Regulation of Lens β-Adrenergic Receptors by Receptor Occupancy and Dexamethasone

Abstract

ABSTRACT

ß-adrenergic binding sites in primary cultures of chick lens annular pad (CLAP) cells were characterized with dihydroalprenolol (DHAP). Binding site affinities and densities were similar to ß-adrenergic receptors (ßARs) previously characterized on crude membranes from freshly isolated cells. In competitive displacement studies, the ß-blocker propranolol was shown to increase the number of available binding sites in a concentration dependent manner. Acute exposure of CLAP cells to propranolol prior to DHAP binding also resulted in an increase in the number of available binding sites. Finally, lens ß-adrenergic binding site levels could be modulated by dexamethasone treatment. These results indicate that lens ßARs are subject to common regulatory mechanisms and further implicate ophthalmic pharmaceuticals as possible cataractogenic agents.