Myers D A, Bell M E, McDonald T J, Myers T R
Department of Physiology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
Endocrinology. 1999 Sep;140(9):4292-9. doi: 10.1210/endo.140.9.6949.
Both the capacity of CRF to release ACTH and the number of binding sites for CRF in the anterior pituitary decline during the final weeks of gestation in fetal sheep. The present study examined regulation of pituitary CRF receptor expression by the hypothalamic paraventricular nucleus (PVN) during late gestation in fetal sheep. Bilateral radiofrequency lesions of the PVN (PVN-Lx; n = 4) or sham lesions (SHAM; n = 5) were performed in fetal sheep at 118-122 days of gestational age (dGA). Pituitary glands from PVN-Lx and SHAM fetuses were collected at 139-142 dGA (term, approximately 148 dGA). Dual-label in situ hybridization was performed using a digoxigenin-labeled ovine POMC complementary RNA, together with a 35S-labeled ovine CRF type I (CRF1) receptor complementary RNA, to localize and quantify CRF1 receptor mRNA in POMC-hybridizing cells. Binding of [125I]-ovine CRF was also examined in the fetal pituitary of both PVN-Lx and SHAM fetuses using in situ autoradiography. The hybridization signal for the CRF1 receptor mRNA was primarily restricted to POMC-expressing cells in the anterior pituitary of both PVN-Lx and SHAM fetuses; no hybridization signal for the CRF1 receptor was observed in the neurointermediate lobe (NIL) in either group. The hybridization signal for CRF1 receptor mRNA in anterior pituitary corticotropes of PVN-Lx fetuses was significantly lower in both the inferior and superior regions of the anterior pituitary, compared with SHAM fetuses (P < 0.05). In the inferior region of the anterior pituitary, the percentage of POMC-hybridizing cells containing CRF1 receptor hybridization signal was significantly greater in PVN-Lx (90+/-7%; mean +/- SEM), compared with SHAM (67+/-6%; P < 0.05) fetuses. No differences in the percentage of POMC cells containing CRF1 receptor hybridization signal were observed in the superior region of the anterior pituitary between PVN-Lx (89+/-8%) and SHAM (87+/-9%). Binding of [125I]-ovine CRF (oCRF) was significantly greater in anterior pituitaries of PVN-Lx (140+/-19 mean arbitrary densitometry U +/- SEM), compared with SHAM (73+/-23; P < 0.05) fetuses. For both PVN-Lx and SHAM fetuses, there were no differences within group in [125I]-oCRF binding between the inferior and superior regions of the anterior pituitary. A weak, but significant (P < 0.05), autoradiographic signal for [125I]-oCRF binding was observed in the NIL of both SHAM and PVN-Lx fetal sheep. The level of [125I]-oCRF binding was significantly lower in the NIL, compared with anterior pituitary, for both SHAM (P < 0.01) and PVN-Lx fetuses. There were no differences in [125I]-oCRF binding in the NIL between SHAM and PVN-Lx fetal sheep. Our findings support a role for the PVN in regulating anterior pituitary CRF1 receptor expression in the late-gestation sheep fetus.
在妊娠后期，胎羊垂体促肾上腺皮质激素释放激素（CRF）释放促肾上腺皮质激素（ACTH）的能力以及垂体前叶CRF结合位点的数量均下降。本研究检测了妊娠后期胎羊下丘脑室旁核（PVN）对垂体CRF受体表达的调节作用。在妊娠118 - 122天（dGA）对胎羊进行PVN双侧射频损毁（PVN-Lx；n = 4）或假损毁（SHAM；n = 5）。在139 - 142 dGA（足月约148 dGA）采集PVN-Lx和SHAM胎羊的垂体。采用地高辛标记的绵羊阿黑皮素原（POMC）互补RNA与35S标记的绵羊CRF I型（CRF1）受体互补RNA进行双重标记原位杂交，以定位并定量POMC杂交细胞中的CRF1受体mRNA。同时，利用原位放射自显影技术检测PVN-Lx和SHAM胎羊垂体中[125I] - 绵羊CRF的结合情况。PVN-Lx和SHAM胎羊垂体前叶中，CRF1受体mRNA的杂交信号主要局限于表达POMC的细胞；两组神经中间叶（NIL）均未观察到CRF1受体的杂交信号。与SHAM胎羊相比，PVN-Lx胎羊垂体前叶促肾上腺皮质激素细胞中，垂体前叶上下区域CRF1受体mRNA的杂交信号均显著降低（P < 0.05）。在垂体前叶下部区域，PVN-Lx胎羊中含有CRF1受体杂交信号的POMC杂交细胞百分比（90±7%；均值±标准误）显著高于SHAM胎羊（67±6%；P < 0.05）。在垂体前叶上部区域，PVN-Lx胎羊（89±8%）和SHAM胎羊（87±9%）之间，含有CRF1受体杂交信号的POMC细胞百分比无差异。与SHAM胎羊（73±23；P < 0.05）相比，PVN-Lx胎羊垂体前叶中[125I] - 绵羊CRF（oCRF）的结合显著增加（140±19平均任意光密度单位±标准误）。对于PVN-Lx和SHAM胎羊，垂体前叶上下区域之间[125I] - oCRF结合在组内均无差异。在SHAM和PVN-Lx胎羊的NIL中均观察到较弱但显著的（P < 0.05）[125I] - oCRF结合放射自显影信号。与垂体前叶相比，SHAM和PVN-Lx胎羊NIL中[125I] - oCRF结合水平均显著降低（P < 0.01）。SHAM和PVN-Lx胎羊NIL中[125I] - oCRF结合无差异。我们的研究结果支持PVN在调节妊娠后期绵羊胎儿垂体前叶CRF1受体表达中发挥作用。
