The presence of H⁺,K⁺-ATPase in the crypt of rabbit distal colon demonstrated with monoclonal antibodies against gastric H⁺,K⁺-ATPase

Indirect evidence indicates the presence of an active H⁺ K⁺ antiporter for the secretion of acid in the distal colon. It was examined whether the H⁺ K⁺ antiporter in the rabbit distal colon was hydrogen-potassium-stimulated adenosine triphosphatase (H⁺,K⁺-ATPase), which acts as a proton pump in the gastric mucosa. For this purpose, four monoclonal antibodies against hog gastric H⁺,K⁺-ATPase were raised. Three monoclonal antibodies dose-dependently inhibited the ouabain-insensitive gastric ATPase activity. Antibody HK4001 completely inhibited the ATPase activity. In indirect immunofluorescence studies, all four monoclonal antibodies stained H⁺,K⁺-ATPase in gastric mucosae of various animal species. Two monoclonal antibodies including antibody HK4001 cross-reacted with H⁺,K⁺-ATPase located in crypts of the transverse and descending colon and rectum of rabbits. Because the other two antibodies did not cross-react with the H⁺,K⁺-ATPase in the colon, this colonic enzyme is similar but not identical to gastric H⁺,K⁺-ATPase. On the other hand, HK4001 and SCH 28080 did not inhibit ouabain-sensitive K⁺-dependent ATPase activity in the guinea pig distal colon, and the antibodies did not stain the enzyme in the tissue. Therefore, ouabain-sensitive H⁺ K⁺ antiporter in the guinea pig is not similar to ouabain-insensitive rabbit colonic H⁺,K⁺-ATPase.