Facilitated NaCl Uptake in the Highly Developed Bundle of the Nephron in Japanese Red Stingray Hemitrygon akajei Revealed by Comparative Anatomy and Molecular Mapping
Facilitated NaCl Uptake in the Highly Developed Bundle of the Nephron in Japanese Red Stingray Hemitrygon akajei Revealed by Comparative Anatomy and Molecular Mapping
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DOI：
10.2108/zs200038
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发表时间：
2020-10-01
影响因子：
0.9
通讯作者：
Hyodo, Susumu
中科院分区：
文献类型：
--
作者：
Aburatani, Naotaka;Takagi, Wataru;Hyodo, Susumu
蝙蝠总科(放射科和溜冰科)是脊椎动物的一个单系亚群，大约270 Mya的时候，它们从与Selchii(鲨鱼)的共同祖先分化而来。与鲨鱼不同的是，大量的蝙蝠可以适应低盐度的环境，鲨鱼大多是狭盐海洋物种。在弹性鳃的渗透调节器官中，已知肾脏专用于尿素在尿渗性软骨鱼中的滞留。然而，我们对蝙蝠类动物肾脏中尿素的再吸收机制知之甚少。在这里，我们对红貂鱼和两种鲨鱼的肾单位进行了生理和组织学研究。研究发现，在自然海水条件下，黄貂鱼的尿/血浆中盐分和尿素浓度的比值显著低于浑浊猫鲨(Scyliorhinus Torazame)，这表明黄貂鱼的肾脏对这些渗透物质的再吸收能力更强。通过比较黄貂鱼和斑点叉尾鲨(Triakis Scyllium)肾脏的三维图像，我们发现黄貂鱼的管束结构更为紧凑。在黄貂鱼肾脏的致密管束中，远端稀释管高度发达，并经常盘绕在近端和集合管周围。在螺旋稀释段，NKAα1(Na+/K+-ATPase)和NKCC2(Na+-K+-2Cl(-)共转运体2)mRNAs共表达显著。这些发现表明，黄貂鱼肾脏极大地促进了氯化钠的重吸收，导致了尿素的较高重吸收速率。减少肾小球滤过液中渗透压的损失可能有利于BATID对广泛的环境盐度的适应。
Batoidea (rays and skates) is a monophyletic subgroup of elasmobranchs that diverged from the common ancestor with Selachii (sharks) about 270 Mya. A larger number of batoids can adapt to low-salinity environments, in contrast to sharks, which are mostly stenohaline marine species. Among osmoregulatory organs of elasmobranchs, the kidney is known to be dedicated to urea retention in ureosmotic cartilaginous fishes. However, we know little regarding urea reabsorbing mechanisms in the kidney of batoids. Here, we performed physiological and histological investigations on the nephrons in the red stingray (Hemitrygon akajei) and two shark species. We found that the urine/plasma ratios of salt and urea concentrations in the stingray are significantly lower than those in cloudy catshark (Scyliorhinus torazame) under natural seawater, indicating that the kidney of stingray more strongly reabsorbs these osmolytes. By comparing the three-dimensional images of nephrons between stingray and banded houndshark (Triakis scyllium), we showed that the tubular bundle of stingray has a more compact configuration. In the compact tubular bundle of stingray kidney, the distal diluting tubule was highly developed and frequently coiled around the proximal and collecting tubules. Furthermore, co-expression of NKA alpha 1 (Na+/K+-ATPase) and NKCC2 (Na+-K+-2Cl(-) cotransporter 2) mRNAs was prominent in the coiled diluting segment. These findings imply that NaCl reabsorption is greatly facilitated in the stingray kidney, resulting in a higher reabsorption rate of urea. Lowering the loss of osmolytes in the glomerular filtrate is likely favorable to the adaptability of batoids to a wide range of environmental salinity.