Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6E 4W1.
Comp Biochem Physiol A Mol Integr Physiol. 2011 Jul;159(3):234-41. doi: 10.1016/j.cbpa.2011.02.025. Epub 2011 Mar 3.
The rate of acid-stimulated and phenamil-sensitive sodium (Na(+)) uptake was measured in three different cell lineages: pavement cells (PVC), total mitochondrion-rich (MR) cell populations, and peanut lectin agglutinin-negative mitochondrion-rich cells (PNA(-) MR) isolated from the rainbow trout gill epithelium. Despite the presence of basal levels of Na(+) uptake in PVC, this transport was not enhanced by acidification, nor was it inhibited by independent treatment with bafilomycin (i.e., a V-type H(+)-ATPase inhibitor), phenamil (i.e., a specific inhibitor of ENaC), or Ag (a specific inhibitor of active Na(+) transport in fish). In contrast, Na(+) uptake in PNA(-) MR cells was increased by ~220% above basal levels following acidification of near 0.4 pH units in the presence of 1.0 mM external Na(+). Acid-stimulated Na(+) transport was entirely inhibited by both phenamil and bafilomycin. Silver (Ag) and copper (Cu), which are known to interfere with active Na(+) transport in fish, were also responsible for inhibiting acid stimulated Na(+) uptake in PNA(-) MR cells, but by themselves had no effect on basal Na(+) transport. Thus, we demonstrate that Ag specifically prevented acid-stimulated Na(+) uptake in PNA(-) MR cells in a dose-dependent manner. We also demonstrate rapid (<1 min) and significant inhibition of carbonic anhydrase (CA) by Ag in PNA(-) MR cells, but not in PVC. These data lend further support to the idea of a PNA(-) MR cell type as the primary site for Na(+) uptake in the freshwater (FW) gill phenotype of rainbow trout. Moreover, these findings provide support for the importance of intracellular protons in regulating the movement of Na(+) across the apical surface of the fish gill.
测定了三种不同细胞谱系中的酸刺激和苯氟胺敏感钠（Na(+)）摄取率： pavement 细胞（PVC）、总富含线粒体（MR）细胞群体和从虹鳟鱼鳃上皮中分离的花生凝集素阴性富含线粒体细胞（PNA(-) MR）。尽管 PVC 中存在基础水平的 Na(+)摄取，但酸化并没有增强这种转运，也没有被单独用巴弗洛霉素（即 V 型 H(+)-ATP 酶抑制剂）、苯氟胺（即 ENaC 的特异性抑制剂）或 Ag（鱼类中主动 Na(+)转运的特异性抑制剂）处理所抑制。相比之下，在 1.0 mM 外部 Na(+)存在下酸化近 0.4 pH 单位后，PNA(-) MR 细胞中的 Na(+)摄取增加了约 220%。酸刺激的 Na(+)转运完全被苯氟胺和巴弗洛霉素抑制。银（Ag）和铜（Cu）已知会干扰鱼类中的主动 Na(+)转运，也会抑制 PNA(-) MR 细胞中的酸刺激 Na(+)摄取，但单独使用时对基础 Na(+)转运没有影响。因此，我们证明 Ag 以剂量依赖的方式特异性地阻止了 PNA(-) MR 细胞中的酸刺激 Na(+)摄取。我们还证明了 Ag 在 PNA(-) MR 细胞中迅速（<1 分钟）和显著抑制碳酸酐酶（CA），但在 PVC 中没有。这些数据进一步支持了 PNA(-) MR 细胞类型作为虹鳟鱼淡水（FW）鳃表型中 Na(+)摄取的主要部位的观点。此外，这些发现为细胞内质子在调节鱼类鳃顶表面 Na(+)运动中的重要性提供了支持。
