Department of Biology, University of Florida, Gainesville, FL 32611, USA.
J Exp Biol. 2011 Jul 1;214(Pt 13):2140-56. doi: 10.1242/jeb.052852.
To understand renal responses to salinity change in aquatic reptiles, we examined the structure and function of the kidney in three species of snake: a marine species with a salt gland (Laticauda semifasciata), a marine species without a salt gland (Nerodia clarkii clarkii) and a freshwater species without a salt gland (Nerodia fasciata). Both marine species maintained relatively constant plasma ions, even after acclimation to saltwater. By contrast, both plasma Cl(-) and mortality increased with salinity in the freshwater species. To investigate putative renal ion regulatory mechanisms, we examined the distribution and abundance of Na(+)/K(+)-ATPase (NKA) and the Na(+)/K(+)/2Cl(-) cotransporter (NKCC2). In all species, NKA localized to the basolateral membranes of the distal tubule and the connecting segments and collecting ducts only; there was no effect of salinity on the distribution of NKA or on the abundance of NKA mRNA in any species. NKCC2 protein was undetectable in the kidney of any of the species and there was no effect of salinity on NKCC2 mRNA abundance. We also examined the distribution and abundance of aquaporin 3 (AQP3) in the kidney of these species; although putative AQP3 localized to the basolateral membranes of the connecting segments and collecting ducts of all three species, there was no effect of salinity on the localization of the protein or the abundance of the transcript. Interestingly, we found very few differences across species, suggesting that the snake kidney may play a trivial role in limiting habitat use.
为了理解水生爬行动物对盐度变化的肾脏反应，我们检查了三种蛇的肾脏结构和功能：一种具有盐腺的海洋物种（Laticauda semifasciata）、一种没有盐腺的海洋物种（Nerodia clarkii clarkii）和一种没有盐腺的淡水物种（Nerodia fasciata）。这两种海洋物种即使在适应海水后，也能保持相对稳定的血浆离子。相比之下，在淡水物种中，血浆 Cl(-) 和死亡率都随盐度的增加而增加。为了研究潜在的肾脏离子调节机制，我们检查了 Na(+)/K(+)-ATPase (NKA) 和 Na(+)/K(+)/2Cl(-) 共转运蛋白 (NKCC2) 的分布和丰度。在所有物种中，NKA 仅定位于远端肾小管和连接段以及收集管的基底外侧膜；盐度对 NKA 的分布或任何物种中 NKA mRNA 的丰度均无影响。在这些物种的肾脏中均未检测到 NKCC2 蛋白，盐度对 NKCC2 mRNA 丰度也无影响。我们还检查了这些物种肾脏中 aquaporin 3 (AQP3) 的分布和丰度；虽然推定的 AQP3 定位于连接段和收集管的基底外侧膜，但盐度对该蛋白的定位或转录本的丰度均无影响。有趣的是，我们发现物种之间几乎没有差异，这表明蛇类的肾脏在限制栖息地利用方面可能作用不大。
