Deauseault D, Giroux D, Wood C E
Department of Physiology, University of Florida College of Medicine, Gainesville 32610-0274, USA.
Neuroendocrinology. 2000 May;71(5):287-91. doi: 10.1159/000054548.
Parturition is initiated in sheep by an increase in the activity of the fetal hypothalamus-pituitary-adrenal (HPA) axis. Prostaglandins, known to augment the activity of this endocrine axis, have long been proposed as involved in the initiation of paturition. We have previously demonstrated that endogenously produced prostanoids augment the activity of the HPA axis, and we have proposed that the increased production of prostanoids within the fetal brain or pituitary at the end of gestation might be involved in the initiation of parturition. An important regulatory step in the biosynthesis of prostanoids is the activity of prostaglandin endoperoxide synthase (PGHS). The present study was designed to test the hypothesis that the abundance of one or both isoforms of PGHS (PGHS-1 and PGHS-2) increase in brain and/or pituitary at the end of gestation. We used immunoblot analysis to measure the abundance of immunoreactive PGHS-1 and PGHS-2 in pituitary, hypothalamus and brainstem collected from fetuses of known gestational ages. We found that the abundance of PGHS-1 was weakly but significantly increased at the end of gestation in the pituitary and brainstem. The abundance of PGHS-2, on the other hand, increased exponentially in the pituitary and hypothalamus with highest concentrations found in term fetuses. We conclude that these enzymes are developmentally regulated in pituitary and in brain regions important for HPA axis control. We speculate that the increased enzyme's abundance results in increased prostanoid biosynthesis near term, and is a link in the chain of events which initiates parturition.
绵羊分娩是由胎儿下丘脑 - 垂体 - 肾上腺（HPA）轴活动增加引发的。前列腺素已知可增强该内分泌轴的活性，长期以来一直被认为与分娩启动有关。我们之前已经证明内源性产生的前列腺素可增强HPA轴的活性，并且我们提出妊娠末期胎儿脑内或垂体中前列腺素产生的增加可能与分娩启动有关。前列腺素生物合成中的一个重要调节步骤是前列腺素内过氧化物合酶（PGHS）的活性。本研究旨在检验以下假设：妊娠末期PGHS（PGHS - 1和PGHS - 2）的一种或两种同工型在脑和/或垂体中的丰度会增加。我们使用免疫印迹分析来测量从已知胎龄胎儿收集的垂体、下丘脑和脑干中免疫反应性PGHS - 1和PGHS - 2的丰度。我们发现，妊娠末期垂体和脑干中PGHS - 1的丰度虽微弱但显著增加。另一方面，PGHS - 2的丰度在垂体和下丘脑呈指数增加，足月胎儿中浓度最高。我们得出结论，这些酶在垂体和对HPA轴控制重要的脑区中受到发育调节。我们推测，酶丰度的增加导致足月时前列腺素生物合成增加，并且是启动分娩的一系列事件中的一个环节。
