Na+ participates in loop diuretic-sensitive Cl(-)-cation co-transport in the pancreatic beta-cells.
In order to investigate whether Na+ participates in loop diuretic-sensitive Cl(-)-cation co-transport in the beta-cells, we tested the interaction between the effects of Na+ deficiency, furosemide and D-glucose on 86Rb+ fluxes in beta-cell-rich mouse pancreatic islets. Removal of extracellular Na+ slightly reduced the ouabain-resistant 86Rb+ influx and the specific effect of 1 mM furosemide on this influx was significantly smaller in Na(+)-deficient medium. The capacity of 20 mM D-glucose to reduce the ouabain-resistant 86Rb+ influx was not changed by removal of extracellular Na+. The 86Rb+ efflux from preloaded islets was rapidly and reversibly reduced by Na+ deficiency. Furosemide (1 mM) reduced the 86Rb+ efflux and the effect of the combination of Na+ deficiency and 1 mM furosemide was not stronger than the effect of furosemide alone. 22Na+ efflux was reduced by both ouabain and furosemide and the effects appeared to be additive. The data suggest that Na+ participates in loop diuretic-sensitive Cl(-)-cation co-transport in the pancreatic beta-cells. This adds further support to the idea that beta-cells exhibit a Na+, K+, Cl- co-transport system. Since some of the furosemide effect on 86Rb+ efflux persisted in the Na(+)-deficient medium, it is likely that also loop diuretic-sensitive K+, Cl- co-transport exists in this cell type.
Department of Histology and Cell Biology, University of Umeå, Sweden.
P E
PE
Sandström
J
J
Sehlin
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002412:Cations; D002712:Chlorides / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008820:Mice, Obese; D010042:Ouabain / Q000494:pharmacology; D012414:Rubidium Radioisotopes / Q000378:metabolism; D012964:Sodium / Q000502:physiology*; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D002412:Cations; D002712:Chlorides; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D005947:Glucose