Influences on the density of beta-adrenergic receptors in the cornea and iris--ciliary body of the rabbit

Abstract

By measurement of the specific binding of 3H-dihydroalprenolol, the densities of beta-adrenergic receptors on membranes prepared from homogenized corneas and iris--ciliary bodies of rabbits were studied. Sympathetic denervation, as a result of subconjunctival treatment with 6-hydroxydopamine, causes an increase in the density of beta-adrenergic receptors in membranes prepared from the ipsilateral iris--ciliary body but not the cornea. Topical treatment with epinephrine for 5 days causes a decrease in the density of beta-adrenergic receptors in membranes prepared from cornea and iris-ciliary body, whereas similar treatment with timolol causes an increase in the density of beta-adrenergic receptors. In the cornea, the decrease in receptor density that occurs following in vivo treatment with epinephrine is associated with a decreased ability to synthesize cyclic AMP, whereas the increase in receptor density that occurs following in vivo treatment with timolol is not associated with an altered ability to synthesize cyclic AMP. Our results indicate that the density of beta-adrenergic receptors in the anterior segment of the eye is inversely related to the level of adrenergic stimulation to the tissue but that the ability of a tissue to synthesize cyclic AMP does not necessarily parallel the change in receptor density.