INVITRO DETERMINATION OF ABILITY OF DRUGS TO BIND TO ADRENERGIC-RECEPTORS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 16  (12) , 1118-1124
Abstract
.alpha.- and .beta.-adrenergic receptors were studied by measuring the binding of 3H-dihydroergocryptine and 3H-dihydroalprenolol, respectively, to membranes prepared from homogenized rabbit iris-ciliary bodies. The binding of 3H-dihydroergocryptine appears to be specific for .alpha.-adrenergic receptors, since adrenergic agents displace this radioligand with the following order of potency: phentolamine > epinephrine .gtoreq. norepinephrine > > isoproterenol = propranolol. The binding of 3H-dihydroalprenolol appears to be specific for .beta.-adrenergic receptors, since adrenergic agents displace this radioligand with the following order of potency: propranolol > > isoproterenol .gtoreq. epinephrine > norepinephrine > > phentolamine. Clonidine and dopamine bind to the .alpha.-adrenergic receptor but have little activity at the .beta.-adrenergic receptor. Timolol, d-isoproterenol and dipivalyl epinephrine bind to the .beta.-adrenergic receptor but have little activity at the .alpha.-adrenergic receptor. In vitro binding assays for .alpha.- and .beta.-adrenergic receptors are useful for studying the mechanism of drug action.