The effects of gestational age and intrafetal ACTH administration on the concentration of progesterone in the fetal membranes, endometrium, and myometrium of pregnant sheep.
To examine the hypothesis that progesterone withdrawal from intrauterine tissues is a prerequisite to spontaneous labour or labour induced by administering ACTH to the ovine fetus, we measured the concentration of progesterone in amnion, chorion, endometrium, and myometrium of sheep at different stages of pregnancy and during ACTH-induced labour. There was no significant change in the concentration of progesterone nor in the progesterone:estradiol ratio in amnion or chorion in association with either spontaneous or ACTH-induced labour. The concentration of progesterone in endometrium rose significantly between days 50-60 and days 130-135 of gestation and decreased at term. There was also a fall in the progesterone:estradiol ratio in endometrium between days 130-135 and term. Neither the progesterone concentration not the progesterone:estradiol ratio changed in endometrium during ACTH-induced labour. In the myometrium the concentration of progesterone rose significantly between days 50-60 and day 100 of pregnancy and decreased between day 100 and days 130-135, with a further decline towards term. After intrafetal ACTH there was no change in the concentration of progesterone in the myometrium, although there was a fall in the progesterone:estradiol ratio. We conclude that labour occurring spontaneously at term is associated with a decrease in the progesterone concentration of maternal intrauterine tissues, the myometrium and endometrium. In contrast, there is no decline in the progesterone concentrations of the fetal membranes, the amnion and chorion.(ABSTRACT TRUNCATED AT 250 WORDS)
D000324:Adrenocorticotropic Hormone / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D004717:Endometrium / Q000378:metabolism*; D004967:Estrogens / Q000378:metabolism; D005321:Extraembryonic Membranes / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000378:metabolism*; D005865:Gestational Age; D007751:Labor, Induced; D009215:Myometrium / Q000378:metabolism*; D011247:Pregnancy; D011374:Progesterone / Q000378:metabolism*; D011863:Radioimmunoassay; D012756:Sheep
D004967:Estrogens; D011374:Progesterone; D000324:Adrenocorticotropic Hormone