Abstract
Fructose and glucose, when administered as a single, large intravenous dose (500 mg/kg) produced opposite effects on key regulatory enzymes of glycogen metabolism in intact normal fed animals. Glucose rapidly stimulated glycogen synthase phosphatase activity and increased the proportion of glycogen synthase in the active (I) form as expected; fructose reduced synthase phosphatase activity and the proportion of synthase in the I form. Glucose also stimulated a reduction in the proportion of phosphorylase in the active (a) form, whereas fructose stimulated an increase in the proportion of phosphorylase in the a form. The effect of fructose was not mediated by an increase in cyclic adenylate (cAMP) concentration nor by a conversion of phosphorylase kinase b to phosphorylase kinase a. As expected, the concentration of ATP decreased significantly. The increase in proportion of phosphorylase in the a form may be due to stimulation of phosphorylase kinase b activity by a decrease in the intracellular ATP:Mg++ ratio or by an increase in intracellular Ca++ concentration. The mechanism of the fructose-induced change in synthase phosphatase activity and in synthase I activity is unknown.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 965-969 |
| Number of pages | 5 |
| Journal | Metabolism: clinical and experimental |
| Volume | 29 |
| Issue number | 10 |
| DOIs | |
| State | Published - 1980 |
Bibliographical note
Funding Information:From the Endocrine-Metabolic Section, Veterans Administration Medical Center, Minneapolis. Mnn. and the Departments of Medicine and Biochemistry, University of Minnesota. Mtnneapolis, Minn. Received for publication December 28. 1979. Supported by Veterans Administration Research Funds and the American Diabetes Association, Mnnesota Afil-iate. Address reprint requests Frank Q. Nuttall, M.D., Ph.D., Veterans Administration Medical Center, 54th Street and 48th Avenue South, Minneapolis. Minn. 55417. 8 1980 by Grune & Stratton, Inc. 00260495/80/291~10%01.00/0