Osmotic threshold and sensitivity for vasopressin release and fos expression by hypertonic NaCl in ovine fetus.
Osmotic threshold and sensitivity for vasopressin release and fos expression by hypertonic NaCl in ovine fetus.
复制标题
DOI：
10.1152/ajpendo.2000.279.6.e1207
复制
发表时间：
2000-12
期刊：
影响因子：
--
通讯作者：
Zhice Xu;Calvario Glenda;L. Day;Jiaming Yao;M. Ross
中科院分区：
文献类型：
--
作者：
Zhice Xu;Calvario Glenda;L. Day;Jiaming Yao;M. Ross
在成年人中，高渗刺激中枢血管紧张素受体，导致精氨酸加压素（AVP）分泌。近期胎羊也发展了机制，以响应血管内高渗刺激在子宫内AVP释放。然而，先前证明胎儿AVP分泌的研究利用了比成人垂体诱导的AVP刺激所需的更大的血浆张力变化。我们试图检查近期胎儿血浆渗透压阈值和刺激AVP分泌的敏感性，并将血浆激素水平与中枢神经元反应性相关联。长期仪器绵羊胎仔（130 +/- 2天）和母绵羊同时接受等渗或高渗血管内NaCl输注。母体和胎儿血浆AVP和血管紧张素II（ANG II）水平进行了检查，在逐步增加的血浆高渗水平。静脉注射高渗氯化钠逐渐升高血浆渗透压和钠水平。高渗时母体和胎儿血浆AVP均升高，而ANG II水平无变化。母体血浆AVP水平随血浆渗透压增加3%而显著增加，而胎儿血浆AVP仅在较高的血浆渗透压水平（超过6%）时显著增加。因此，尽管母体和胎儿血浆渗透压阈值相似（302 mosmol/kg vs. 304 mosmol/kg），但母羊AVP与渗透压的回归斜率大于胎儿（0.232 vs. 0.064）。高渗诱导Fos免疫反应（FOS-ir）在胎脑的脑室周围器官。Fos免疫反应也在胎儿视上核和室旁核（SON和PVN）中表达，双标记显示SON和PVN中含AVP的神经元对静脉注射NaCl反应表达Fos。这些结果表明，在绵羊胎儿在妊娠130天，神经内分泌细胞脱水的反应是功能性的，虽然他们的证据与成人相比，AVP分泌的敏感性相对降低。
In adults, hyperosmolality stimulates central osmoreceptors, resulting in arginine vasopressin (AVP) secretion. Near-term fetal sheep have also developed mechanisms to respond to intravascular hypertonicity with stimulation of in utero AVP release. However, prior studies demonstrating fetal AVP secretion have utilized plasma tonicity changes greater than those required for adult osmotically induced AVP stimulation. We sought to examine near-term fetal plasma osmolality threshold and sensitivity for stimulation of AVP secretion and to correlate plasma hormone levels with central neuronal responsiveness. Chronically instrumented ovine fetuses (130 +/- 2 days) and maternal ewes simultaneously received either isotonic or hypertonic intravascular NaCl infusions. Maternal and fetal plasma AVP and angiotensin II (ANG II) levels were examined at progressively increasing levels of plasma hypertonicity. Intravenous hypertonic NaCl gradually elevated plasma osmolality and sodium levels. Both maternal and fetal plasma AVP increased during hypertonicity, whereas ANG II levels were not changed. Maternal AVP levels significantly increased with a 3% increase in plasma osmolality, whereas fetal plasma AVP significantly increased only at higher plasma osmolality levels (over 6%). Thus the slope of the regression of AVP vs. osmolality was greater for ewes than for fetuses (0.232 vs. 0.064), despite similar maternal and fetal plasma osmolality thresholds for AVP secretion (302 vs. 304 mosmol/kg). Hyperosmolality induced Fos immunoreactivity (FOS-ir) in the circumventricular organs of the fetal brain. FOS-ir was also demonstrated in the fetal supraoptic and paraventricular nuclei (SON and PVN), and double labeling demonstrated that AVP-containing neurons in the SON and PVN expressed Fos in response to intravenous NaCl. These results demonstrate that, in the ovine fetus at 130 days of gestation, neuroendocrine responses to cellular dehydration are functional, although they evidence a relatively reduced sensitivity for AVP secretion compared with the adult.