Stimulation by sparkling water of gastroduodenal HCO3- secretion in rats

Background: We examined the effect of sparkling water on gastroduodenal HCO 3 - secretion in rats and investigated the factors involved in these responses. Material/Methods: Under urethane anesthesia, a chambered stomach or a proximal duodenal loop was superfused with saline, and HCO 3 - secretion was measured at pH 7.0 using a pH-stat. Results: The amount of CO 2 in sparkling water was about 7.2 g/L. The mucosal exposure with sparkling water increased the secretion of HCO 3 - in both the stomach and duodenum. The HCO 3 - response in the duodenum was partially inhibited by indomethacin, acetazolamide or sensory deafferentation and was totally abolished by the co-administration of the former two agents. By contrast, the response in the stomach was almost totally inhibited by acetazolamide and partially mitigated by indomethacin but not sensory deafferentation. DIDS [an inhibitor of the CL - /HCO 3 - exchanger (AE) and the Na + -HCO 3 - cotransporter (NBC)] and DMA [an inhibitor of the Na + /H + exchanger 1 (NHE1)] partially mitigated the HCO 3 - response in the duodenum but not the stomach. The mucosal application of sparkling water increased prostaglandin E 2 content in these tissues. Conclusions: Sparkling water stimulates HCO 3 - secretion in both the stomach and the duodenum, but the mechanisms involved differ in these two tissues; the response in the former is mainly due to the intracellular supply of HCO 3 - with the aid of carbonic anhydrase, while in the latter the response is dependent on the NHE1, AE and NBC, and is mediated by endogenous prostaglandins as well as capsaicin-sensitive afferent neurons, in addition to the intracellular supply of HCO 3 - .