生活在不同环境中的青蛙肾脏的肾单位结构以及离子泵和水通道蛋白的免疫组织化学定位。

Uchiyama M, Yoshizawa H

Department of Biology, Faculty of Science, Toyama University, Gofuku 3190, Toyama 930-8555, Japan.

Symp Soc Exp Biol. 2002(54):109-28.

Amphibians inhabit areas ranging from completely aqueous to terrestrial environments and move between water and land. The kidneys of all anurans are similar at the gross morphological level: the structure of their nephrons is related to habitat. According to the observation by light and electron microscopy, the cells that make up the nephron differ among species. Immunohistochemical studies using antibodies to various ATPases showed a significant species difference depending on habitat. The immunoreactivity for Na+,K(+)-ATPase was low in the proximal tubules but high in the basolateral membranes of early distal tubules to collecting ducts in all species. In the proximal tubule, apical membranes of the cells were slightly immunoreactive to H(+)-ATPase antibody in aquatic species. In the connecting tubule and the collecting duct, the apical membrane of intercalated cells was immunoreactive in all species. In aquatic species, H+,K(+)-ATPase immunoreactivity was observed in cell along the proximal, distal tubule to the collecting duct. However, H+,K(+)-ATPase was present along the intercalated cells of the distal segments from early distal to collecting tubules in terrestrial and semi-aquatic species. In the renal corpuscle, the neck segment and the intermediate segment, immunoreactivities to ion pumps were not observed in any of the species examined. Taking together our observations, we conclude that in the aquatic species, a large volume of plasma must be filtered in a large glomerulus and the ultrafiltrate components are reabsorbed along a large and long proximal segment of the nephron. Control of tubular transport may be poorly developed when a small short distal segment of the nephron is observed. On the contrary, terrestrial species have a long and well-developed distal segment and regulation mechanisms of tubular transport may have evolved in these segments. Thus, the development of the late distal segments of the nephron is one of the important factors for the terrestrial adaptation.

两栖动物栖息于从完全水生到陆地的各种环境中，并在水和陆地之间移动。所有无尾两栖类动物的肾脏在大体形态水平上相似：其肾单位的结构与栖息地有关。根据光镜和电镜观察，构成肾单位的细胞在不同物种间存在差异。使用针对各种ATP酶的抗体进行的免疫组织化学研究表明，根据栖息地不同存在显著的物种差异。在所有物种中，近端小管对Na⁺,K⁺-ATP酶的免疫反应性较低，但在早期远端小管至集合管的基底外侧膜中较高。在近端小管中，水生物种细胞的顶端膜对H⁺-ATP酶抗体有轻微免疫反应。在连接小管和集合管中，所有物种的闰细胞顶端膜都有免疫反应。在水生物种中，从近端小管、远端小管到集合管的细胞中都观察到H⁺,K⁺-ATP酶免疫反应性。然而，在陆生和半水生物种中，从早期远端小管到集合小管的远端节段的闰细胞中都存在H⁺,K⁺-ATP酶。在肾小体、颈部节段和中间节段中，在所检查的任何物种中都未观察到对离子泵的免疫反应性。综合我们的观察结果，我们得出结论，在水生物种中，必须在大肾小球中过滤大量血浆，超滤液成分在肾单位的大且长的近端节段中被重吸收。当观察到肾单位的短而小的远端节段时，肾小管转运的控制可能发育不良。相反，陆生物种有长且发育良好的远端节段，肾小管转运的调节机制可能在这些节段中进化。因此，肾单位远端晚期节段的发育是陆地适应性的重要因素之一。