Murer H, Hopfer U, Kinne R
Biochem J. 1976 Mar 15;154(3):597-604.
Studies on proton and Na+ transport by isolated intestinal and renal brush-border-membrane vesicles were carried out to test for the presence of an Na+/H+-exchange system. Proton transport was evaluated as proton transfer from the intravesicular space to the incubation medium by monitoring pH changes in the membrane suspension induced by sudden addition of cations. Na+ transport was determined as Na+ uptake into the vesicles by filtration technique. A sudden addition of sodium salts (but not choline) to the membrane suspension provokes an acidification of the incubation medium which is abolished by the addition of 0.5% Triton X-100. Pretreatment of the membranes with Triton X-100 prevents the acidification. The acidification is also not observed if the [K+] and proton conductance of the membranes have been increased by the simultaneous addition of valinomycin and carbonyl cyanide p-trifluoromethoxyphenylhydrazone to the K+-rich incubation medium. Either valinomycin or carbonyl cyanide p-trifluoromethoxyphenylhydrazone when added alone do not alter the response of the membranes to the addition of Na+. Na+ uptake by brush-border microvilli is enhanced in the presence of a proton gradient directed from the intravesicular space to the incubation medium. Under these conditions a transient accumulation of Na+ inside the vesicles is observed. It is concluded that intestinal and renal brush-border membranes contain a NA+/H+ antiport system which catalyses an electroneutral exchange of Na+ against protons and consequently can produce a proton gradient in the presence of a concentration difference for Na+. This system might be involved in the active proton secretion of the small intestine and the proximal tubule of the kidney.
开展了关于分离的肠和肾刷状缘膜囊泡中质子和Na⁺转运的研究，以检测Na⁺/H⁺交换系统的存在。通过监测阳离子突然添加引起的膜悬浮液pH变化，将质子转运评估为质子从囊泡内空间转移到孵育介质中。通过过滤技术将Na⁺转运确定为Na⁺摄取到囊泡中。向膜悬浮液中突然添加钠盐（而非胆碱）会引发孵育介质酸化，添加0.5% Triton X-100可消除这种酸化。用Triton X-100预处理膜可防止酸化。如果通过向富含K⁺的孵育介质中同时添加缬氨霉素和羰基氰对三氟甲氧基苯腙来增加膜的[K⁺]和质子传导性，也不会观察到酸化现象。单独添加缬氨霉素或羰基氰对三氟甲氧基苯腙均不会改变膜对添加Na⁺的反应。在存在从囊泡内空间指向孵育介质的质子梯度时，刷状缘微绒毛对Na⁺的摄取会增强。在这些条件下，观察到囊泡内Na⁺的短暂积累。得出的结论是，肠和肾刷状缘膜含有一种Na⁺/H⁺反向转运系统，该系统催化Na⁺与质子的电中性交换，因此在存在Na⁺浓度差的情况下可产生质子梯度。该系统可能参与小肠和肾近端小管的主动质子分泌。
