Utilization of High-Energy Phosphate Compounds by Stomach

The frog gastric mucosa in vitro secretes HC1 and maintains its electrical activity for many hours. Both processes depend on the active transport of C1 ion and are inhibited under appropriate conditions by SCN ion. I t has been suggested that a membranebound ATPase from gastric mucosa is involved, since this ATPase is also inhibited by SCN (8). I t furthermore is stimulated by physiological concentrations of HCO3, an ion which potentiates acid production (6) and reverses inhibition of electrical activity by SCN (9). Sachs, Mitch, and Hirschowitz confirmed the sensitivity of the gastric ATPase to SCN; they pointed out, however, that ATPase from rat liver mitochondria and brush border of hamster intestine were also inhibited by SCN (15). Furthermore, HCOa stimulates mitochondrial ATPase to about the same extent as gastric ATPase (14). The effects of SCN and HCO3 are thus not specific for the gastric ATPase. The significance of this lack of specificity is not clear, however. I t may indicate that the gastric ATPase is of mitochondrial origin, or instead that SCN and H C O a act on a variety of enzymes. Of pr imary importance in evaluating an ATPase theory would be proof as to whether ATP is actually an intermediate in active transport by stomach. Forte, Adams, and Davies have answered this question in the affirmative, on the basis of the stoichiometry between acid produced and ATP consumed during prolonged anoxia (3). Their experiments are open to criticism, however, since they did not measure electrical activity or follow changes in tissue phosphocreatine. In the first part of the present studies, the effect of anoxia has been reexamined.