IDENTIFICATION OF PROSTANOID RECEPTORS IN RABBIT NONPIGMENTED CILIARYEPITHELIAL-CELLS

Preliminary ligand binding studies demonstrated that the membrane prep arations of the rabbit nonpigmented ciliary epithelial cell line have H-3-prostaglandin E(2) binding sites. The binding sites were specific for H-3-prostaglandin E(2) as demonstrated by competition with unlabel ed prostaglandin E(2). The IC50 of prostaglandin E(2) for the inhibiti on of H-3-prostaglandin E(2) binding was 435 nM. The stimulation of ad enylyl cyclase and phospholipase C by prostanoid receptor agonists, in rabbit non-pigmented ciliary epithelial cells resulted in the formati on of either cyclic AMP or inositol phosphates. Prostaglandin E(2) and 16-16-dimethyl prostaglandin E(2) (both are EP(1), EP(2), EP(3) and E P(4) receptor agonists), 11-deoxy prostaglandin E(1) (EP(2), EP(3) and EP(4) receptor agonist), butaprost (EP(2) receptor agonist), and pros taglandin D-2 (DP receptor agonist) stimulated the formation of cyclic AMP in a dose-dependent manner. Maximal stimulation occurred between 1.25 and 2.5 mu M for prostaglandin E(2) and 16,16-dimethyl prostaglan din E(2) and between 10 and 20 mu M for 11-deoxy prostaglandin E(1) an d prostaglandin D-2. Prostaglandin E(2) and 16,16-dimethyl prostagland in E(2) were more potent (EC(50) of 0.25 mu M and 0.42 mu M respective ly) than 11-deoxy prostaglandin E(1), butaprost or prostaglandin D-2. The formation of cyclic AMP by prostaglandin D-2 was inhibited by BW86 8C, a highly selective DP receptor antagonist. 17-phenyl trinor prosta glandin E(2), prostaglandin F-2 alpha and U46619, the EP(1), FP and TP receptor agonists, respectively stimulated phospholipase C (as measur ed by the formation of total inositol phosphates) in a dose-dependent manner. The agonists 11-deoxy prostaglandin E(1) and butaprost coupled to adenylyl cyclase via guanine nucleotide binding protein, G(s), did not increase the turnover of inositol phosphates. The results of the present study suggest that rabbit non-pigmented ciliary epithelial cel ls express EP(1), EP(2), DP, FP and TP receptors. (C) 1996 Academic Pr ess Limited