Detection and localization of H+-K+-ATPase isoforms in human kidney

An H+-K+-ATPase contributes to hydrogen secretion and potassium reabsorptio n by the rat and rabbit collecting ducts. Transport of these ions appears t o be accomplished by one or both of two isoforms of the H+-K+-ATPase, HK al pha (1) and HK alpha (2), because both isoforms are found in the collecting ducts and transport of hydrogen and potassium is attenuated by exposure to inhibitors of these transport proteins. To evaluate whether an H+-K+-ATPas e is present in the human kidney, immunohistochemical studies were performe d using normal human renal tissue probed with antibodies directed against e pitopes of three of the known isoforms of the H+-K+-ATPase, HK alpha (1), H K alpha (2), and HK alpha (4), and the V-type H+-ATPase. Cortical and medul lary tissue probed with antibodies against HK alpha (1) showed cytoplasmic staining of intercalated cells that was less intense than that observed in the parietal cells of normal rat stomach stained with the same antibody. Al so, weak immunoreactivity was detected in principal cells of the human coll ecting ducts. Cortical and medullary tissue probed with antibodies directed against HK alpha (4) revealed weak, diffuse staining of intercalated cells of the collecting ducts and occasional light staining of principal cells. Cortical and medullary tissue probed with antibodies directed against the H +-ATPase revealed staining of intercalated cells of the collecting ducts an d some cells of the proximal convoluted tubules. By contrast, no discernibl e staining was noted with the use of the antibody against HK alpha (2), The se data indicate that HK alpha (1). and HK alpha (4) are present in the col lecting ducts of the human kidney. In this location, these isoforms might c ontribute to hydrogen and potassium transport by the kidney.