Characterization of β adrenergic receptors in bovine pigmented ciliary processes

Abstract

To analyse the molecular mechanism of action of β-adrenergic compounds in reducing the intraocular pressure, the binding of ¹²⁵I-iodohydroxybenzylpin-dolol to bovine pigmented ciliary processes was studied. The binding was found to be highly specific, saturable, reversible and displayed stereospe-cificity. Only one class of binding sites was detected. Values for K_D of 0.18 nM and 0.32 nM were derived from kinetic and equilibrium experiments, respectively. The total number of β receptors was large: 1.28 pmoles/mg protein. Competitive inhibition of 125_I-iodohydroxybenzylpindolol binding by agonists and antagonists revealed that the majority of β receptors in bovine pigmented ciliary processes were of the β₂ type. The pharmacological and biochemical characteristics of the binding of adrenergic drugs found in these membranes are consistent with a regulation of aqueous humor production by the β adrenergic system.