Na+-H+ exchange in rat colonic brush-border membrane vesicles.
Na+-H+ exchange in rat colonic brush-border membrane vesicles.
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大鼠结肠刷状缘膜囊泡中的 Na-H 交换。
DOI：
10.1152/ajpgi.1986.250.6.g781
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Brasitus,TA
中科院分区：
文献类型：
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作者：
Foster,ES;Dudeja,PK;Brasitus,TA
为了证明大鼠结肠细胞刷状缘膜囊泡中存在Na+-H+交换过程，我们用吖啶橙的荧光响应来监测pH梯度的形成和消散。向内的Na+梯度刺激了H+的向外流动，而质子的内流则受到向外的Na+梯度的刺激。由于离子载体在K+梯度存在的情况下不改变Na+刺激的质子外流，Na+和H+运动的相互关系不能仅仅基于膜电位来解释。Na+刺激的质子外流是饱和的，Na+的Km为20.1+/-1.6 mm。向内定向的Li+梯度也刺激了质子的外流，Li+的Km为30.2+/-1.7 mm。相反，不适当的阳离子不能刺激H+向外流动。阿米洛利(1 MM)对Na+刺激的质子外流和内流均有抑制作用。因此，在大鼠结肠刷状缘膜上存在Na+-H+交换，并具有与其他Na+-H+逆向转运蛋白相似的特征。这种交换过程可能是大肠吸收Na+的一个重要机制。
To demonstrate the presence of a Na+-H+ exchange process in brush-border membrane vesicles from rat colonocytes, the fluorescence response of acridine orange was used to monitor the formation and dissipation of pH gradients. An inwardly directed Na+ gradient stimulated the outward flux of H+, whereas proton influx was stimulated by an outwardly directed Na+ gradient. Since the ionophore valinomycin in the presence of a K+ gradient did not alter Na+-stimulated proton efflux, the interrelationship of Na+ and H+ movement could not be explained solely on the basis of a membrane potential. Na+-stimulated proton efflux was saturable with a Km for Na+ of 20.1 +/- 1.6 mM. Inwardly directed Li+ gradients also stimulated proton efflux, and the Km for Li+ was 30.2 +/- 1.7 mM. In contrast, impermeant cations failed to stimulate the outward flux of H+. Amiloride (1 mM) inhibited both Na+-stimulated proton efflux and influx. Therefore, Na+-H+ exchange is present in rat colonic brush-border membranes and has characteristics similar to other Na+-H+ antiporters. This exchange process may be an important mechanism for Na+ absorption in the large intestine.