Effects of cations, ionophores and hypoglycemic sulfonylureas on the fluorescence of fluorescein-labelled pancreatic islets.
The stimulation of Ca2+ inflow into pancreatic islet cells resulting from either an increase in extracellular K+ (from 5 to 37 mM) or Ca2+ (from 1 to 20 mM) concentration or the administration of tolbutamide, glibenclamide and the ionophores A23187 or X537A resulted in an apparent fall of cellular pH as judged from the fluorescence of islets prelabelled with fluorescein diacetate. In all cases, the decrease in pH was abolished when the experiments were repeated in the absence of extracellular Ca2+. These results suggest that the cytosolic concentration of Ca2+ may affect the pH of islet cells, possibly by displacing H+ from intracellular binding sites.
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D005452:Fluoresceins; D005453:Fluorescence; D005905:Glyburide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D007832:Lasalocid / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D014044:Tolbutamide / Q000494:pharmacology
D005452:Fluoresceins; D007004:Hypoglycemic Agents; D000001:Calcimycin; D014044:Tolbutamide; D011188:Potassium; D005905:Glyburide; D002118:Calcium; D007832:Lasalocid