Khan-Dawood F S
Department of Obstetrics and Gynecology, University of Illinois College of Medicine, Chicago 60612.
Am J Obstet Gynecol. 1987 Dec;157(6):1333-7. doi: 10.1016/s0002-9378(87)80219-3.
To determine the role of placental progesterone in the onset of labor, tissue progesterone concentrations and in vitro conversion of tritiated pregnenolone to progesterone were examined in the placentas, chorion, and amnion of 12 term pregnancies delivered by cesarean section with or without labor and vaginal delivery. In all instances, the placenta had significantly higher progesterone concentrations than the chorion or amnion. Progesterone concentrations in the chorion were significantly lower after the onset of labor than before. The placenta and chorion but not the amnion converted pregnenolone to progesterone; the placenta had a significantly greater conversion rate than the chorion in all instances. Placental conversion of pregnenolone to progesterone increased significantly after labor to reach a maximum with vaginal delivery. Chorionic conversion of pregnenolone to progesterone was significantly increased after vaginal delivery but was similar after cesarean section with or without labor. The reduced tissue progesterone in the chorion, together with enhanced placental and chorionic production of progesterone from its precursor, pregnenolone, suggest that rapid metabolism and increased binding of progesterone locally in the placenta and membranes may lead to the local withdrawal or decline of progesterone and onset of labor.
为确定胎盘孕酮在分娩发动中的作用，我们检测了12例足月妊娠剖宫产分娩（有无临产）及阴道分娩的胎盘、绒毛膜和羊膜组织中的孕酮浓度，以及氚标记孕烯醇酮向孕酮的体外转化情况。在所有情况下，胎盘的孕酮浓度均显著高于绒毛膜或羊膜。临产开始后，绒毛膜中的孕酮浓度显著低于临产之前。胎盘和绒毛膜可将孕烯醇酮转化为孕酮，而羊膜则不能；在所有情况下，胎盘的转化率均显著高于绒毛膜。临产之后，胎盘将孕烯醇酮转化为孕酮的能力显著增强，在阴道分娩时达到最大值。阴道分娩后，绒毛膜将孕烯醇酮转化为孕酮的能力显著增强，但剖宫产分娩（有无临产）后则相似。绒毛膜中组织孕酮的减少，以及胎盘和绒毛膜由其前体孕烯醇酮产生孕酮的能力增强，提示胎盘和胎膜中孕酮的快速代谢及局部结合增加，可能导致孕酮在局部的撤退或减少，从而引发分娩。
