Immunohistochemical localization of H-K-ATPase alpha(2c)-subunit in rabbitkidney

The rabbit kidney possesses mRNA for the H-K-ATPase alpha (1)-subunit (HK a lpha (1)) and two splice variants of the H-K-ATPase alpha (2)-subunit (HK a lpha (2)). The purpose of this study was to determine the specific distribu tion of one of these, the H-K-ATPase alpha (2c)-subunit isoform (HK alpha ( 2c)), in rabbit kidney by immunohistochemistry. Chicken polyclonal antibodi es against a peptide based on the NH2 terminus of HK alpha (2c) were used t o detect HK alpha (2c) immunoreactivity in tissue sections. Immunohistochem ical localization of HK alpha (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 stri pe. An additional population of cells exhibited a thin apical band of immun olabel. Immunohistochemical colocalization of HK alpha (2c) with carbonic a nhydrase II, the Cl-/HCO3- exchanger AE1, and HK alpha (1) indicated that b oth type A and type B intercalated cells possessed intense apical HK alpha (2c) immunoreactivity, whereas principal cells and connecting segment cells had only a thin apical band of HK alpha (2c). Labeled cells were evident t hrough the middle third of the inner medullary collecting duct in the major ity of animals. Immunolabel was also present in papillary surface epithelia l cells, cells in the cortical thick ascending limb of Henle's loop (cTAL), and the macula densa. Thus in the rabbit kidney, apical HK alpha (2c) is p resent and may contribute to acid secretion or potassium uptake throughout the connecting segment and collecting duct in both type A and type B interc alated cells, principal cells, and connecting segment cells, as well as in cells in papillary surface epithelium, cTAL, and macula densa.