Stimulus-secretion coupling of glucose-induced insulin release. XXIX. Regulation of 86Rb+ efflux from perfused islets.
Glucose provokes a dose-related, rapid, sustained, and rapidly reversible reduction in the fractional outflow rate of 86Rb+ from perfused pancreatic islets. This efflux probably corresponds to a passive movement driven by the electrochemical gradient of K+ across the plasma membrane and mediated by a native ionphoretic system. Indeed, it is facilitated by valinomycin or cell membrane depolarization, little affected by ouabain, and inhibited by verapamil or omission of extracellular K+. The effect of glucose upon 86Rb+ efflux does not appear to be directly attributable to changes in either glucose transport, plasma cell polarization, Na+ influx, cyclic AMP concentration, or insulin secretion. Although a modulatory role of intracellular Ca2+ on K+ conductance cannot be ruled out, the experimental data suggest rather that the glucose-induced modification of 86Rb+ fractional outflow rate is directly linked, for its major part, to metabolic events such as an increase in the rate of glycolysis and/or generation of reduced pyridine nucleotides.
D000818:Animals; D001464:Barium / Q000378:metabolism; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000494:pharmacology*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D010477:Perfusion; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012413:Rubidium / Q000378:metabolism*; D014044:Tolbutamide / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
D007328:Insulin; D014634:Valinomycin; D001464:Barium; D010042:Ouabain; D014701:Veratridine; D014044:Tolbutamide; D014700:Verapamil; D008274:Magnesium; D005947:Glucose; D012413:Rubidium; D011188:Potassium; D002118:Calcium