Role of vascular endothelial growth factor (VEGF) in the formation of vascular system for regulating the adenohyphysial function

垂体前叶激素受下丘脑神经激素调控，下丘脑神经激素产生于下丘脑区，经门静脉输送至远部。垂体门静脉系统是中枢神经系统向垂体传递激素信息的重要通道。已知血管内皮生长因子（VEGF）对内皮细胞有丝分裂作用，并使内皮细胞更具渗透性。本研究采用免疫组织化学和fitc -明胶偶联注射方法，发现激素产生细胞与下丘脑-垂体轴微血管之间存在密切关系。Northern blot检测VEGF mRNA在远端部、脑、肺和肾中表达，远端部最低。原位RT-PCR方法清楚地显示，在胎儿15.5天时，远侧部的吻侧和腹侧区域存在VEGF mrna表达细胞。胎儿18.5天时表达水平下降，但整个腹侧区域均可见阳性细胞。另一方面，微血管在胎儿15.5天时渗透到远部，随后扩张到整个肺叶，形成第二神经丛。这些结果表明，VEGF参与远端部血管的形成，但不参与门静脉的形成，因为门静脉的形成始于胎儿13.5天，在远端部吻侧区域出现VEGF之前。原位RT-PCR和免疫组化双重染色提示部分ACTH细胞具有产生VEGF的潜能。在牛蛙的垂体变态过程中也有类似的发现。我还克隆了虹鳟鱼和牛蛙的VEGF编码cDNA片段。因此，这些数据为下丘脑-垂体轴血管化形成的进化提供了基本线索。

Anterior pituitary hormones are regulated by hypothalamic neurohormones, which are produced in the hypothalamic area and transported to the pars distalis via portal vessels. The hypophyseal portal system provides an important line for carrying hormonal information from the central nervous system to the pituitary. Vascular endothelial growth factor (VEGF) is known to have a mitogenic effect on endothelial cells and renders the endothelium more permeable.The present study using immunohistochemistry and FITC-conjugated to gelatin injection method showed a close relationship between hormone-producing cells and microvessels in hypothalamic-pituitary axis. The Northern blot analysis detected VEGF mRNA in the pars distalis, brain, lung and kidney with the lowest levels in the pars distalis. The in situ RT-PCR method clearly demonstrated the presence of VEGF mRNA-expressing cells in the rostral and ventral regions of the pars distalis at fetal 15.5 day. Expression levels decreased at fetal 18.5 day, but the positive cells were observed throughout the entire ventral region. On the other hand, the microvessels penetrated into the pars distalis at fetal 15.5 day and subsequently expanded into the entire lobe to form the secondary plexus. These results suggest that VEGF is involved in the vascularization of the pars distalis, but not in the formation of portal vessels, because the formation of portal vessels begins at fetal 13.5 day, before the appearance of VEGF in the rostral region of the pars distalis. The dual staining of in situ RT-PCR and immunohistochemistry indicates that some ACTH cells have the potential to produce VEGF. Similar finding was obtained in the bullfrog pituitary glands during metamorphosis. I also cloned cDNA fragments encoding VEGF of rainbow trout and bullfrog. Thus, these data provide fundamental clues in evolutionary aspect of the formation of the vasculalization of hypothalamic-pituitary axis.