Immunohistochemical localization of H-K-ATPase alpha(2c)-subunit in rabbit kidney.

The rabbit kidney possesses mRNA for the H-K-ATPase alpha(1)-subunit (HKalpha(1)) and two splice variants of the H-K-ATPase alpha(2)-subunit (HKalpha(2)). The purpose of this study was to determine the specific distribution of one of these, the H-K-ATPase alpha(2c)-subunit isoform (HKalpha(2c)), in rabbit kidney by immunohistochemistry. Chicken polyclonal antibodies against a peptide based on the NH(2) terminus of HKalpha(2c) were used to detect HKalpha(2c) immunoreactivity in tissue sections. Immunohistochemical localization of HKalpha(2c) revealed intense apical immunoreactivity in a subpopulation of cells in the connecting segment, cortical collecting duct, and outer medullary collecting duct in both the outer and inner stripe. An additional population of cells exhibited a thin apical band of immunolabel. Immunohistochemical colocalization of HKalpha(2c) with carbonic anhydrase II, the Cl(-)/HCO exchanger AE1, and HKalpha(1) indicated that both type A and type B intercalated cells possessed intense apical HKalpha(2c) immunoreactivity, whereas principal cells and connecting segment cells had only a thin apical band of HKalpha(2c). Labeled cells were evident through the middle third of the inner medullary collecting duct in the majority of animals. Immunolabel was also present in papillary surface epithelial cells, cells in the cortical thick ascending limb of Henle's loop (cTAL), and the macula densa. Thus in the rabbit kidney, apical HKalpha(2c) is present and may contribute to acid secretion or potassium uptake throughout the connecting segment and collecting duct in both type A and type B intercalated cells, principal cells, and connecting segment cells, as well as in cells in papillary surface epithelium, cTAL, and macula densa.