Effects of Salbutamol and Butoxamine on the Human Fat Cell Adenylate Cyclase

Abstract

In order to characterize the β-adrenoceptors coupled to the human fat cell adenylate cyclase more extensively the effects of the β₂-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 β-adrenoceptors linked to the human fat cell adenylate cyclase than isoproterenol. In addition, the β₂-selective antagonist butoxamine was slightly more potent in inhibiting the isoproterenol-stimulated fat cell enzyme than the cardio-selective β-blocking agent practolol. These results further emphasize the difficulties in classifying the lipolytic response of adipose tissue to β-adrenergic agonists and antagonists within a uniform β-receptor theory.