title: The distribution of (-)-propranolol in the isolated rabbit iris.
abstract: It has been postulated that propranolol lowers the intraocular pressure by adrenergic neurone block. However, in the isolated iris of albino rabbits, there was only a small degree of cocaine-sensitive (i.e., neuronal) accumulation of 3H-(-)-propranolol, and none at all after pretreatment of the animals with reserpine. Moreover, after preloading of the iris with 3H-(-)-propranolol, veratridine failed to release any labelled material. Hence, any adrenergic neurone blocking action of propranolol is highly unlikely. Albino and pigmented irides were first exposed to 3H-(-)-propranolol and then washed out. The results and their compartmental analysis indicated an extensive binding of 3H-(-)-propranolol in or at pigment cells; the binding is characterized by a low dissociation constant. It is very likely that the initial binding and the subsequent slow dissociation from pigment cells explains the long duration of action of beta-adrenoceptor antagonists in human therapy.
mesh_terms: D000417:Albinism / Q000378:metabolism; D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D066298:In Vitro Techniques; D007498:Iris / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D011433:Propranolol / Q000378:metabolism*; D011817:Rabbits; D012016:Reference Values; D013237:Stereoisomerism; D013997:Time Factors; D014018:Tissue Distribution; D014316:Tritium; D014701:Veratridine / Q000494:pharmacology
chemical_list: D014316:Tritium; D014701:Veratridine; D011433:Propranolol; D003042:Cocaine; D009638:Norepinephrine