate glucose levels and the glycogen content of the livers was determined before and after perfusion. It was found that the isolated liver from the untreated rat under artificial perfusion neither increases nor decreases appreciably in glycogen concentration during a period of six hours at either low or high glucose perfusate concentrations. In contrast, the isolated hyperthyroid rat liver, which is uniformly low in glycogen concentration, effects a marked increase in its glycogen concentration by the end of perfusion at high perfusate glucose concentration (above 600 mg.%). It was concluded that the data confirm the effect of thyroxine in depleting the liver of its glycogen content, and establishes that thyroxine-influences the metabolism of the hyperthyroid liver and its enzyme systems in promoting glycogen storage even in the presence of increased glucose metabolism.