AJP - Renal Physiology, Vol 251, Issue 2 232-F237, Copyright © 1986 by American Physiological Society
Amiloride-inhibited Na+-H+ exchange in human kidney medulla microsomes
E. F. LaBelle
Membrane vesicles from the medulla of the human kidney are capable of
amiloride-inhibited sodium-proton exchange. Sodium uptake into the vesicles
is stimulated by low intravesicular pH (6.0) and inhibited by both low
extravesicular pH (6.0) and amiloride (2 mM). Sodium uptake is a linear
function of the vesicular protein concentration and can be reversed by
raising the osmotic strength of the solution to shrink the vesicles or by
adding the ionophore nigericin. Acridine orange was accumulated by the
vesicles in response to a pH gradient (pH 6.0, inside, 8.0 outside), and
the accumulation of acridine orange could be reduced by increased
extravesicular sodium. Thus sodium could stimulate proton movement just as
protons could stimulate sodium movement across the vesicular membrane.
