RESUMO
The effects of infusions of fresh sheep placenta in normal saline and the filtrate obtained therefrom after boiling for 15 min were investigated on guinea-pig and rat uteri, other mammalian non-vascular smooth muscles and the cardiovascular system, noting their responses to the infusion/filtrate in the presence or absence of various inhibitors or agonists. Solvent partition, acute toxicity and thin layer chromatography (TLC) studies were also performed. It was found that the infusion/filtrate had oxytocic activity independent of histamine and muscarinic receptors. It had H(1) receptor activity agonist action on the guinea-pig ileum, antagonized adrenaline-induced contractions in the vas but unlike bradykinin did not relax rat duodenum. It induced vasoconstriction in the rat hindquarters, depressed cat blood pressure but had positive inotropic effect on the guinea-pig Langendorff heart. Only the eluent from the least mobile of the five TLC bands on silica gel had oxytocic activity. It was concluded that the sheep chorionic oxytocic substance is not acetylcholine, histamine, 5-hydroxytryptamine, noradrenaline, adrenaline, prostaglandins F or E but is a peptide, which is not bradykinin, vasopressin or oxytocin.