Calorigenic effects of noradrenaline and glucagon on white adipocytes in cold- and heat-acclimated rats

Calorigenic actions of noradrenaline and glucagon on isolated epididymal fat cells from warmacclimated controls, cold-acclimated and heatacclimated rats were measured by the use of a twin-type conduction microcalorimeter. Both noradrenaline and glucagon stimulated heat production in isolated adipocytes maximally in doses of 1 g/ml and 10g/ml, respectively. Maximal responsiveness of adipocytes per unit cell to noradrenaline was not influenced by cold acclimation, while it was reduced by heat acclimation. Maximal response in total epididymal fat cells to noradrenaline was increased in cold acclimation and not changed in heat acclimation at increased numbers of adipocytes in both cold-acclimated and heatacclimated animals. Maximal response per unit cell as well as per total epididymal fat cells to glucagon was increased in cold acclimation and reduced in heat acclimation.The present results indicate that the modified responses of target adipocytes to noradrenaline and glucagon are involved in the development of temperature acclimation.