Effects of salbutamol and butoxamine on the human fat cell adenylate cyclase.

In order to characterize the beta-adrenoceptors coupled to the human fat cell adenylate cyclase more extensively the effects of the beta 2-selective agonist salbutamol on basal and isoproterenol-stimulated rates of cAMP-accumulation were studied. Although exhibiting only low intrinsic activity salbutamol displayed only slightly lower affinity towards the beta-adrenoceptors linked to the human fat cell adenylate cyclase than isoproterenol. In addition, the beta 2-selective antagonist butoxamine was slightly more potent in inhibiting the isoproterenol-stimulated fat cell enzyme than the cardioselective beta-blocking agent practolol. These results further emphasize the difficulties in classifying the lipolytic response of adipose tissue to beta-adrenergic agonists and antagonists within a uniform beta-receptor theory.