Ethanol inhibition of insulin secretion by perifused rat islets

In vivo and in vitro effects of ethanol on the kinetics of insulin secretion in response to glucose and tolbutamide were studied in perifused rat islets. Phases I and II insulin response to 16.7 mM glucose was decreased 46% and 48%, respectively, in islets of rats given ethanol intragastrically 1 g/kg 1 h prior to sacrifice. Mean blood ethanol levels at the time of animal sacrifice were 19.4 mmol/l. The magnitude of insulin suppression was not significantly enhanced with higher ethanol doses, 2 or 3 g/kg, although mean blood ethanol levels increased to 25.9 and 60.3 mmol/l, respectively. Similarly, significant inhibition of both phases of insulin response to glucose occurred when ethanol 1 or 3 g/kg was given intraperitoneally instead of orally. Ethanol had no effect on insulin secretion when given orally 4 h instead of 1 h prior to islet isolation. Ethanol, 65 mmol/l, added directly to rat islets perifusate simultaneously with 16.7 mM glucose decreased both phases I and II insulin response nearly half; whereas addition of 21.7 instead of 65 mmol/l ethanol had no effect. Pre-treatment of islets with 21.7 or 65 mmol/l ethanol during 30 min basal islets perifusion period had no effect on subsequent insulin response to 16.7 mM glucose. Insulin response to 10 mM tolbutamide was decreased nearly 81% by the simultaneous presence of 65 mmol/l ethanol in islets perifusate.