Contribution of Cl(-)-OH- exchange to electroneutral NaCl absorption in rat distal colon.
Contribution of Cl(-)-OH- exchange to electroneutral NaCl absorption in rat distal colon.
复制标题
Cl(-)-OH-交换对大鼠远端结肠电中性 NaCl 吸收的贡献。
DOI：
10.1152/ajpgi.1990.258.2.g261
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Brasitus,TA
中科院分区：
文献类型：
--
作者：
Foster,ES;Dudeja,PK;Brasitus,TA
中性NaCl吸收是大鼠远端结肠Na+吸收的主要过程。这种中性NaCl吸收过程是Na（+）-Cl-共转运还是Na（+）-H+和Cl（-）-OH-的双重离子交换尚不确定。最近使用大鼠结肠刷状缘膜囊泡（BBMV）的研究描述了Na（+）-H+交换机制，并提出通过双离子交换过程发生净NaCl吸收。然而，迄今为止，结肠顶端膜上的阴离子交换剂尚未被确定。为了确定是否存在Cl（-）-OH-交换过程，通过大鼠远端结肠BBMV评价36 Cl摄取。pH梯度（7.7 in/5.5 out）刺激活性Cl-吸收。氯-摄取没有显着影响的存在下，缬氨霉素诱导的K+扩散电位（内正），这表明氯-传导途径是不存在于这些膜。pH梯度刺激的Cl-摄取是Cl-浓度的饱和函数，Km为14.3 +/- 5.0 mM，Vmax为20.4 +/- 5.5 nmol.mg protein-1.30 s-1，并且几乎完全被1 mM浓度的SITS和DIDS（其他上皮细胞中阴离子交换过程的抑制剂）抑制。向内梯度的Na+，K+，或Na+和K+没有进一步刺激初始的Cl-吸收，这表明耦合的Na+和Cl-运动不发生的共转运机制。因此，大鼠远端结肠BBMV中存在Cl（-）-OH-交换过程。（250字处删节）
Neutral NaCl absorption is the predominant Na+ absorptive process in rat distal colon. Whether this neutral NaCl absorptive process represents Na(+)-Cl- cotransport or dual ion exchanges of Na(+)-H+ and Cl(-)-OH- has been uncertain. Recent studies using rat colonic brush-border membrane vesicles (BBMVs) have described a Na(+)-H+ exchange mechanism and have proposed that net NaCl absorption occurs via a dual ion exchange process. To date, however, an anion exchanger on the colonic apical membrane has not been identified. To determine whether a Cl(-)-OH- exchange process is present, 36Cl uptake was evaluated across rat distal colonic BBMVs. A pH gradient (7.7 in/5.5 out) stimulated active Cl- uptake. Cl- uptake was not significantly affected by the presence of a valinomycin-induced K+ diffusion potential (inside positive), suggesting that a Cl- conductive pathway is not present in these membranes. The pH gradient-stimulated Cl- uptake was a saturable function of the Cl- concentration with a Km of 14.3 +/- 5.0 mM and a Vmax of 20.4 +/- 5.5 nmol.mg protein-1.30 s-1 and was almost completely inhibited by 1 mM concentrations of SITS and DIDS, inhibitors of anion exchange processes in other epithelia. Inward gradients of Na+, K+, or Na+ and K+ did not further stimulate initial Cl- uptake, suggesting that coupling of Na+ and Cl- movement does not occur by a cotransport mechanism. Thus a Cl(-)-OH- exchange process is present in rat distal colonic BBMVs.(ABSTRACT TRUNCATED AT 250 WORDS)