Immunocytochemical localization of vacuolar H-ATPase in the opossum (Monodelphis domestica) kidney

With two different antibodies (a monoclonal antibody to the C terminus of the 31-kd subunit of H-ATPase and a polyclonal rabbit antiserum to whole bovine H-ATPase) the vacuolar-type H-ATPase pump in the different nephron segments of the gray short-tailed (Monodelphis domestica) opossum kidney has been immunocytochemically localized. There was moderate staining of the brush border and subvillar invaginations in the proximal convoluted tubules (PCT) of the opossum kidney only with the rabbit antiserum and not with the monoclonal antibody. This was in contrast to the rat kidney, where both antibodies showed significant staining of the brush border and subvillar invaginations. There was very minimal staining in the apical region of the thick ascending limb cells of the opossum as compared with a mild degree present in the rat kidney. The pattern and intensity of staining were similar in the remaining distal nephron segments with the only difference being that type A intercalated cells in the outer and inner medullary collecting ducts were less polarized in the opossum kidney. These findings suggest that different isoforms of H-ATPase exist in the brush border of the PCT versus the intercalated cells of the collecting duct in the opossum and between the PCT of opossum and rat kidneys.