Vacuolar-type proton pump in the basolateral plasma membrane energizes ion uptake in branchial mitochondria-rich cells of killifish Fundulus heteroclitus, adapted to a low ion environment
Vacuolar-type proton pump in the basolateral plasma membrane energizes ion uptake in branchial mitochondria-rich cells of killifish Fundulus heteroclitus, adapted to a low ion environment
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DOI：
10.1242/jeb.00159
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发表时间：
2003-03-01
影响因子：
2.8
通讯作者：
Kaneko, T
中科院分区：
文献类型：
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作者：
Katoh, F;Hyodo, S;Kaneko, T
我们通过对 MR 细胞的形态学观察和液泡型质子泵 (V-ATPase) 的分子鉴定，研究了富含线粒体 (MR) 细胞在淡水适应鳉鱼 Fundulusheterectitus 中通过鳃上皮细胞吸收离子的情况。比较了适应不同 NaCl 浓度的特定淡水的鱼的 MR 细胞形态：低 (0.1 mmol l(-1))-、中 (1 mmol l(-1))-和高 (10 mmol l(-1))-NaCl 环境。 MR细胞主要位于鳃丝的传入血管侧，在低和中氯化钠环境中比在高氯化钠环境中更大。电镜观察显示，在低和中氯化钠环境中，发育良好的MR细胞的顶膜平坦或略微突出，并配备有微绒毛以扩大暴露于这些环境的表面积。另一方面，在高NaCl环境中，尽管NaCl浓度远低于血浆中的浓度，但顶膜内陷形成凹坑，MR细胞常与辅助细胞形成多细胞复合物。我们克隆并测序了编码鳉鱼 V-ATP 酶 A 亚基的 cDNA。推导的氨基酸序列与其他脊椎动物物种的 V-ATP 酶 A 亚基具有高度同一性。使用同源抗体的光学显微镜免疫细胞化学显示，在低 NaCl 淡水中，Na+/K+-ATPase 免疫反应性 MR 细胞具有 V-ATPase 免疫反应性，而在高 NaCl 环境中，免疫反应性要弱得多。此外，免疫电镜显示 V-ATPase 位于 MR 细胞的基底外侧膜中。这些发现表明，MR 细胞是适应淡水的鳉鱼中负责活性离子吸收的位点，并且位于基底外侧的 V-ATP 酶参与 MR 细胞的 Na+ 和/或 Cl- 吸收机制。
We examined the involvement of mitochondria-rich (MR) cells in ion uptake through gill epithelia in freshwater-adapted killifish Fundulus heteroctitus, by morphological observation of MR cells and molecular identification of the vacuolar-type proton pump (V-ATPase). MR cell morphology was compared in fish acclimated to defined freshwaters with different NaCl concentrations: low (0.1 mmol l(-1))-, mid (1 mmol l(-1))- and high (10 mmol l(-1))-NaCl environments. MR cells, mostly located on the afferent-vascular side of the gill filaments, were larger in low- and mid-NaCl environments than in the high-NaCl environment. Electron-microscopic observation revealed that the apical membrane of well-developed MR cells in low- and mid-NaCl environments was flat or slightly projecting, and equipped with microvilli to expand the surface area exposed to these environments. On the other hand, in the high-NaCl environment, the apical membrane was invaginated to form a pit, and MR cells often formed multicellular complexes with accessory cells, although the NaCl concentration was much lower than that in plasma. We cloned and sequenced a cDNA encoding the A-subunit of killifish V-ATPase. The deduced amino acid sequence showed high identity with V-ATPase A-subunits from other vertebrate species. Light-microscopic immunocytochemistry, using a homologous antibody, revealed V-ATPase-immunoreactivity in Na+/K+-ATPase-immunoreactive MR cells in low-NaCl freshwater, whereas the immunoreactivity was much weaker in higher NaCl environments. Furthermore, immuno-electron microscopy revealed V-ATPase to be located in the basolateral membrane of MR cells. These findings indicate that MR cells are the site responsible for active ion uptake in freshwater-adapted killifish, and that basolaterally located V-ATPase is involved in the Na+ and/or Cl- absorbing mechanism of MR cells.