Electrolyte changes in rat stomachs following instillation of acid solutions

Abstract

An isotonic solution containing 55 mEq/liter hydrogen, 100 mEq/liter sodium, and 155 mEq/liter chloride was instilled into pylorus- and cardia-ligated stomachs of intact and vagotomized anesthetized rats for 2-hr periods. Two patterns of change were observed in the solution. In all vagotomized rats and some intact animals, there was a modest increase in volume with reduction in acidity, decrease in chloride concentration and osmolality, rise in sodium concentration, and increase in potassium concentration. In some animals with intact vagi there was a larger increase in volume, an increase in acidity, rise in chloride concentration and osmolality, fall in sodium concentration, and increase in potassium concentration. Changes are compared with those previously observed in human stomachs and differences interpreted in terms of possible persistent vagal activity in the rat. Appreciable volumes of fluid were added to the gastric contents. Net gain of sodium greatly exceeded net loss of hydrogen during most periods. Both dilution-neutralization and diffusion mechanisms may operate when there is reduction in acidity of instilled acid solutions.