AJP - Renal Physiology, Vol 249, Issue 3 400-F408, Copyright © 1985 by American Physiological Society
Sodium-pyrazinoate cotransport in rabbit renal brush border membrane vesicles
M. Manganel, F. Roch-Ramel and H. Murer
Pyrazinoate (PZA) is an organic anion actively reabsorbed and secreted in
the mammalian kidney. In experiments with rabbit renal brush border
membrane vesicles, we characterized a sodium-PZA cotransport mechanism that
could be involved in reabsorption. An inwardly directed sodium gradient
stimulated the influx of PZA. The sodium-dependent transport was
electroneutral, suggesting a 1:1 stoichiometry. The kinetic constants for
sodium-PZA cotransport were measured under initial linear flux and zero
trans conditions for both sodium and PZA. The apparent Km for sodium was
about 60 mM. At 90 mM sodium the apparent Km for PZA was about 1.1 mM;
increasing the sodium concentration augmented the apparent affinity for
PZA. Cis inhibition of sodium-dependent PZA uptake was observed by the
addition of nicotinate, lactate, probenecid, succinate,
beta-hydroxybutyrate, and salicylate. Urate had no effect. [14C]PZA uptake
was trans stimulated by PZA itself, lactate, and nicotinate. PZA shares a
transport system(s) involved in the proximal tubular reabsorption of these
two anions.
