Composition and Osmolarity of Gastric Juice as a Function of Plasma Osmolarity

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

The composition of gastric juice during the initial phases of secretion in stomachs washed with distilled water is different than in unwashed stomachs. Stomachs not secreting acid were washed with distilled water and it was found that considerably more Na⁺ ion than K⁺ ion entered the water. Intravenous hypertonic loading with 0.64 m NaCl results in a) a decrease in the volume of secretion, b) a tendency for the osmolarity of gastric juice to increase in the early phases of loading and a decline to a level lower than the normal level in the later phases of loading, c) a decrease in the ratio of the osmolarity of gastric juice to that of plasma which is associated with a simultaneous increase in the Na⁺ ion concentration and a decrease in H⁺ ion concentration of gastric juice, and d) relatively little change in the K⁺ ion concentration. Intravenous injections of 0.04 m NaCl results in a) an increase in the volume of secretion during the early phases, b) a decrease in osmolarity of the gastric juice and c) relatively little change in the Na⁺ and K⁺ ion concentrations. These data are analyzed on the basis of a previously proposed hypophysis.