Aspects of placental estrogen synthesis in the pig.

J W Knight
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引用次数: 10

Abstract

Conceptus estrogen synthesis in the pig begins with the d 11 blastocyst and continues throughout pregnancy. Estrogens have been implicated as regulators of numerous in utero events related to conceptus survival and development. Studies conducted in our laboratory indicate that progesterone (P4) production by the porcine placenta increases steadily throughout gestation. Estrone (E1) production is triphasic with peaks between d 14-18, around d 30, and a sustained increase from d 70 until parturition. Addition of pregnenolone (P5) augments in vitro P4 and E1 production by both the placenta and the endometrium. Both estrogen concentrations and the ratio between conjugated and free estrogens change drastically during gestation. Evidence from our laboratory suggests that enhanced and prolonged sulfatase activity by d 90 of gestation, coupled with an increase in sulfatase activity-not a change in aromatase activity-contributes to the rise in free estrogens as parturition approaches. We assessed the relative importance of ovarian versus placental production of P4 as a mediator of prenatal survival, conceptus development, and steroidogenesis by the placenta and endometrium. Among other findings, exogenous administration of the non-aromatizable progestagen medroxyprogesterone acetate (MPA) to ovariectomized (OVX) gilts between either d 20-30 or d 60-70 of gestation did not adversely affect concepts survival or development, in vivo estrogen measurements, or in vitro placental steroidogenesis. We also demonstrated that pregnancy may also be maintained during d 20-30 and d 60-70 in OVX gilts administered large quantities of P5 exogenously, presumably due to placental P4 production. Recent studies have examined variables of region of the placenta and intrauterine position on conceptus development, and placental and endometrial steroidogenesis under normal and crowded intrauterine conditions. Results indicated 1) a differential release of P4 and E1 by different regions of the placenta at certain days of gestation, 2) no compensatory increase in steroidogenic activity of the pig placenta when total placental mass was reduced, and 3) a less pronounced effect of intrauterine position on steroidogenic activity in the pig compared with other litter-bearing species.

猪胎盘雌激素合成的几个方面。
母猪妊娠期雌激素合成始于11 d囊胚,并持续整个妊娠期。雌激素被认为是许多与妊娠生存和发育有关的子宫内事件的调节因子。在我们实验室进行的研究表明,在整个妊娠期间,猪胎盘产生的黄体酮(P4)稳步增加。雌酮(E1)的产生是三期的,在第14-18天和第30天左右达到峰值,从第70天开始持续增加,直到分娩。添加孕烯醇酮(P5)可增加胎盘和子宫内膜体外产生P4和E1。在妊娠期间,雌激素浓度和结合雌激素与游离雌激素的比例都发生了巨大的变化。我们实验室的证据表明,在妊娠90 d时,硫酸盐酶活性的增强和延长,加上硫酸盐酶活性的增加——而不是芳香化酶活性的变化——有助于分娩时游离雌激素的增加。我们评估了卵巢与胎盘产生P4的相对重要性,作为产前生存、妊娠发育和胎盘和子宫内膜类固醇生成的中介。在其他研究结果中,在妊娠20-30天或60-70天期间,外源性给予去卵巢(OVX)母猪非芳香化孕激素醋酸羟孕酮(MPA)不会对概念的生存或发育、体内雌激素测量或体外胎盘类固醇生成产生不利影响。我们还证明,外源性给予大量P5的OVX后备母猪,妊娠也可能维持在第20-30天和第60-70天,可能是由于胎盘P4的产生。最近的研究检查了在正常和拥挤的宫内条件下,胎盘区域和宫内位置对妊娠发育以及胎盘和子宫内膜甾体生成的影响。结果表明:1)P4和E1在妊娠特定天数胎盘不同部位的释放存在差异;2)当胎盘总质量减少时,猪胎盘的甾体生成活性没有代偿性增加;3)与其他产仔动物相比,子宫位置对猪的甾体生成活性的影响不明显。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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