Prostaglandin Receptors Coupled to Adenylyl Cyclase in the Iris-Ciliary Body of Rabbits, Cats and Cows

Abstract

Stimulation of adenylyl cyclase by prostaglandin (PG) receptor agonists was examined in the iris-ciliary body of rabbits, cats and cows. Iris-ciliary bodies were incubated with or without agonists in Krebs pyruvate buffer containing protease and cyclooxygenase inhibitors. The formation of cAMP in a 15-min period in response to the agonists was measured. In the rabbit iris-ciliary body, all PG receptor agonists at concentrations of 0·062-10·0 μM with the exception of sulprostone stimulated adenylyl cyclase. In this species, 17-phenyl trinor PGE 2 and PGF 2α stimulated adenylyl cyclase but only at high concentrations (> 5 μM). The order of potency of the agonists was dimethyl PGE 2 > PGE 2 > 11-deoxy PGE 1 = PGD 2 > iloprost > PGF 2α. The DP receptor antagonist BWA868C had no effect on EP agonist responses, indicating that PGE 2, dimethyl PGE 2 and 11-deoxy PGE 1 were not stimulating DP receptors. In the cat, PGE 2, dimethyl PGE 2 and 11-deoxy PGE 1, were all equally potent in stimulating adenylyl cyclase. The order of potency in the cow was PGE 2 > dimethyl PGE 2 > 11-deoxy PGE 1. However, PGD 2, iloprost, 17-phenyl trinor PGE 2 and PGF 2α were inactive in this species. The results of this study indicate that EP receptor agonists stimulate adenylyl cyclase in the iris-ciliary body of the three species: stimulation by other agonists depends on the species. In the rabbit, the EP 2 receptor subtype appears to predominate; such a predominance of EP 2 receptors was not observed in the cat and cow.