The effects of applied pressure on secretion by isolated amphibian gastric mucosa

Abstract

The rates of fluid secretion and of respiration by isolated gastric mucosa were studied in an apparatus consisting of a constant pressure manometer, a modified Warburg cup and a stopper with a graduated capillary side tube. External pressure was applied to the mucosa either kept constant or varied at will. Secretion occurred against opposing pressures of at least 120 mm. Brodie soln., and was, within the limits of 50 mm. Brodie soln., independent of the magnitude and direction of the applied pressures. Neutral red was transported across the mucosa against such pressures. On stimulation with 5 x 10-5 [image] histamine the rates of secretion and of respiration increased concomitantly. In anaerobic expts. neutral fluid was forced across the mucosa in the direction of the applied pressure. This did not occur with nonsecreting mucosae under aerobic conditions. Thiocyanate (10-2 [image]) did not affect the basal QO2 or the increase of the QO2 which followed stimulation by 5 x 10-5 [image] histamine, but strongly inhibited the rate of HC1 secretion. Thiocyanate often caused passage of water across the mucosa in the direction of the external pressure for up to 1 hr. before secretion of acid and liquid was resumed at lower but steady rates. Apparently the energy for the movement of water across acid-secreting gastric mucosa is derived not from the difference in hydrostatic pressure between the blood and the gastric lumen, but from the aerobic metabolism of the oxyntic cells.