Expression of AQP-4 in Developing Rat Stomach: An Immunohistochemical Study

ABSTRACT

PURPOSE: AQP-4 is restricted to basolateral membranes of parietal cells located in the gastric glandular base. Whereas, there is no AQP-4 immunoreactivity in the parietal cells of isthmus/ neck region of gastric gland. Expression of AQP-4 in parietal cells might be related with the functional differentiation and maturation of parietal cells. The purpose of this study was to establish the expression of AQP-4 in differentiating parietal cells in the developing rat stomach. METHODS: Stomachs from 20-day-old fetuses, 3-, 7-, and 14-day-old pups, and adults were preserved with a periodate-lysine-paraformaldehyde solution and processed for immunohistochemical studies using rabbit polyclonal antibodies to AQP-4 or H+/-K+/-ATPase. RESULTS: In the parietal cells during development of rat stomach, AQP-4 appears first at 20 days of gestation. AQP-4 immunoreactivity is restricted to the basolateral membranes of parietal cells located in the gastric glandular base not only in adults but also in all developing ages. Whereas, there is no AQP-4 immunoreactivity in the parietal cells of isthmus/neck region in all developing ages. CONCLUSION: These results suggest that in the developing rat stomach, AQP-4 expressed only in mature parietal cells which are located in the glandular base, and act as a major water channel involved in acid secretion in rat stomach.