Insulin secretion by the perfused pancreas of the cold-acclimated rat.

Rats were acclimated to cold at 4 degrees C for a period of 42 days. Pancreases of normal and cold-acclimated rats were isolated and perfused with a Krebs-Henseleit bicarbonate medium containing dextran, adenosine, glucose, and a fluorocarbon as oxygen carrier. The biphasic secretion pattern of insulin in response to glucose stimulation was evident in both groups. Both basal and glucose-induced insulin release from pancreases of cold-acclimated rats exhibited a very significant reduction in comparison with controls (p less than 0.001). These observations are interpreted as indicating that cold-acclimation, an altered steady state of metabolism, is characterized by enhanced sympathetic activity which reduces insulin availability and release. Consequently enhanced free fatty acid mobilization resulting from reduced inhibition by insulin of lipolysis in the peripheral fat depots and increased lipolysis resulting from sympathetic activation are seen.