Vilella S, Zonno V, Lapadula M, Verri T, Storelli C
Dipartimento di Biologia, Università di Lecce, Italy.
J Exp Zool. 1995 Jan 1;271(1):18-26. doi: 10.1002/jez.1402710103.
The ability of eel intestinal epithelial cells to recover from an acute acid load was analysed using the fluorescent dye 2',7'-bis-carboxy-ethyl-5,6-carboxyfluorescein (BCECF) and cell suspensions. Under these experimental conditions (bicarbonate-free solutions) the resting pHi in cells prepared from sea-water (7.52 +/- 0.031) and fresh-water (7.50 +/- 0.094) adapted animals proved to be similar. The recovery rate (following an acid load) increases by increasing the Na ion concentration in the extracellular medium. This pHi recovery is competitively inhibited by the specific inhibitor dimethylamiloride (DMA) with a low Ki in sea- (1.2 microM) as well as in fresh-water (1.3 microM) adapted animals, indicating the presence of a specific Na/H exchange activity in these cells. Using basolateral membrane vesicles it could be demonstrated that this activity is located on the basolateral side of the enterocyte membrane. The kinetic parameters (Kapp and Jmax) of this exchanger are similar in fresh-water and sea-water adapted animals suggesting that no salinity adaptation occurs, thus excluding the involvement of the antiporter in the osmoregulatory processes. These results are in agreement with the presence in the plasma membrane of the eel enterocytes of a Na/H-1 (housekeeper) form of the antiporter.
使用荧光染料2',7'-双羧乙基-5,6-羧基荧光素（BCECF）和细胞悬液分析了鳗鱼肠上皮细胞从急性酸负荷中恢复的能力。在这些实验条件下（无碳酸氢盐溶液），从适应海水（7.52±0.031）和淡水（7.50±0.094）的动物制备的细胞中的静息细胞内pH值被证明是相似的。（酸负荷后）恢复率通过增加细胞外培养基中的钠离子浓度而提高。这种细胞内pH值的恢复受到特异性抑制剂二甲基amiloride（DMA）的竞争性抑制，在适应海水（1.2微摩尔）和淡水（1.3微摩尔）的动物中其Ki值较低，表明这些细胞中存在特异性的钠/氢交换活性。使用基底外侧膜囊泡可以证明这种活性位于肠细胞膜的基底外侧。这种交换体的动力学参数（Kapp和Jmax）在适应淡水和海水的动物中相似，这表明没有发生盐度适应，因此排除了反向转运体参与渗透调节过程。这些结果与鳗鱼肠细胞质膜中存在钠/氢-1（管家）形式的反向转运体一致。
