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

利用影像分析仪系统，包括定量受体放射自显影、原位杂交和免疫组织化学，研究了内皮素受体的分布及其功能。得到的结果如下：(1)将大鼠脑内ET_A和ET_B配体结合位点（功能受体蛋白）的模式划分为3个场；1)两种受体在脑室周围器官、脑垂体前叶、后叶等共定位；2)脑垂体Rathke袋内仅存在ET_A受体等；3)嗅球外丛状层和浦肯野细胞层仅存在ET_B受体。(2)大鼠脑干迷走神经后区、尾侧孤立束核和背侧核均可见ET_A受体蛋白，而ET_A mRNA仅局限于后区。因此，可以考虑在大鼠脑干中存在ET_A神经元从后侧区域投射到迷走神经尾侧孤立束核和背侧核。另一方面，ET_B受体蛋白的分布与ET_B mRNA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受体能够与ET-1结合。因此，ET_A和ET_B受体之间的协同机制可能在识别ET-1这一典型的“二价”配体中起作用。(4) ET_B受体在星形胶质细胞中表达，需要考虑ET_B受体激活星形胶质细胞响应神经元死亡后神经组织修复的可能性。(5)大鼠腹腔巨噬细胞明显表达ET_B受体，而不表达ET_A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.