Inhibitory prostanoid EP receptors in human non-pregnant myometrium

Abstract

Prostanoid EP receptor agonists relaxed cloprostenol-stimulated contraction of human non-pregnant myometrium in vitro with pEC 50 values of ( n=4): prostaglandin E 2, 7.8±0.2>1-OH prostaglandin E 1, 7.2±0.3>misoprostol, 6.6±0.1>16,16-dimethyl prostaglandin E 2, 6.3±0.7>butaprost, 5.7±0.3>11-deoxy prostaglandin E 1, 5.5±0.2=AH13205 ((±)- trans-2-[4-(1hydroxyhexyl)phenyl]-5-oxocyclopentaneheptanoic acid), 5.5±0.2. The EP 4 receptor antagonist AH23848B ([1α(z), 2β5α]-(±)-7-[5-[[(1,1′-biphenyl)-4-yl]methoxy]-2-(4-morpholinyl)-3-oxo-cyclopentyl]-4-heptenoic acid) (29 μM) had no effect on concentration–effect curves to the EP receptor agonists. The mixed prostanoid receptor antagonist AH6809 (6-isopropoxy-9-oxaxanthene-2-carboxylic acid) competitively antagonised prostaglandin E 2 with a p A 2 of 5.6±0.2. AH6809 (42 μM) antagonised misoprostol, 11-deoxy prostaglandin E 1, and the prostanoid DP receptor agonist BW245C (5-(6-carboxyhexyl)-1-(3-cyclohexyl-3-hydroxypropyl)hydantoin) with apparent p A 2 values of 5.6±0.3, 5.1±0.9 and 5.9±0.4 ( n=4), respectively, but was ineffective against the IP receptor agonist cicaprost ( n=4). The prostanoid DP receptor antagonist BW A868C (3-benzyl-5-(6-carboxyhexyl)-1-(2-cyclohexyl-2-hydroxyethylamino)hydantoin) (50 nM) had no effect on responses to prostaglandin E 2 or misoprostol. The presence of an AH6809-sensitive, AH23848B- and BW A868C-insensitive mechanism is consistent with the hypothesis that inhibitory EP receptor agonists cause relaxation of human non-pregnant myometrium by an EP 2 receptor-mediated process.