Chorion releases a factor that inhibits oxytocin-stimulated myometrial contractility in the pregnant guinea pig

Author： Carvajal Jorge A. Buhimschi Irina A. Thompson Loren P. Aguan Kripamoy Weiner Carl P.

ISSN： 1460-2350

Source： Human Reproduction, Vol.16, Iss.4, 2001-04, pp. : 638-643

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Abstract

It was postulated that chorion releases a substance necessary for the maintenance of uterine quiescence during pregnancy. A decrease in the release of this substance at the end of the pregnancy would be necessary for normal myometrial activation. This hypothesis was tested by demonstrating the ability of chorion to inhibit oxytocin-stimulated myometrial contractility in vitro. Tissues were obtained from timed pregnant Duncan-Hartley guinea pigs either at pre-term or near-term gestation. Myometrial strips were placed in organ baths for isometric tension measurement and contractions stimulated by oxytocin (10^–8 mol/l). Fetal membranes or conditioned medium from chorion were added directly to the organ bath. Near-term chorion and chorion conditioned-medium decreased oxytocin-stimulated contractile activity to 39% and 49% respectively. Neither pre-term nor near-term amnion reduced oxytocin-stimulated myometrial contractile activity. Relaxation induced by pre-term chorion was greater than near-term chorion (23% and 41% of the oxytocin-induced basal level respectively; P < 0.05).="" further,="" chorion-induced="" relaxation="" was="" independent="" of="" the="" gestational="" age="" of="" the="" myometrium.="" human="" chorion="" from="" a="" term,="" not-in-labour="" woman="" also="" inhibited="" oxytocin-stimulated="" guinea="" pig="" myometrial="" contractility.="" it="" was="" concluded="" that="" the="" chorion="" releases="" a="" substance="" or="" substances="" that="" reduce="" oxytocin-stimulated="" myometrial="" contractility="" and="" may="" be="" involved="" in="" the="" maintenance="" of="" uterine="" quiescence="" during="" pregnancy.="">