Lens beta-adrenergic receptors. Functional coupling to adenylate cyclase and photoaffinity labeling.

Beta-adrenergic drugs affect lens epithelial and fiber cells. The regulation and cellular integration of lens beta-adrenergic responses are largely unknown. These studies further characterize beta-adrenergic receptors in lens cells with respect to cyclic adenosine monophosphate (cAMP) production and identification of receptor polypeptides. Stimulation of beta-adrenergic receptors in organ-cultured chick lenses resulted in dose-dependent increases in intracellular cAMP levels. Isoproterenol-elicited cAMP accumulation was found in both epithelial/superficial fiber cells and cortical fiber cells. Hormonal stimulation also apparently initiated additional mechanisms involved in the regulation of cAMP levels (ie, phosphodiesterase activation/receptor desensitization). Individual receptor polypeptides were identified in epithelial and fiber membranes with the photoaffinity probe 125I-iodocyanopindolol diazarine. The probe specifically labeled distinct populations of receptor polypeptides in the two cell types. Lens beta-adrenergic receptors were also shown to bind (-) stereoisomers of adrenergic ligands preferentially. These results indicate that differentiating fiber cells are hormonally sensitive to beta-adrenergic stimulation and that epithelial and fiber cells may respond differentially to beta-adrenergic drugs, at least in part, because of their distinct receptor polypeptides.