Expression of a protein in rat kidney and distal colon that is related to the gastric H,K-ATPase

Recent studies indicate that a gastric-like H,K-ATPase activity could account for electroneutral H-K exchange in both kidney and colon. To determine the molecular mechanism responsible for this activity, we used antibodies (HK9 and HKB) directed against two distinct epitopes of the gastric H,K-ATPase in western blot analysis of kidney and distal colon. A protein of molecular weight similar to that of the gastric H,K-ATPase was identified by one antiserum (HK9) and not by the other (HKB). The protein identified by HK9 was found to be expressed in greater abundance in the inner medulla than in cortex and outer medulla. This result suggests that, a protein similar, but not identical, to gastric H,K-ATPase may participate in proton secretion and potassium absorption in the inner medulla. We conclude that a protein that is part of a molecular family of gastric H,K-ATPase is present in kidney and distal colon.