Effect of hypothermia on the insulin-receptor interaction in adipose plasma membranes.

The aim of the study was to compare the number and affinity of insulin receptors in adipose tissue of both normothermic and hypothermic rats. Plasma membranes from epididymal adipose tissue were prepared and purified according to Havrankowa and binding assay was performed using (125I)-iodoinsulin. The kinetic parameters of the hormone-receptor interaction were analysed by the method of Scatchard using the LIGAND--Pc v.3.1. computer program of Munson and Rodbard. The binding potency of insulin was calculated as IC50 using the ALLFIT--Pc v. 2.7. computer program. Maximum specific insulin binding to plasma membranes in adipose tissue was decreased in the hypothermic rats but half-maximum displacement of tracer insulin was similar in the normothermic and hypothermic group suggesting that reduced receptor numbers rather than reduced affinity accounted for the difference.