Abstract
Potassium-dependent phosphatase activity can be demonstrated in unfixed frozen sections of mouse stomach using either adenosine triphosphate (ATP) or p-nitrophenyl phosphate (NPP) as substrate. In both cases the potassium-dependent reaction is confined to oxyntic cells, but with ATP, a strong, potassium-independent reaction occurs in the connective tissue of the lamina propria and elsewhere. In the NPP system potassium-independent reaction is very slight, and the oxyntic cell reaction shows responses to inhibitors that differentiate it from Na+, K+-ATPase and that are consistent with its identification with the dephosphorylation step of the proton pump enzyme H+, K+-ATPase, recognized as the active transport component in gastric acid secretion.