Heterogeneity of glycogen synthesis upon refeeding following starvation
1992
Calder, P.C. | Geddes, R.
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 micromoles/g tissue to 16 micromoles/g tissue) and 55% (from 40 micromoles/g tissue to 18.5 micromoles/g tissue), respectively. 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 alpha-glucosidase activity increased 1.8-fold following starvation. 3. Refeeding resulted in liver glycogen synthesis at a linear rate of 40 micromoles/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 (approximately 670 micromoles/g tissue). 4. Refeeding resulted in skeletal muscle glycogen synthesis at an initial rate of 40 micromoles/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 (approximately 50 micromoles/g tissue). 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.
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