Comparison of Cells Expressed Between Functional Endothelin Receptor Proteins and Their mRNAs by Quantitative Imazing Analyzer System

应用免疫组织化学、原位杂交和放射自显影等方法，对内皮素（ET）受体的分布及其功能进行了研究。所得结果如下。(1)大鼠脑内ET_A和ET_B配体结合位点（功能性受体蛋白）的分布可分为3个方面：1）两种受体在脑室周围器官、垂体前叶和后叶等部位共定位; 2)只有垂体Rathke囊等部位有ET_A受体，3)嗅球外丛状层和浦肯野细胞层仅有ET_B受体。(2)ET_A受体蛋白分布于脑干后区、孤束核尾侧和迷走神经背核，而ET_AmRNA仅分布于脑干后区。因此，在大鼠脑干中可能存在从后区投射到孤束核尾侧和迷走神经背核的ET_A神经元。ET_B受体蛋白的分布与ET_B mRNA的分布相似，ET_B受体在胶质细胞中表达。(3)当ET_A受体被ET_A拮抗剂BQ-123占据时，ET_B受体可与ET-1结合。因此，ET_A和ET_B受体之间可能存在一种协同作用机制，参与了对ET-1这种典型的“二价”配体的识别。(4)ET_B受体在星形胶质细胞中有表达，ET_B受体是否能激活星形胶质细胞参与神经元死亡后的修复反应，有待进一步研究。(5)大鼠腹腔巨噬细胞明显表达ET_A受体而不表达ET_B受体。

We investigated the distribution of endothelin (ET) receptors and their functions by using our imazing Analyzer system, including quantitative receptor autoradiography, in situ hybridization and Immunohistochemistry. The obtained results were following.(1) The pattern of ET_A and ET_B ligand binding sites (ftinctional receptor proteins) in the rat brain was classified to 3 fields ; 1) co-localization of both receptors in the circumventricular organs, and anterior and posterior lobes of the pituitary gland, etc., 2) only ET_A receptor in the Rathke pouch of pituitary gland, etc., 3) only ET_B receptor in the external plexiform layer of olfactory bulb and the Purkinje cell layer.(2) ET_A receptor proteins were observed in the area posterior, the caudal solitary tract nucleus and dorsal nucleus of the vagus in rat brainstem, whereas ET_A mRNA was localized to only area posterior. Therefore, the presence of ET_A neurons projected to the caudal solitary tract nucleus and dorsal nucleus of the vagus from the area posterior may be considered in rat brainstem. On the other hand, the distribution of ET_B receptor proteins was similar to that of ET_B mRNA, and the ET_B receptors were expressed in the glia cells.(3) The ET_B receptor was capable of binding ET-1 when ET_A receptor was being occupied by BQ-123, ET_A antagonist. Therefore, A collaboration mechanism between the ET_A and the ET_B receptorS may function in the recognition of ET-1, a typical "bivalent" ligand.(4) The ET_B receptor was expressed in astrocytes, and the possibility the astrocytes can be activated by ET_B receptor in response to neural tissue repair after neuronal death would have to be considered.(5) The rat peritoneal macrophages apparently express the ET_B receptor but not the ET_A receptor.