Induction of parturition by cortisol: effects on negative feedback sensitivity and plasma CRF.

摘要: In fetal sheep, plasma concentrations of both adrenocorticotropic hormone (ACTH) and cortisol increase at the end gestation. The in concentration induces placental 17 alpha-hydroxylase 17, 20 lyase activities therefore stimulates placenta to secrete relatively more estrogen less progesterone. resultant estrogen-to-progesterone ratio is thought uterine contractility initiate labour. We had previously demonstrated that efficacy cortisol-induced suppression ACTH secretion gestation was reduced. hypothesized stimulation steroidogenesis promoted a steroid which reduced negative feedback efficacy, allowed simultaneously. Others proposed corticotrophin releasing factor, might also stimulate secretion. This study designed test hypotheses reduces its own or CRF Five pregnant ewes with twin pregnancies were studied after chronic catheterization. One fetus subjected infusion hydrocortisone sodium succinate (10 micrograms/min, iv) other saline. After 5 53 h infusion, each period hypotension produced by nitroprusside. decreased progesterone circulation into infused, maternal circulation. Fetal increased on third day fetuses went labour.(ABSTRACT TRUNCATED AT 250 WORDS)