De Giorgi A, Carnimeo L, Corcelli A
Istituto di Fisiologia Generale, Università degli Studi, Bari, Italy.
Pflugers Arch. 1992 Apr;420(5-6):551-8. doi: 10.1007/BF00374632.
Cl- transport was studied in a preparation of brush-border membrane vesicles (BBMV) from seawater eel intestine. 36Cl- uptake appeared to be stimulated by a positive inside membrane diffusion potential generated (a) by a concentration gradient of salts, the cations of which are more permeable than the anions, (b) by a K+ diffusion potential obtained by imposing a K+ concentration gradient (Cout greater than Cin) in the presence of valinomycin, (c) an inwardly directed H+ ion concentration gradient. The membrane-potential-driven Cl- transport was inhibited by 1 mM 5-nitro-2-(4-phenylpropyl-amino)-benzoic acid. Arachidonic acid also inhibited Cl- uptake in eel intestinal BBMV, but the effect appeared to be unspecific, as the unsaturated fatty acid also affected the Na+ dependent D-glucose uptake. The effect of arachidonic acid was reversed in the presence of bovine serum albumin. Cl- influx was the same in the presence of inwardly directed gradients of Li+, Na+ or K+, arguing against the presence of Na(+)-Cl-, as well as K(+)-Cl- cotransport. The absence of a significant contribution of the Na(+)-K(+)-2Cl- cotransport mechanism to the Cl- uptake in seawater eel intestinal BBMV was indicated from the observations that Cl- uptake was not stimulated by the simultaneous presence of inwardly directed Na+ and K+ gradients, and that it was nearly insensitive to 1 mM bumetanide in the presence of extravesicular Na+ and K+. Furthermore, no evidence for the dependence of Cl- uptake on the Na+ gradient was obtained under a short-circuited membrane diffusion potential, i.e. in the presence of equilibrated K+ and valinomycin.(ABSTRACT TRUNCATED AT 250 WORDS)
在海鳗肠道刷状缘膜囊泡（BBMV）制剂中研究了氯离子（Cl⁻）转运。36Cl⁻摄取似乎受到以下因素产生的膜内正扩散电位的刺激：（a）盐浓度梯度，其中阳离子比阴离子更易通透；（b）在缬氨霉素存在下通过施加钾离子浓度梯度（胞外大于胞内）获得的钾离子扩散电位；（c）内向的氢离子浓度梯度。膜电位驱动的Cl⁻转运受到1 mM 5-硝基-2-（4-苯丙基氨基）苯甲酸的抑制。花生四烯酸也抑制海鳗肠道BBMV中的Cl⁻摄取，但这种作用似乎是非特异性的，因为这种不饱和脂肪酸也影响钠离子依赖性D-葡萄糖摄取。在牛血清白蛋白存在下，花生四烯酸的作用被逆转。在存在内向的锂离子、钠离子或钾离子梯度时，Cl⁻内流相同，这与存在钠离子-氯离子以及钾离子-氯离子共转运的观点相悖。观察结果表明，在同时存在内向的钠离子和钾离子梯度时，Cl⁻摄取未受到刺激，并且在胞外存在钠离子和钾离子的情况下，它对1 mM布美他尼几乎不敏感，这表明在海鳗肠道BBMV中，钠离子-钾离子-2氯离子共转运机制对Cl⁻摄取没有显著贡献。此外，在短路膜扩散电位下，即在存在平衡的钾离子和缬氨霉素的情况下，未获得Cl⁻摄取依赖于钠离子梯度的证据。（摘要截短于250字）
