Phosphorylation of a Fat-Cell Protein: Effect of Starving and Re-feeding WILLIAM B. BENJAMIN, SUSAN T. FISH and IRWIN SINGER

1951) showed that fructose metabolism was unaffected by the diabetic condition whereas that of glucose was altered. Fructose has been shown to lower ATP concentrations and those of cyclic AMP, increased previously by glucagon, and decrease phosphorylase ‘a’ in the liver of normal mice (van den Berghe et al., 1973). These effects of fructose could partly account for the results of our experiments, since it is known that diabetic animals have increased hepatic cyclic AMP concentrations (Das, 1973) and thus possibly increased phosphorylase activity, as well as having a lower percentage of glycogen synthetase in the ‘a’ form (Steiner et al., 1961). However, as the addition of fructose, with glucose, to the perfusion medium did not produce significant glycogen accumulation, it appears that the hexoses must be acting together with other factors during pretreatment of diabetic rats, to produce the eventual changes (during perfusion) in the enzymes concerned with glycogen metabolism.