Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka 422-8529, Japan.
Endocrinology. 2010 Jan;151(1):165-73. doi: 10.1210/en.2009-0841. Epub 2009 Oct 23.
Most adult anuran amphibians except for the aquatic species absorb water across the ventral pelvic skin and reabsorb it from urine in the urinary bladder. Many terrestrial and arboreal species use a region in the posterior or pelvic region of the ventral skin that is specialized for rapid rehydration from shallow water sources or moist substrates. Periods of terrestrial activity can be prolonged by reabsorption of dilute urine from the urinary bladder. Aquaporin (AQP), a water channel protein, plays a fundamental role in these water absorption/reabsorption processes, which are regulated by antidiuretic hormone. Characterization of AQPs from various anurans revealed that the unique water homeostasis is basically mediated by two types of anuran-specific AQPs, i.e. ventral pelvic skin and urinary bladder type, respectively. The bladder-type AQP is further expressed in the pelvic skin of terrestrial and arboreal species, together with the pelvic skin-type AQP. In contrast, the pelvic skin-type AQP (AQP-x3) of the aquatic Xenopus has lost the ability of efficient protein production. The extra C-terminal tail in AQP-x3 consisting of 33 nucleotides within the coding region appears to participate in the posttranscriptional regulation of AQP-x3 gene expression by attenuating protein expression. The positive transcriptional regulation of bladder-type AQP in the pelvic skin and negative posttranscriptional regulation of pelvic skin-type AQP provide flexibility in the water regulation mechanisms, which might have contributed to the evolutionary adaptation of anurans to a wide variety of water environments.
除水生物种外，大多数成年蛙类通过腹侧骨盆皮肤吸收水分，并从膀胱中的尿液中重新吸收水分。许多陆生和树栖物种使用腹侧皮肤后部或骨盆区域的专门区域，从浅水来源或潮湿基质中快速重新吸收水分。通过从膀胱中重新吸收稀释的尿液，可以延长陆地活动的时间。水通道蛋白（AQP）是一种水通道蛋白，在这些水吸收/再吸收过程中起基本作用，这些过程受抗利尿激素调节。从各种蛙类中鉴定的 AQP 表明，独特的水稳态基本上是由两种类型的蛙类特异性 AQP 介导的，即腹侧骨盆皮肤型和膀胱型。膀胱型 AQP 进一步在陆生和树栖物种的骨盆皮肤中表达，与骨盆皮肤型 AQP 一起表达。相比之下，水生非洲爪蟾的骨盆皮肤型 AQP（AQP-x3）失去了有效蛋白质生产的能力。编码区域内包含 33 个核苷酸的 AQP-x3 额外的 C 末端尾巴似乎通过削弱蛋白质表达参与 AQP-x3 基因表达的转录后调节。膀胱型 AQP 在骨盆皮肤中的正向转录调节和骨盆皮肤型 AQP 的负转录后调节为水调节机制提供了灵活性，这可能有助于蛙类对各种水环境的进化适应。
