The effects of streptozotocin-induced diabetes and of insulin supplementation to diabetic rats on glycogen-metabolizing enzymes in liver were determined. The results were compared with those from control animals. The activities of glycogenolytic enzymes, i.e. phosphorylase (both a and b), phosphorylase kinase and protein kinase (in the presence or in the absence of cyclic AMP), were significant...

The glycogenolytic-sarcoplasmic reticulum complex from rat skeletal muscle accumulates Ca2+ upon stimulation of glycogen phosphorolysis in the absence of added ATP. It is shown that an efficient Ca2+ uptake involves the sequential action of glycogen phosphorylase, phosphoglucomutase and hexokinase, which generate low concentrations of ATP (approximately 1-2 microM) compartmentalized in the imme...

The objective was to study the regulation of glycogenolytic enzyme mRNAs in porcine satellite cells during proliferation and differentiation. Beyond 80% confluence, cells were grown in absence or presence of 1μM insulin. The observed increases in abundance of mRNA for glycogenin, glycogen synthase, phosphorylase kinase, phosphorylase and glycogen debranching enzyme, and no alterations of the tr...

The livers removed from thyroidectomized and L-T4 supplemented rats were rapidly frozen by Freon-12 chilled with liquid nitrogen, and concentrations of metabolites which affect glycogen synthetase and phosphorylase were determined. Serum and liver glycose levels were not changed in any thyroid functioning. But liver G6P and ATP were increased by thyroidectomy and decreased by L-T4 supplement, w...

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 experiment...

Calorimetric titrations of glycogen phosphorylase b (EC 2.4.1.1) from rabbit muscle with its allosteric activator, AMP, have been carried out at 25 “C and pH 6.9 in three different buffer systems (glycylglycine, glycerophosphate, and tris(hydroxymethy1)aminomethane). Calorimetric curves of biphasic nature were originally obtained. This biphasic behavior was always concomitant with: (a) a depen...

Glycogen plays a major role in supporting the energy demands of skeletal muscles during high intensity exercise. Despite its importance, the amount of glycogen stored in skeletal muscles is so small that a large fraction of it can be depleted in response to a single bout of high intensity exercise. For this reason, it is generally recommended to ingest food after exercise to replenish rapidly m...