APStracts 2:0125F, 1995.

Indirect coupling of urate and p-aminohippurate transport to sodium in human brush-border membrane vesicles. Roch-Ramel, Francoise, Barbara Guisan, and Laurent Schild. Institut de Pharmacologie et Toxicologie de l'Universit[acute]e, CH 1005 Lausanne, Switzerland

APStracts 2:0125F, 1995.

ob]14C]-urate and [14C]-p-aminohippurate (PAH) uptake by human brush -border membrane vesicles (BBMV) were measured in the presence of an inwardly oriented sodium gradient. No direct sodium cotransport was observed. Indirect [14C]-urate coupling to sodium transport was demonstrated by cis-stimulation of [14C]-urate with nicotinate or pyrazinoate (PZA) in the extravesicular medium, but not by adding lactate, [alpha] -ketoglutarate, or [beta] -hydroxybutyrate. Indirect sodium coupling of [14C]-PAH uptake was observed only when [alpha] -ketoglutarate was added to the extravesicular medium, a mechanism similar to that of basolateral membranes. The ability for PZA (and nicotinate) to cis-stimulate urate uptake was correlated with a high apparent affinity for the urate/anion exchanger. In urate loaded vesicles, for identical medium concentrations, [14C]-PZA uptake via the urate-anion exchanger was ten time higher than [14C]-lactate uptake. Such high PZA affinity for the urate exchanger, working in parallel with PZA sodium-cotransport can account for the stimulation of urate reabsorption by PZA in vivo.

Received 8 February 1995; accepted in final form 23 June 1995.
APS Manuscript Number F46-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.