D-glucose stimulates the Na+/K+ pump in mouse pancreatic islet cells.
To determine the effect of D-glucose on the beta-cell Na+/K+ pump, 86Rb+ influx was studied in isolated, -cell-rich islets of Umeå-ob/ob mice in the absence or presence of 1mM ouabain. D-glucose (20mM) stimulated the ouabain-sensitive portion of 86Rb+ 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 (3-20mM) was observed in either ob/ob or normal islets at the optimal Na+/K+ ratio for the enzyme (135mM Na+ and 20mM K+). Neither D-glucose (3-20mM) nor L-glucose or 3-O-methyl-D-glucose (20mM) affected the enzyme activity at a high Na+/K+ ratio (175 mM Na+ and 0.7 mM K+). Diphenylhydantoin (150 microM) decreased the enzyme activity at optimal Na+/K+ ratio, whereas 50 microM of the drug had no effect. The results suggest that D-glucose induces a net stimulation the Na+/K+ pump of beta-cells in intact islets and that D-glucose does not exert any direct effect on the Na+/K+ ATPase activity.
Elmi
A
A
Department of Integrative Medical Biology, Section for Histology and Cell Biology, Umeå University, Sweden.
Idahl
L A
LA
Sandström
P E
PE
Sehlin
J
J
D019325:3-O-Methylglucose / Q000494:pharmacology; D000818:Animals; D005260:Female; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008820:Mice, Obese; D009765:Obesity / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology; D012016:Reference Values; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*; D013237:Stereoisomerism
D019325:3-O-Methylglucose; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D005947:Glucose; D012413:Rubidium