Relation of ATPases in rat renal brush-border membranes to ATP-driven H super(+) secretion

In the presence of inhibitors of mitochondrial H super(+) ATPase (Na super(+) + K super(+))- and Ca super(2+)-ATPases, and alkaline phosphatase, sealed brush-border membrane vesicles hydrolyse externally added ATP demonstrating the existence of ATPases at the outside of the membrane ("ecto-ATPases"). These ATPases accept several nucleotides, are stimulated by Ca super(2+) and Mg super(2+), and are inhibited by N,N'-dicyclohexylcarbodiimide (DCCD), but not by N-ethylmaleimide (NEM). These data prove the coexistence of Na super(+)-coupled substrate transporters, Na super(+)/H super(+) exchanger, and an ATP-driven H super(+) pump in brush-border membrane vesicles. Similar location and inhibitor sensitivity reveal the identity of ATP-driven H super(+) pumps with (a part of) the DCCD- and NEM-sensitive ATPases at the cytosolic side of the brush-border membrane.