Stuart-Tilley A, Sardet C, Pouyssegur J, Schwartz M A, Brown D, Alper S L
Molecular Medicine Unit, Beth Israel Hospital, Boston 02215.
Am J Physiol. 1994 Feb;266(2 Pt 1):C559-68. doi: 10.1152/ajpcell.1994.266.2.C559.
The gastric mucosa secretes both protons and bicarbonate. The molecular identity of the H(+)-K(+)-ATPase, which mediates acid secretion, has long been known, but the other components of the secretory machinery and their cellular disposition are less well characterized. This study identifies and localizes in rat and rabbit gastric mucosa a chloride-bicarbonate exchanger protein and a Na(+)-H+ exchanger protein. The previously described band 3-related protein of the parietal cell has been identified by isoform-specific antibodies as anion exchanger (AE) 2 and localized to the basolateral membranes of the parietal cells. The Na(+)-H+ exchanger protein NHE-1 was located in the basolateral membranes of the mucous neck cells, interdigitated between the parietal cells of the gastric glands and in the basolateral membranes of the surface mucous cells. Neither transporter protein was abundantly expressed deep in the gland, where most of the pepsinogen cells reside. Carbonic anhydrase II (CA II) was expressed at higher abundance in the surface mucous cells and mucous neck cells, which expressed NHE-1, than in the parietal cells, which expressed AE2. The morphological evidence identified AE2 as a major parietal cell anion exchanger, whereas NHE-1 and CA II colocalized in mucous neck, chief, and surface mucous cells. We propose that all three of these cell types contribute to gastric bicarbonate secretion.
胃黏膜会分泌质子和碳酸氢盐。介导胃酸分泌的H(+)-K(+)-ATP酶的分子特性早已为人所知，但分泌机制的其他成分及其细胞定位却鲜为人知。本研究在大鼠和兔的胃黏膜中鉴定并定位了一种氯-碳酸氢盐交换蛋白和一种钠-氢交换蛋白。壁细胞中先前描述的与带3相关的蛋白已通过同工型特异性抗体鉴定为阴离子交换蛋白（AE）2，并定位于壁细胞的基底外侧膜。钠-氢交换蛋白NHE-1位于黏液颈细胞的基底外侧膜，在胃腺壁细胞之间相互交错，并存在于表面黏液细胞的基底外侧膜。这两种转运蛋白在胃蛋白酶原细胞所在的腺深部均未大量表达。碳酸酐酶II（CA II）在表达NHE-1的表面黏液细胞和黏液颈细胞中的表达丰度高于表达AE2的壁细胞。形态学证据表明AE2是主要的壁细胞阴离子交换蛋白，而NHE-1和CA II共定位于黏液颈细胞、主细胞和表面黏液细胞中。我们认为这三种细胞类型均有助于胃碳酸氢盐的分泌。
