High-resolution immunogold cytochemistry indicates that AQP4 is concentrated along the basal membrane of parietal cell in rat stomach

Gastric parietal cells secrete hydrochloric acid in stomach. Because the se creted HCl solution is isotonic with the plasma fluid, it should accompany the water transport across the membranes of parietal cells. Aquaporins (AQP s) are water channel proteins that play the central role in the cellular ha ndling of water in various mammalian tissues. Using immunocytochemistry, we found that AQP4 was expressed only in parietal cells of rat gastric mucose , Immunogold electron microscopy study further demonstrated that AQP4 was m ostly localized at the basal membrane of parietal cells. In the basal membr ane, AQP4 was prominently enriched on the portion contacting with the basem ent membrane surrounding gastric glands. These results suggest that the con tact between basement membrane and basal membrane may generate the signal i nvolved in the targeting of AQP4 in gastric parietal cells. (C) 1999 Federa tion of European Biochemical Societies.