[Quantitative autoradiography with (125I)cyanopindolol of ocular tissues]

In the present study beta-adrenergic receptors were identified and localized by autoradiographic methods using [125I]cyanopindolol in human eyes, as well as in the eyes of marmosets and albino rabbits. Quantification revealed that the highest binding-site densities are in the ciliary body and the corneal epithelium and endothelium. Moreover, the iris and conjunctiva showed significant amounts of specific [125I]cyanopindolol binding. In pigmented human and marmoset eyes, binding to the ciliary epithelium and iris was not inhibited by 10 microM propranolol, thus representing nonspecific binding sites. In nonpigmented rabbit eyes, binding to all parts of the eye was reduced to the level of background by 10 microM propranolol and 100 nM ICI 118-551, which is a highly selective beta 2-adrenergic ligand. Being selective for serotonin1B receptors, 100 nM ICI 89-406 which blocks more than 95% of the beta 1-adrenergic receptors, and RU 24,969 have no effect on [125I]cyanopindolol binding, which suggests that there is binding to beta 2-adrenergic receptors. The anatomical location and quantification of beta 2-receptors in the mammalian eye may contribute to better understanding of beta 2-adrenoceptor function and the action of beta-adrenoceptor blocking agents in glaucoma therapy.