IMMUNOCYTOCHEMICAL LOCALIZATION OF VACUOLAR H-ATPASE IN THE OPOSSUM (MONODELPHIS-DOMESTICA) KIDNEY - COMPARISON WITH THE RAT

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 differe nt nephron segments of the gray short-tailed (Monodelphis domestica) o possum kidney has been immunocytochemically localized. There was moder ate staining of the brush border and subvillar invaginations in the pr oximal convoluted tubules (PCT) of the opossum kidney only with the ra bbit antiserum and not with the monoclonal antibody. This was in contr ast to the rat kidney, where both antibodies showed significant staini ng of the brush border and subvillar invaginations. There was very min imal staining in the apical region of the thick ascending limb cells o f 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 int ercalated cells in the outer and inner medullary collecting ducts were less polarized in the opossum kidney. These findings suggest that dif ferent isoforms of H-ATPase exist in the brush border of the PCT versu s the intercalated cells of the collecting duct in the opossum and bet ween the PCT of opossum and rat kidneys.