Kirchhoff Philipp, Wagner Carsten A, Gaetzschmann Florian, Radebold Klaus, Geibel John P
Department of Surgery, Yale University School of Medicine, New Haven, Connecticut 06511, USA.
Am J Physiol Gastrointest Liver Physiol. 2003 Dec;285(6):G1242-8. doi: 10.1152/ajpgi.00165.2003. Epub 2003 Aug 7.
Previous studies have shown that gastric glands express at least sodium-hydrogen exchanger (NHE) isoforms 1-4. Our aim was to study NHE-3 localization in rat parietal cells and to investigate the functional activity of an apical membrane NHE-3 isoform in parietal cells of rats. Western blot analysis and immunohistochemistry showed expression of NHE-3 in rat stomach colocalizing the protein in parietal cells together with the beta-subunit of the H(+)-K(+)-ATPase. Functional studies in luminally perfused gastric glands demonstrated the presence of an apical NHE isoform sensitive to low concentrations of 5-ethylisopropyl amiloride (EIPA). Intracellular pH measurements in parietal cells conducted in omeprazole-pretreated superfused gastric glands showed an Na+-dependent proton extrusion pathway that was inhibited both by low concentrations of EIPA and by the NHE-3 specific inhibitor S3226. This pathway for proton extrusion had a higher activity in resting glands and was inhibited on stimulation of histamine-induced H(+)-K(+)-ATPase proton extrusion. We conclude that the NHE-3 isoform located on the apical membrane of parietal cells offers an additional pathway for proton secretion under resting conditions. Furthermore, the gastric NHE-3 appears to work under resting conditions and inactivates during periods of H(+)-K(+)-ATPase activity.
以往研究表明，胃腺至少表达钠氢交换体（NHE）同工型1 - 4。我们的目的是研究NHE - 3在大鼠壁细胞中的定位，并探讨顶膜NHE - 3同工型在大鼠壁细胞中的功能活性。蛋白质印迹分析和免疫组织化学显示，NHE - 3在大鼠胃中表达，该蛋白与H(+) - K(+) - ATP酶的β亚基共同定位于壁细胞中。对经腔内灌注的胃腺进行的功能研究表明，存在一种对低浓度5 - 乙基异丙基氨氯吡脒（EIPA）敏感的顶膜NHE同工型。在经奥美拉唑预处理的灌流胃腺中对壁细胞进行的细胞内pH测量显示，存在一条依赖Na+的质子外排途径，该途径受到低浓度EIPA和NHE - 3特异性抑制剂S3226的抑制。这条质子外排途径在静息腺中具有较高活性，在组胺诱导的H(+) - K(+) - ATP酶质子外排刺激时受到抑制。我们得出结论，位于壁细胞顶膜的NHE - 3同工型在静息条件下为质子分泌提供了一条额外途径。此外，胃NHE - 3似乎在静息条件下起作用，在H(+) - K(+) - ATP酶活性期间失活。
