Characterization of beta adrenergic receptors in bovine pigmented ciliary processes

To analyse the molecular mechanism of action of beta-adrenergic compounds in reducing the intraocular pressure, the binding of 125I-iodohydroxybenzylpindolol to bovine pigmented ciliary processes was studied. The binding was found to be highly specific, saturable, reversible and displayed stereospecificity. Only one class of binding sites was detected. Values for KD of 0.18 nM and 0.32 nM were derived from kinetic and equilibrium experiments, respectively. The total number of beta receptors was large : 1.28 pmoles/mg protein. Competitive inhibition of 125I-iodohydroxybenzylpindolol binding by agonists and antagonists revealed that the majority of beta receptors in bovine pigmented ciliary processes were of the beta 2 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 beta adrenergic system.