Endogenous EP4prostaglandin receptors coupled positively to adenylyl cyclase in Chinese hamster ovary cells: pharmacological characterization

Abstract

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 non-pigmented ciliary epithelial (NPE) cells containing the EP2receptor. 11-deoxy-PGE2was 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, PGE2, exhibited potencies of 40 ± 7 nM (n= 24) in the CHO cells and 67 ± 9 nM (n= 46) in the NPE cells. The EP2receptor agonist, butaprost, produced an EC50value of 212 ± 58 nM (n= 4) in the NPE cells while being inactive (EC50⪢ 10 000 nM, n= 6) in the CHO cells. The EP4receptor selective antagonists, AH22921 and AH23848B, at a concentration of 30 μM, caused a 2.2 ± 0.5 (n= 4) and 8.2 ± 2.7 (n= 4) fold rightward shift in the PGE2concentration-response curves in the CHO cells, yielding apparent pKbvalues of 4.6 ± 0.6 and 5.3 ± 0.2 (n= 4), respectively. AH22921 and AH23848B were non-competitive antagonists at the CHO cell EP4receptor, but did not shift the PGE2concentration-response curves in the NPE cells containing the EP2receptor. These studies have characterized the functional prostaglandin receptors in CHO cells pharmacologically and shown them to be consistent with the EP4subtype.