A New Explanation for the Osmotic Activity and Ionic Composition of Gastric Juice

¹ From the Departments of Physiology and Chemistry, University of Louisville, Louisville, Kentucky

In an attempt to extend a previously proposed theory of gastric HCl production, the possibility is considered that the surface epithelial cells secrete H⁺ ions and the parietal cells Cl^– ions and water. It is postulated that water is transported as a result of its chemical potential gradient between the interstitial fluid and the canalicular lumen of the parietal cells. It is shown that this scheme can quantitatively explain, without further postulates, the high normalities of secretion found in the glycine experiments of Teorell. However, the scheme predicts for pure gastric juice a higher osmotic pressure than that found. Furthermore, the scheme does not offer an explanation for the presence of the other inorganic ions of gastric juice. In an attempt to account for the observed osmotic pressure and the inorganic ion content of gastric juice, the implications are developed of the assumption that the Na⁺ ions, K⁺ ions and some of the secreted Cl^– ions are transported across the mucosa in the direction of their electrochemical potential gradients. It is shown that the resulting scheme can account for the composition and osmotic pressure of gastric juice at least as well as any of the schemes proposed by other workers. The implications of the present scheme with respect to the problem of the production of hypertonic and hypotonic secretions are discussed.