Studies on prostaglandin antagonists

Abstract

1 Three prostaglandin antagonists have been examined for their ability to block PGE₂ and PGF_2α on human, guinea-pig and isolated rat gastrointestinal muscle. 2 7-oxa-13-Prostynoic acid was either a non-selective antagonist, or was ineffective on the tissues studied; it had marked spasmogenic activity on the rat fundus. 3 1-Acetyl-2-(8-chloro-10,11-dihydrodibenz (b,f)(1,4) oxazepine-10-carbonyl)hydrazine selectively antagonized the excitatory effects of PGE₂ and PGF_2α in guinea-pig and rat tissues, but not in human muscle. 4 Polyphloretin phosphate selectively antagonized the excitatory effects of prostaglandins in both human and guinea-pig muscle preparations, but it caused stimulation of the rat fundus. 5 All the antagonists lowered the tone in many tissues. They also reduced contractions caused by potassium. 6 None of the compounds blocked the inhibitory effect of PGE₂ on intestinal circular muscle. 7 The implication of these results on the nature of prostaglandin receptors, and the value of each compound as a prostaglandin antagonist are discussed.