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Updated: Aug 3, 2026

Expression, Solubilization, and Purification of Eukaryotic Borate Transporters
Published on: March 7, 2019
Facilitated diffusion of urate in avian brush-border membrane vesicles
1Department of Pharmacology, State University of New York, Upstate Medical University, 766 Irving Avenue, Syracuse, NY 13210, USA. grassls@upstate.edu
Abstract:
Membrane transport pathways mediating transcellular secretion of urate across the proximal tubule were investigated in brush-border membrane vesicles (BBMV) isolated from avian kidney. An inside-positive K diffusion potential induced a conductive uptake of urate to levels exceeding equilibrium. Protonophore-induced dissipation of membrane potential significantly reduced voltage-driven urate uptake. Conductive uptake of urate was inhibitor sensitive, substrate specific, and a saturable function of urate concentration. Urate uptake was trans-stimulated by urate and cis-inhibited by p-aminohippurate (PAH). Conductive uptake of PAH was cis-inhibited by urate. Urate uptake was unaffected by an outward alpha-ketoglutarate gradient. In the absence of a membrane potential, urate uptake was similar in the presence and absence of an imposed inside-alkaline pH gradient or an outward Cl gradient. These observations suggest a uniporter-mediated facilitated diffusion of urate as a pathway for passive efflux across the brush border membrane of urate-secreting proximal tubule cells.
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