Glucose-induced [Ca2+]i oscillations in single human pancreatic islets.
Changes in cytosolic free calcium concentrations ([Ca2+]i) in response to stimulatory glucose concentrations were investigated in human pancreatic islets, using Fura-2 fluorescence imaging. Increasing glucose concentration from 3 to 11 mM caused a triphasic [Ca2+]i response in human islets: an initial decrease (phase 1), a rapid and transient increase (phase 2) and periodic oscillations with a frequency of 1 +/- 0.3 min-1 (phase 3). Raising the glucose concentration from 11 to 16.7 mM lowered the frequency of the glucose-induced [Ca2+]i oscillations to 0.15 +/- 0.2 min-1, without changes in their amplitude. Human islet [Ca2+]i response to stimulatory glucose concentrations is synchronous throughout the islet. Freshly isolated human islets responded to tolbutamide (50 microM) with a rise in [Ca2+]i. An increase in glucose concentration, from 3 to 16 mM, in the presence of 100 microM diazoxide, produced a decrease in [Ca2+]i. It is concluded that human islets respond to glucose with regular [Ca2+]i oscillations that are synchronous throughout the islet and whose duration is modulated by glucose.
Martín
F
F
Department of Physiology, School of Medicine, University of Alicante, Spain.
Soria
B
B
D000230:Adenocarcinoma; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003981:Diazoxide / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D010190:Pancreatic Neoplasms; D010195:Pancreatitis; D015221:Potassium Channels / Q000502:physiology; D014044:Tolbutamide / Q000494:pharmacology
D005456:Fluorescent Dyes; D007004:Hypoglycemic Agents; D015221:Potassium Channels; D014044:Tolbutamide; D005947:Glucose; D003981:Diazoxide; D002118:Calcium; D016257:Fura-2