ULTRASTRUCTURAL-LOCALIZATION OF H(+)ATPASE IN RABBIT CORTICAL COLLECTING DUCT

In contrast to results obtained in the rat kidney, studies of H(+)ATPa se localization in the rabbit kidney have failed to demonstrate basola teral plasma membrane H(+)ATPase immunoreactivity in intercalated cell s in the cortical collecting duct (CCD). Previous studies have relied on light microscopic immunofluorescence techniques, which have limited resolution. Therefore, the immunogold procedure was used to localize H(+)ATPase in rabbit collecting ducts at the ultrastructural level. Ra bbit kidneys were preserved in vivo with periodate-lysine-paraformalde hyde or glutaraldehyde solutions, and samples of cortex were embedded in Lowicryl K4M. Thin sections were labeled for H(+)ATPase by the immu nogold procedure with a rabbit polyclonal antibody against the 70-kd s ubunit of bovine brain H(+)ATPase. Three patterns of localization of H (+)ATPase were observed. The majority of intercalated cells in the CCD exhibited label over cytoplasmic vesicles only. In these cells, no la bel was associated with either the apical or basolateral plasma membra nes. In a second group of cells, label for H(+)ATPase was observed alo ng the basolateral plasma membrane and over cytoplasmic vesicles throu ghout the cell. Rarely, intercalated cells with H(+)ATPase label along the apical plasma membrane and over the apical cytoplasmic vesicles w ere observed in the CCD. In the initial collecting tubule and connecti ng segment, intercalated cells with either pronounced apical or basola teral plasma membrane label prevailed, whereas few cells exhibited lab el restricted to the cytoplasmic vesicles. In summary, in the rabbit C CD, three patterns of H(+)ATPase distribution exist in intercalated ce lls, two of which conform to published models of type A and type B int ercalated cells.