Carbonic Anhydrase in the Gastric Mucosa

• Main Author: Davenport, Horace Willard
• Format: Thesis
• Language: English
• Published: 1939
• Subjects: Carbonic acid
• Online Access: https://thesis.library.caltech.edu/1421/; https://thesis.library.caltech.edu/1421/3/Davenport_hw_1939.pdf; https://resolver.caltech.edu/CaltechETD:etd-04202004-105923

Summary The evidence on the site of formation of hydrochloric acid in the gastric mucosa of mammals is reviewed. The evidence points to the participation of the parietal cells in the formation and secretion of the acid, but it is insufficient to prove that the acid is or is not formed directly in or by the parietal cells. The discovery of large amounts of carbonic anhydrase in the gastric mucosa is described. A technique of analysis for the enzyme in the gastric mucosa of cats and rats and for determining histologically the number of different kinds of cells in the material analysed is described. A strong positive correlation between the enzyme concentration and the number of parietal cells is taken as proof that carbonic anhydrase is present in the parietal cells in concentration higher than in the red blood cells. Similar evidence is given that carbonic anhydrase is present in small amounts in the cells of the surface epithelium. Evidence is also given that carbonic anhydrase may be present in small amounts in the gastric juice of cats, rats and humans. The enzyme in human gastric juice is different from that in red blood cells. The bearing of these facts on the theory of the formation of hydrochloric acid is discussed, and it is concluded that the hydration of carbon dioxide to carbonic acid and the subsequent ionization of the acid may be the means by which hydrogen ions are provided. The energy necessary for the formation of hydrochloric acid from blood is estimated, and the prevailing theories of secretion are reviewed. All are found inadequate.