AJP - Renal Physiology, Vol 251, Issue 2 297-F302, Copyright © 1986 by American Physiological Society
ATP-dependent proton transport in human renal medulla
F. D. Diaz-Diaz, E. F. LaBelle, D. C. Eaton and T. D. DuBose Jr
An electrogenic proton-translocating ATPase (H+-ATPase) has been described
in turtle urinary bladder and bovine and rat renal medulla. In the present
study, a membrane fraction with ATP-dependent H+ transport activity was
isolated from human renal medulla. Intravesicular acidification was
assessed by acridine orange absorbance changes. Proton transport was
abolished by N-ethylmaleimide but not oligomycin or vanadate,
differentiating this H+-ATPase from mitochondrial F0-F1 H+-ATPase and
gastric H+-K+-ATPase. In addition, vesicular proton uptake was demonstrated
to be independent of sodium and potassium cotransport. Proton translocation
rate increased when transmembrane potential was clamped with valinomycin
supporting an electrogenic mechanism. Hydrogen ion transport was dependent
on the presence of chloride or bromide, since substitution by fluoride or
nitrate markedly decreased intravesicular acidification. The transport
characteristics of this proton-translocating ATPase are similar to those
described for turtle urinary bladder and bovine and rat renal medulla,
which have been assumed to play a role in urinary acidification by the
medullary collecting duct.
