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International Journal of Experimental Diabetes Research
Volume 1 (2000), Issue 2, Pages 155-164
http://dx.doi.org/10.1155/EDR.2000.155

D-glucose Stimulates the Na+/k+ Pump in Mouse Pancreatic Islet Cells

Department of Integrative Medical Biology, Section for Histology and Cell Biology, Umed University, Umed SE-901 87, Sweden

Received 30 December 1999; Accepted 12 February 2000

Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

To determine the effect of D-glucose on the β-cell Na+/k+ pump, R86b+ influx was studied in isolated, -cell-rich islets of Umeå-ob/ob mice in the absence or presence of lmM ouabain. D-glucose (20 mM) stimulated the ouabain-sensitive portion of R86b+ influx by 65%, whereas the ouabain-resistant portion was inhibited by 48%. The Na+/k+ ATPase activity in homogenates of islets of Umeå-ob/ob mice or normal mice was determined to search for direct effects of D-glucose. Thus, ouabain-sensitive ATP hydrolysis in islet homogenates was measured in the presence of different D-glucose concentrations. No effect of D-glucose (3–20 mM) was observed in either ob/ob or normal islets at the optimal Na+/k+ ratio for the enzyme (135 mM Na+ and 20 mM K+). Neither D-glucose (3–20 mM) nor L-glucose or 3-O-methyl-D-glucose (20 mM) affected the enzyme activity at a high Na+/k+ ratio (175 mM Na+ and 0.7mM k+). Diphenylhydantoin (150 μM) decreased the enzyme activity at optimal Na+/k+ ratio, whereas 50 μM of the drug had no effect. The results suggest that D-glucose induces a net stimulation the Na+/k+ pump of β-cells in intact islets and that D-glucose does not exert any direct effect on the Na+/k+ ATPase activity.