Identification of Prostanoid Receptors in Rabbit Non-pigmented Ciliary Epithelial Cells

Abstract

Preliminary ligand binding studies demonstrated that the membrane preparations of the rabbit non-pigmented ciliary epithelial cell line have 3H-prostaglandin E 2binding sites. The binding sites were specific for 3H-prostaglandin E 2as demonstrated by competition with unlabeled prostaglandin E 2. The IC 50of prostaglandin E 2for the inhibition of 3H-prostaglandin E 2binding was 435n m. The stimulation of adenylyl cyclase and phospholipase C by prostanoid receptor agonists, in rabbit non-pigmented ciliary epithelial cells resulted in the formation of either cyclic AMP or inositol phosphates. Prostaglandin E 2and 16-16-dimethyl prostaglandin E 2(both are EP 1, EP 2, EP 3and EP 4receptor agonists), 11-deoxy prostaglandin E 1(EP 2, EP 3and EP 4receptor agonist), butaprost (EP 2receptor agonist), and prostaglandin D 2(DP receptor agonist) stimulated the formation of cyclic AMP in a dose-dependent manner. Maximal stimulation occurred between 1.25 and 2.5μ mfor prostaglandin E 2and 16,16-dimethyl prostaglandin E 2and between 10 and 20μ mfor 11-deoxy prostaglandin E 1and prostaglandin D 2. Prostaglandin E 2and 16,16-dimethyl prostaglandin E 2were more potent (EC 50of 0.25μ mand 0.42μ mrespectively) than 11-deoxy prostaglandin E 1, butaprost or prostaglandin D 2. The formation of cyclic AMP by prostaglandin D 2was inhibited by BW868C, a highly selective DP receptor antagonist. 17-phenyl trinor prostaglandin E 2, prostaglandin F 2αand U46619, the EP 1, FP and TP receptor agonists, respectively stimulated phospholipase C (as measured by the formation of total inositol phosphates) in a dose-dependent manner. The agonists 11-deoxy prostaglandin E 1and 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 cells express EP 1, EP 2, DP, FP and TP receptors.