Endogenous EP4 prostaglandin receptors coupled positively to adenylyl cyclase in Chinese hamster ovary cells:: pharmacological characterization

The purpose of these studies was to investigate the pharmacology of E-series and selected prostaglandins of other classes on adenylyl cyclase activity in Chinese hamster ovary (CHO) cells expressing an endogenous prostanoid receptor and to compare these responses with those from immortalized human nonpigmented ciliary epithelial (NPE) cells containing the EP2 receptor. 11-deoxy-PGE(2) was the most potent of the 16 prostanoid agonists tested for stimulating cAMP formation with a potency (EC50) value of 26 +/- 6 nM in the CHO cells. The endogenous ligand, PGE(2), exhibited potencies of 40 +/- 7 nM (n = 24) in the CHO cells and 67 +/- 9 nM (n = 46) in the NPE cells. The EP2 receptor agonist, butaprost, produced an EC50 value of 212 +/- 58 nM (n = 4) in the NPE cells while being inactive (EC50 > 10 000 nM, n = 6) in the CHO cells. The EP2 receptor selective antagonists, AH22921 and AH23848B, at a concentration of 30 mu M, caused a 2.2 +/- 0.5 (n = 4) and 8.2 +/- 2.7 (n = 4) fold rightward shift in the PGE(2) concentration-response curves in the CHO cells, yielding apparent pK(b) values of 4.6 +/- 0.6 and 5.3 +/- 0.2 (n = 4), respectively. AH22921 and AH23848B were non-competitive antagonists at the CHO cell EP2 receptor, but did not shift the PGE(2) concentration-response curves in the NPE cells containing the EP2 receptor. These studies have characterized the functional prostaglandin receptors in CHO cells pharmacologically and shown them to be consistent with the EP4 subtype. (C) 2000 harcourt Publishers Ltd.