PROSTAGLANDIN RECEPTORS COUPLED TO ADENYLYL CYCLASE IN THE IRIS CILIARY BODY OF RABBITS, CATS AND COWS

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 PGE2 and PGF2α stimulated adenylyl cyclase but only at high concentrations (> 5 μM). The order of potency of the agonists was dimethyl PGE2 > PGE2 > 11-deoxy PGE1 = PGD2 > iloprost > PGF2α. The DP receptor antagonist BWA868C had no effect on EP agonist responses, indicating that PGE2, dimethyl PGE2 and 11-deoxy PGE1 were not stimulating DP receptors. In the cat, PGE2, dimethyl PGE2 and 11-deoxy PGE1, were all equally potent in stimulating adenylyl cyclase. The order of potency in the cow was PGE2 > dimethyl PGE2 > 11-deoxy PGE1. However, PGD2, iloprost, 17-phenyl trinor PGE2 and PGF2α 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 EP2 receptor subtype appears to predominate; such a predominance of EP2 receptors was not observed in the cat and cow. © 1993 Academic Press. All rights reserved.