HUMAN CILIARY PROCESS ADRENERGIC-RECEPTOR - PHARMACOLOGICAL CHARACTERIZATION

  • 1 January 1981
    • journal article
    • research article
    • Vol. 21  (6) , 798-804
Abstract
To better understand the nature of interaction of various amines with adrenergic receptors in the human ciliary process, .beta.-adrenergic-stimulated adenylate cyclase activity was characterized in broken cell preparations of this tissue from donor eyes. Among various agonists, isoproterenol was the most potent activator of enzyme activity (Ka [activation concentration] = 3.4 .times. 10-7 M), followed in order by epinephrine (Ka = 2.7 .times. 10-6 M), norepinephrine (Ka = 2.1 .times. 10-5 M) and phenylephrine (Ka > 10-4 M). Isoproterenol-stimulated enzyme activity was blocked by timolol (Ki [inhibition constant] = 3.4 .times. 10-9 M), IPS 339 (tert-butylamino-3-ol-2-propyl)oximino-9-fluorine] (Ki = 4.4 .times. 10-9 M), H35/25 [4-dimethyl-N-isopropyl phenylethanolamine] (Ki = 6.9 .times. 10-7 M) and atenolol (Ki = 1.4 .times. 10-5 M). The human ciliary processes contain a predominance of .beta.2-adrenergic receptors. The findings are relevant to physiological studies of aqueous humor secretion and to the potential development of adrenergic agents with greater specificity for the .beta.-adrenergic receptor.