The in Vitro Secretion of Acid by the Gastric Mucosa of the Frog

In 1930 Delrue (1) reported that the isolated gastric mucosa of the frog, when mounted properly in a dual-chambered bath, will secrete acid and will respond to the addition of drugs. The same author subsequently demonstrated (2) the effects of varying the ionic composition of the artificial medium on the in vitro production of acid. The theoretical importance of this approach to the study of the mechanism of acid formation by the gastric glands is apparent. However, to our knowledge, this work has never been confirmed, nor has the method been applied to the problem of acid formation. METHODS. From a pithed frog the stomach, together with a short segment of the esophagus and duodenum, was removed and washed out with isotonic saline. An incision was made along the lesser curvature through the muscularis layer and the intact mucosal layer was dissected free. The resulting tube of mucosa was cut along the lesser curvature and spread out as a flat membrane over a hole, one centimeter in diameter, made in the center of a thin Monel metal plate 4 cm. square. Another similar metal plate was placed on top of the mucosa and the two were bolted together with the mucosa held firmly between them. This assembly was then mounted between two small glass chambers shaped like CaC12 tubes. Each chamber had a hole 3 inch in diameter ground on one side. The chambers were clamped together with a modified burette clamp in such a way that the edges of the holes in the glass chambers were pressed in watertight contact with rubber gaskets which had been cemented around the holes in the metal plates. The contents of the two chambers were thus separated only by the thin layer of the gastric mucosa. One chamber with a capacity of 6 cc. was filled with 0.7 per cent NaCl solution through which air was bubbled; this solution bathed the natural secretory surface of the mucosa. The other chamber with a capacity of 15 cc. was filled with an artificial nutrient solution aerated with 95 per cent oxygen and 5 per cent carbondioxide ; this solutionbathed the side of the mucosa which had originally been in contact with the muscularis.