On the regulation of glycogen metabolism in Tetrahymena

Abstract

The glycogen phosphorylase and glycogen synthetase activities of Tetrahymena pyriformis were assayed after growth of cells under various conditions. Cells exposed to low concentrations of theophylline or to low oxygen tension during growth in proteose-peptone medium had increased synthetase and phosphorylase activities. Supplementing the medium with glucose increased the synthetase activity. Growth in the presence of both glucose and theophylline markedly increased the synthetase activity and decreased the phosphorylase activity. Neither reserpine nor dichloroisoproterenol affected the synthetase activity, but either or both drugs increased the phosphorylase activity. Triiodothyronine did not affect the phosphorylase activity but inhibited the synthetase activity. It was also found that Tetrahymena had 3′,5′-cyclic AMP phosphodiesterase activity and that caffeine and theophylline inhibited this activity. The effects of glucose supplementation, low oxygen tension, and of the drugs mentioned above were correlated with their effects on cell glycogen content, and the implications of these findings with respect to the control of glycogen metabolism are discussed.