中文摘要：

内分泌激素是维持妊娠和启动分娩的重要因素。孕激素是静息子宫、维持妊娠的主要激素,而糖皮质激素、前列腺素和雌激素等激素则与分娩启动密切相关。孕激素水平的下降是很多哺乳类动物分娩启动的前提条件,然而有些哺乳类动物包括灵长类在整个妊娠过程包括分娩中均维持着高水平的孕激素,此现象令人费解。越来越多的证据表明,人类分娩启动时孕激素同样出现了撤退,但是发生在孕激素的受体水平,主要表现为孕激素受体亚型表达比值和孕激素受体转录辅助因子表达的改变。本文比较了人类和其它哺乳类动物分娩启动时孕激素撤退的三种模式,即黄体溶解、胎盘P450c17羟化酶上调和孕激素受体功能改变,旨在进一步阐明人类分娩启动机制,从而为防治早产提供新的思路。

英文摘要：

Endocrine hormones are important factors in maintaining pregnancy as well as initiation of parturition.Progesterone is the major hormone maintaining myometrium quiescence,while glucocorticoids,prostaglandins and estrogen are among the major hormones involved in the initiation of parturition.Therefore progesterone withdrawal at the end of pregnancy is the prerequisite for the initiation of parturition.However,unlike most of the other species of mammals that the withdrawal of progesterone is achieved via reduction of progesterone synthesis or increased conversion of progesterone to estrogen,some mammals including the primates maintain high progesterone level throughout gestation and even during parturition.Accumulating lines of evidence indicate that the withdrawal of progesterone in human being is attained via the changes of the expression ratio of progesterone receptor subtypes and the changes of co-activators required for the activation of transcriptional activity of progesterone receptor.Here we reviewed the three major mechanisms,namely luteolysis,upregulation of placental P450c17 hydroxylase and changes of progesterone receptor functions,underlying progesterone withdrawal in late pregnancy in mammals.