Antolovich G C, McMillen I C, Robinson P M, Silver M, Young I R, Perry R A
Department of Anatomy, University of Melbourne, Parkville, Australia.
Neuroendocrinology. 1991 Sep;54(3):254-61. doi: 10.1159/000125883.
We have investigated the effect of hypothalamo-pituitary disconnection (HPD) on the maturation of basal ir-ACTH and cortisol concentrations in fetal sheep plasma, and on the development of the anterior pituitary corticotroph population in the last third of gestation. After HPD, fetal plasma ir-ACTH concentrations were significantly elevated, and continued to rise with increasing gestational age. However, despite elevated ir-ACTH concentrations, there was no increase in fetal plasma cortisol concentrations, and parturition was delayed for at least 8 days beyond normal term. Furthermore, HPD resulted in a significant disruption of the maturation of the pars distalis corticotrophs. We also examined the change in fetal plasma concentrations of ir-ACTH and cortisol to exogenous CRF after HPD. There was a significant increase in plasma ir-ACTH in response to CRF administration in the HPD fetuses, which was qualitatively similar to that observed in sham-operated fetuses. In contrast, the plasma cortisol response was less in HPD fetuses when compared to that in sham-operated fetuses. The results of this study demonstrate that ir-ACTH secretion is not maintained by the fetal hypothalamus in the last third of gestation, and that ir-ACTH secretion is tonically inhibited by the hypothalamus during this time. The disconnection of the pituitary from the hypothalamus disrupts the maturation of the pituitary-adrenal axis, thus demonstrating the fundamental importance of the hypothalamo-pituitary axis in the normal maturational cascade which culminates in birth in this species.
我们研究了下丘脑 - 垂体分离（HPD）对胎羊血浆中基础免疫反应性促肾上腺皮质激素（ir-ACTH）和皮质醇浓度成熟的影响，以及对妊娠晚期垂体前叶促肾上腺皮质激素细胞群体发育的影响。HPD后，胎羊血浆ir-ACTH浓度显著升高，并随着胎龄增加持续上升。然而，尽管ir-ACTH浓度升高，但胎羊血浆皮质醇浓度并未增加，分娩延迟至少8天超过正常足月时间。此外，HPD导致远侧部促肾上腺皮质激素细胞成熟显著紊乱。我们还研究了HPD后胎羊血浆中ir-ACTH和皮质醇对外源性促肾上腺皮质激素释放因子（CRF）的反应变化。HPD胎羊在给予CRF后血浆ir-ACTH显著增加，这在性质上与假手术胎羊中观察到的相似。相比之下，与假手术胎羊相比，HPD胎羊的血浆皮质醇反应较小。本研究结果表明，在妊娠晚期，胎羊下丘脑不能维持ir-ACTH分泌，且在此期间下丘脑对ir-ACTH分泌有紧张性抑制作用。垂体与下丘脑的分离破坏了垂体 - 肾上腺轴的成熟，从而证明了下丘脑 - 垂体轴在该物种正常成熟级联反应中的根本重要性，该级联反应最终导致分娩。
