Abstract：
For adult anuran amphibians, the kidney and urinary bladder play important osmoregulatory roles through water reabsorption. In the present study, we have examined ontogenetic expression of aquaporins, i.e., AQP2, AQPamU (AQP6ub, AQPa2U), and AQP3, in these organs using the Japanese tree frog, Dryophytes japonicus. Immunohistochemistry using the metamorphosing larvae at stages 40-43 localized AQP2 protein to the collecting ducts in the dorsal zone of the mesonephric kidney. At prometamorphic stages 40 and 41, labelling of AQP2 protein was observed in the apical/ subapical regions of the collecting duct cells. At climax stages 42 and 43, labels for AQP2 and AQP3 became observed in the apical/subapical regions and basolateral membrane of the collecting duct cells, respectively, as seen in the adults. As for the urinary bladder, immuno-positive labels for AQPamU were localized to the apical/subapical regions of granular cells in the mucosal epithelium at stages 40-43. On the other hand, AQP3 immunoreactivity was hardly observed in the urinary bladder at stage 40, and weakly appeared in many granular cells at stage 41. Thereafter, labels for AQP3 became evident along the basolateral membrane of granular cells at stages 42 and 43, together with AQPamU in the apical/subapical regions. These results suggest that the kidney and urinary bladder might be capable of water reabsorption, via AQP2, AQPamU, and AQP3, at stage 42, contributing to the acclimation of the tree frogs to terrestrial environments.
摘要：
对于成年无双两栖动物，肾脏和膀胱通过水分重吸收发挥重要的渗透调节作用。在本研究中,我们已经检查了水通道蛋白的个体发育表达，即，AQP2,AQPamU(AQP6ub,AQPa2U），和AQP3，在这些器官中使用日本树蛙，日本旱生植物。使用40-43阶段变态幼虫的免疫组织化学将AQP2蛋白定位到中肾肾背侧区的收集管中。在前变质阶段40和41，在收集管细胞的顶端/根尖下区域观察到AQP2蛋白的标记。在高潮阶段42和43，在收集管细胞的顶端/根尖下区域和基底外侧膜中观察到AQP2和AQP3的标记，分别,就像在成年人身上看到的。至于膀胱，AQPamU的免疫阳性标记在40-43阶段定位于粘膜上皮中颗粒细胞的顶端/根尖下区域。另一方面,在40期的膀胱中几乎没有观察到AQP3免疫反应性，在41期的许多颗粒细胞中很少出现AQP3免疫反应性。此后,AQP3的标记在42和43阶段沿颗粒细胞的基底外侧膜变得明显，并且在心尖/心尖下区域出现AQPamU。这些结果表明，肾脏和膀胱可能能够重新吸收水，通过AQP2，AQPamU，和AQP3，在42阶段，有助于树蛙适应陆地环境。
