Electron-microscopic immunogold localization of a collecting-duct antigen (PCD2) in intercalated and principal cells of rabbit kidney.

A monoclonal antibody against an antigen (PCD2) derived from the rabbit renal papilla recognized principal and intercalated cells of the collecting duct system in the adult rabbit kidney. Intercalated cells were heterogeneous in the connecting tubule and the cortical collecting duct, where immunoreactive and unreactive cells were shown to coexist. In the outer medullary collecting duct, all intercalated cells exhibited PCD2-immunoreactivity. Connecting tubule cells proper were not recognized by the antibody, whereas all principal cells of the collecting duct revealed specific immunoreactivity. The immunocytochemical heterogeneity of the intercalated cells is discussed in terms of a functional heterogeneity. Cytologically, the immunogold labeling of principal and intercalated cells was shown to occur along the plasmalemma, in the intracellular membrane structures and along the Golgi transport route. This pattern suggests that the antigenic determinant, which is ubiquitous in both principal and reactive intercalated cells, belongs to a membrane protein.