Department of Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
Horm Behav. 2010 Aug;58(3):457-64. doi: 10.1016/j.yhbeh.2010.05.007. Epub 2010 May 17.
Angiotensin II (Ang II) stimulates oral water intake by causing thirst in all terrestrial vertebrates except anurans. Anuran amphibians do not drink orally but absorb water osmotically through ventral skin. In this study, we examined the role of Ang II on the regulation of water-absorption behavior in the Japanese tree frog (Hyla japonica). In fully hydrated frogs, intracerebroventricular (ICV) and intralymphatic sac (ILS) injection of Ang II significantly extended the residence time of water in a dose-dependent manner. Ang II-dependent water uptake was inhibited by ICV pretreatment with an angiotensin II type-1 (AT(1)) receptor antagonist but not a type-2 (AT(2)) receptor antagonist. These results suggest that Ang II stimulates water-absorption behavior in the tree frog via an AT(1)-like but not AT(2)-like receptor. We then cloned and characterized cDNA of the tree frog AT(1) receptor from the brain. The tree frog AT(1) receptor cDNA encodes a 361 amino acid residue protein, which is 87% identical to the toad (Bufo marinus) AT(1) receptor and exhibits the functional characteristics of an Ang II receptor. AT(1) receptor mRNAs were found to be present in a number of tissues including brain (especially in the diencephalon), lung, large intestine, kidney and ventral pelvic skin. When tree frogs were exposed to dehydrating conditions, AT(1) receptor mRNA significantly increased in the diencephalon and the rhombencephalon. These data suggest that central Ang II may control water intake behavior via an AT(1) receptor on the diencephalon and rhombencephalon in anuran amphibians and may have implications for water consumption in vertebrates.
血管紧张素 II（Ang II）除了无尾两栖类外，会引起所有陆生脊椎动物口渴，从而刺激口服水摄入。无尾两栖类动物不通过口腔饮水，但通过腹部皮肤渗透吸收水分。在这项研究中，我们研究了血管紧张素 II 对日本树蛙（Hyla japonica）水吸收行为调节的作用。在完全水合的青蛙中，脑室内（ICV）和淋巴囊内（ILS）注射血管紧张素 II 以剂量依赖的方式显著延长水的停留时间。血管紧张素 II 依赖性水摄取被脑室内预处理的血管紧张素 II 型 1（AT（1））受体拮抗剂抑制，但不是血管紧张素 II 型 2（AT（2））受体拮抗剂。这些结果表明，血管紧张素 II 通过类似 AT（1）但不是 AT（2）的受体刺激树蛙的水吸收行为。然后，我们从脑中克隆并鉴定了树蛙 AT（1）受体的 cDNA。树蛙 AT（1）受体 cDNA 编码一个 361 个氨基酸残基的蛋白质，与蟾蜍（Bufo marinus）AT（1）受体有 87%的同一性，并表现出血管紧张素 II 受体的功能特征。在包括大脑（特别是间脑）、肺、大肠、肾脏和腹部皮肤在内的多种组织中均发现 AT（1）受体 mRNAs 存在。当树蛙暴露于脱水条件时，间脑和延髓中的 AT（1）受体 mRNA 显著增加。这些数据表明，中枢血管紧张素 II 可能通过间脑和延髓中的 AT（1）受体控制无尾两栖类动物的水摄入行为，并且可能对脊椎动物的水消耗具有意义。
