Facilitated diffusion of urate in avian brush-border membrane vesicles

• Published in: American Journal of Physiology: Cell Physiology 2002-10, Vol.283 (4), p.C1155-C1162
• Main Author: Grassl, Steven M
• Format: Article
• Language: English
• Subjects: Animals; Biological Transport - drug effects; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone - pharmacology; Carrier Proteins - metabolism; Cell Membrane - chemistry; Cell Membrane - metabolism; Chlorides - metabolism; Diffusion; Hydrogen-Ion Concentration; Ionophores - pharmacology; Ketoglutaric Acids - metabolism; Ketoglutaric Acids - pharmacokinetics; Kidney Tubules, Proximal - chemistry; Kidney Tubules, Proximal - metabolism; Membrane Potentials - physiology; Microvilli - chemistry; Microvilli - metabolism; Organic Anion Transporters; p-Aminohippuric Acid - pharmacokinetics; Subcellular Fractions - chemistry; Subcellular Fractions - metabolism; Turkeys; Uric Acid - metabolism; Uric Acid - pharmacokinetics
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00380.2001

Department of Pharmacology, State University of New York, Upstate Medical University, Syracuse, New York 13210 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 -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. organic anion secretion; renal proximal tubule; urate transporter