BETA(3)-ADRENERGIC ACTIVATION OF ADENYLYL-CYCLASE IN MOUSE WHITE ADIPOCYTES - MODULATION BY GTP AND EFFECT OF OBESITY

Lipolysis and adenylyl cyclase (AC) activation in response to beta-adr energic agents are abnormally low in white epididymal adipose tissue ( WAT) of the ob/ob mouse. The abundance of C-proteins (G(5) alpha and G (i) alpha) linked to AC is also abnormally low. By contrast, beta-adre nergic receptor (beta-AR) levels were previously found to be normal in WAT and elevated in liver. The relative importance of various forms o f the beta-AR in mouse WAT was reassessed in view of the discovery of the beta(3)-AR. The results show that (1) the beta(3)-AR is mainly res ponsible for AC activation in lean-mouse WAT; (2) the beta(3)-AR is on ly partly responsible for AC activation in obese mouse WAT; and (3) CT P modulates beta(3)-but not beta(1)-or beta(2)-AR activation of AC in a biphasic manner. Therefore, the beta(3)-AR appears responsible for t he well-known bimodal effect of GTP on beta-adrenergic receptor-mediat ed AC activity in WAT. (C) 1995 Wiley-Liss, Inc.