engleski

Ecto-ATPase activity and labeling with the anti-ecto- ATPase antibody in renal brush border do not coincide

The ecto-ATPase from rat liver has reportedly been cloned and respective antibodies generated. However, the identity of the cloned protein has recently been challenged because the "rat liver ecto-ATPase cDNA" encoded a protein which exhibited no ATPase activity (A. F. Knowles, Biochem, Biophys. Res. Commun. 207:529-535, 1995). Using an antibody against the putative liver ecto-ATPase/cell-CAM 105 (A669), we labeled the respective 105 kDa protein band in Western blots (WB) of brush- border membrane vesicles isolated from superficial (SC) and deep cortex (DC), and outer stripe of the outer medulla (OS), and compared it with the ecto-ATPase acitivity measured by the Pi-liberation assay in the same vesicles. The density pattern of the 105 kDa protein band in WB completely correlated with the endothelial cell plasma membrane marker, thrombomodulin (SC<DC<OS), whereas the ecto-ATPase activity showed an exactly oposite pattern and correlated well with distribution of the bafilomycin-sensitive H+-ATPase (SC>DC>OS). The data indicate that the antibody A669 may not be specific for the renal brush-border ecto-ATPase.

ecto-ATPase ; cell adhesion molecule C-CAM 105 ; brush-border membrane ; kidney

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