Stimulatory effect of Coca-Cola^TM on gastroduodenal HCO ⁻₃ secretion in rats

Abstract.

We examined the effect of various carbonated beverages, especially Coca-Cola^TM, on the HCO ⁻₃ secretion in the rat stomach and duodenum. Under urethane anaesthesia, a chambered stomach or a proximal duodenal loop was perfused with saline, and HCO ⁻₃ secretion was measured at pH 7.0 using a pH-stat method and by adding 2 mM HCl. The amount of CO₂ contained in these beverages was about 4–7 g/mL. Coca-Cola^TM topically applied to the mucosa for 10 min significantly increased the HCO ⁻₃ secretion in both the stomach and the duodenum. The HCO ⁻₃ response in the duodenum was totally abolished by indomethacin and also partially inhibited by acetazolamide, an inhibitor of carbonic anhydrase. Likewise, the response in the stomach was also markedly inhibited by either acetazolamide or indomethacin. The mucosal application of Coca-Cola^TM increased the PGE₂ contents in both the stomach and the duodenum. Other carbonated beverages, such as sparkling water, Fanta Grape^TM or cider, also increased the HCO ⁻₃ secretion in these tissues. These results suggest that Coca-Cola^TM induces HCO ⁻₃ secretion in both the stomach and the duodenum, and these responses may be attributable to both the intracellular supply of HCO ⁻₃ generated via carbonic anhydrase, and endogenous PGs, probably related to the acidic pH of the solution.