NEURAL CONTROL OF ADENYLATE-CYCLASE RESPONSIVENESS IN BROWN ADIPOSE-TISSUE

Abstract

The effects of cold exposure on sympathetic nerve activity in interscapular brown adipose tissue (IBAT) and the impact of those changes on the responsiveness of the adenylate cyclase system were investigated. Exposing rats of 4.degree. C for 3 days increased norepinephrine turnover in IBAT and increased the ability of norepinephrine to stimulate adenylate cyclase activity. This 2- to 3-fold increase in adenylate cyclase activity appeared to result from increased nerve transmission because it was abolished by prior surgical denervation of IBAT. Cold exposure did not affect the number of .beta.-adrenergic receptors in IBAT. Cold exposure increased the maximal response of adenylate cyclase to fluoride and guanosine-5''-(.beta.,.gamma.-imino)triphosphate stimulation by 2-3-fold. Increased nerve transmission produces supersensitivity of IBAT adenylate cyclase and this effect is mediated by a postreceptor modification of the adenylate cyclase system.