Heterogeneity of glycogen synthesis upon refeeding following starvation

Abstract

1. 1. Starvation of rats for 40 hr decreased the body weight, liver weight and blood glucose concentration. The hepatic and skeletal muscle glycogen concentrations were decreased by 95% (from 410 μmol/g tissue to 16 μmol/g tissue) and 55% (from 40 μmol/g tissue to 18.5 μmol/g tissue), respectively. 2. 2. Fine structural analysis of glycogen purified from the liver and skeletal muscle of starved rats suggested that the glycogenolysis included a lysosomal component, in addition to the conventional phosphorolytic pathway. In support of this the hepatic acid α-glucosidase activity increased 1.8-fold following starvation. 3. 3. Refeeding resulted in liver glycogen synthesis at a linear rate of 40 μmol/g tissue per hr over the first 13 hr of refeeding. The hepatic glycogen store was replenished by 8 hr of refeeding, but synthesis continued and the hepatic glycogen content peaked at 24 hr (∼670 μmol/g tissue). 4. 4. Refeeding resulted in skeletal muscle glycogen synthesis at an initial rate of 40 μmol/g tissue per hr. The muscle glycogen store was replenished by 30 min of refeeding, but synthesis continued and the glycogen content peaked at 13 hr (∼50 μmol/g tissue). 5. 5. Both liver and skeletal muscle glycogen synthesis were inhomogeneous with respect to molecular size; high molecular weight glycogen was initially synthesised at a faster rate than low molecular weight glycogen. These observations support suggestions that there is more than a single site of glycogen synthesis. © 1991.