26 Pages

Gastroduodenal Bicarbonate Secretion — Pharmacological Modulation and Contribution to Mucosal Protection

ByKoji Takeuchi, Susumu Okabe

This chapter reviews the pharmacological modulation of gastroduodenal HCO3- secretion, mainly based upon data obtained using the rat in vivo. It describes the contribution of this secretion to mucosal protection, and introduces various experimental duodenal ulcers that occur in association with the impairment of HCO3- secretion. Bicarbonate secretion has been demonstrated in vivo using both the stomach and duodenum of various mammals such as the guinea pig, rat, and dog under either conscious or anesthetized conditions. The gastroduodenal mucosa is kept intact by multiple protective mechanisms, despite exposure to acid and other chemical harzards. Bicarbonate secretion is one of these mechanisms, and it plays an important role in the protection of the mucosa against acid. Stress, either physical or psychological, is an important mediator of peptic ulcer diseases. Under stressful conditions, the neuronal activity of the sympathetic as well as the parasympathetic nerves are increased, leading to an increase of acid secretion and a decrease in mucosal blood flow.