大鼠结肠刷状缘膜囊泡中的钠氢交换

Na+-H+ exchange in rat colonic brush-border membrane vesicles.

作者信息

Foster E S, Dudeja P K, Brasitus T A

出版信息

Am J Physiol. 1986 Jun;250(6 Pt 1):G781-7. doi: 10.1152/ajpgi.1986.250.6.G781.

DOI:10.1152/ajpgi.1986.250.6.G781

Abstract

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.

摘要

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，使用吖啶橙的荧光响应来监测pH梯度的形成和消散。内向的Na⁺梯度刺激H⁺的外向通量，而外向的Na⁺梯度刺激质子内流。由于在存在K⁺梯度的情况下离子载体缬氨霉素不会改变Na⁺刺激的质子外流，因此Na⁺和H⁺运动的相互关系不能仅基于膜电位来解释。Na⁺刺激的质子外流对Na⁺的Km为20.1±1.6 mM，呈饱和状态。内向的Li⁺梯度也刺激质子外流，Li⁺的Km为30.2±1.7 mM。相比之下，不可渗透的阳离子不能刺激H⁺的外向通量。氨氯地平（1 mM）抑制Na⁺刺激的质子外流和内流。因此，Na⁺-H⁺交换存在于大鼠结肠刷状缘膜中，并且具有与其他Na⁺-H⁺反向转运体相似的特征。这种交换过程可能是大肠中Na⁺吸收的重要机制。