Cheah S H, Sherwood O D
University of Illinois College of Medicine at Urbana-Champaign 61801.
Endocrinology. 1988 May;122(5):1958-63. doi: 10.1210/endo-122-5-1958.
This study examined the requirement for 17 beta-estradiol (E) and relaxin (R) during the preparturient period (approximately the last 30 h of gestation) for normal parturition and pup survival in the rat. On the evening of day 21 of pregnancy, primiparous Sprague-Dawley rats were bilaterally ovariectomized or sham operated and fitted with Silastic capsules containing one of four doses of E (6.0, 11.4, 45.6, or 68.4 micrograms in sesame oil) or sesame oil only. These rats were also injected sc with either 200 micrograms highly purified porcine R dissolved in 200 microliter 5% beeswax in corn oil or R vehicle three times (approximately 8 to 10-h intervals) beginning at ovariectomy. The durations of straining and delivery were increasingly prolonged with increasing doses of E in the ovariectomized groups that received E but no R. In rats that received the two highest doses of E there was a reduction in the percentage of pups born alive and a reduction in pups surviving on day 2 postpartum, and one or two undelivered fetuses were retained in utero in some animals 3 days postpartum. The administration of R with the two highest doses of E restored all parturition parameters to values not different from those of intact controls. In the absence of both E and R, all measured parturition parameters were abnormal, and administration of R in the absence of E only partially restored them to control values. Two major conclusions are drawn. First, E treatment alone to pregnant rats ovariectomized on day 21 fails to elicit normal parturition; indeed, with increasing doses of E, parturition parameters and pup survival become increasingly adversely affected. Second, R treatment of E-treated ovariectomized rats during the immediate preparturient period restores parturition parameters and pup survival to the levels of intact sham-operated controls.
本研究探讨了大鼠分娩前期（约妊娠最后30小时）正常分娩及幼崽存活对17β-雌二醇（E）和松弛素（R）的需求。妊娠第21天晚上，初产的斯普拉格-道利大鼠双侧卵巢切除或假手术，并植入含四种剂量E（6.0、11.4、45.6或68.4微克溶于芝麻油）之一或仅含芝麻油的硅橡胶胶囊。这些大鼠还在卵巢切除后开始，每隔约8至10小时皮下注射200微克溶于200微升5%玉米油蜂蜡中的高纯度猪R或R赋形剂三次。在接受E但未接受R的卵巢切除组中，随着E剂量增加，用力和分娩时间逐渐延长。接受两种最高剂量E的大鼠，出生时存活幼崽百分比降低，产后第2天存活幼崽数量减少，一些动物产后3天子宫内仍保留一两个未分娩胎儿。两种最高剂量E与R联合使用可使所有分娩参数恢复至与完整对照无差异的值。在缺乏E和R时，所有测量的分娩参数均异常，仅在缺乏E时给予R可使它们部分恢复至对照值。得出两个主要结论。第一，对妊娠第21天卵巢切除的大鼠单独给予E不能引发正常分娩；实际上，随着E剂量增加，分娩参数和幼崽存活受到的不利影响越来越大。第二，在分娩前期对接受E治疗的卵巢切除大鼠给予R可使分娩参数和幼崽存活恢复至完整假手术对照水平。
