Identification of beta-adrenergic sensitive adenylate cyclase in rat thoracic duct

The effect of L-isoproterenol on the 3',5'-cyclic adenosine monophosphate (cAMP) generating system in rat thoracic duct membranes was investigated in order to identify beta-adrenergic receptors. L-Isoproterenol elicited a dose-dependent stimulation of cAMP formation; L-noradrenaline was less effective than L-isoproterenol in stimulating cAMP increase, whereas L-phenylephrine was without important effects on cAMP levels. L-Propranolol, a selective antagonist of beta-adrenergic receptors, caused a dose-dependent decrease of the effects of L-isoproterenol. In contrast, the L-isoproterenol-elicited increase of cAMP was unaffected by the alpha-adrenergic and dopamine receptor-blocking agents phentolamine and haloperidol. These data indicate that L-isoproterenol stimulates cAMP formation in the rat thoracic duct by a specific interaction with beta-adrenergic receptors positively coupled to adenylate cyclase.