D-glucose Stimulates the Na+/K+
Pump in Mouse Pancreatic Islet Cells |
| |
Authors: | Adrian Elmi Lars-?Ke Idahl Per-Erik Sandstr?m Janove Sehlin |
| |
Affiliation: | 1. Department of Integrative Medical Biology, Section for Histology and Cell Biology, Umed University, Umed, SE-901 87, Sweden, |
| |
Abstract: | To determine the effect of D-glucose on the β-cellNa+/K+ pump, 86Rb+ influx was studied in isolated,-cell-rich islets of Umeå-ob/ob mice in the absenceor presence of lmM ouabain. D-glucose (20 mM)stimulated the ouabain-sensitive portion of 86Rb+influx by 65%, whereas the ouabain-resistantportion was inhibited by 48%. The Na+/K+ ATPaseactivity in homogenates of islets of Umeå-ob/obmice or normal mice was determined to search fordirect effects of D-glucose. Thus, ouabain-sensitiveATP hydrolysis in islet homogenates was measuredin the presence of different D-glucose concentrations.No effect of D-glucose (3–20 mM)was observed in either ob/ob or normal islets atthe optimal Na+/K+ ratio for the enzyme (135 mMNa+ 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 atoptimal Na+/K+ ratio, whereas 50 μM of the drughad no effect. The results suggest that D-glucoseinduces a net stimulation the Na+/K+ pump of β-cells in intact islets and that D-glucose doesnot exert any direct effect on the Na+/K+ ATPase activity. |
| |
Keywords: | |
|
|