Transport of Urate and Other Organic Anions by Anion Exchange in Human Renal Brush-Border Membrane Vesicles
| Autor: | J. Diezi, Philippe Jaeger, Barbara Guisan, Françoise Roch-Ramel |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | Cellular Physiology and Biochemistry. 6:60-71 |
| ISSN: | 1421-9778 1015-8987 |
| Popis: | Earlier studies demonstrated that an apical anion exchanger which accepts urate, chloride, aliphatic monocarboxylates, and the aromatic anions, pyrazinoate (PZA) and nicotinate, plays a major role in urate reabsorption in human proximal tubules. In substrate competition studies for transport, we investigated the effect of PZA on 50 µM [14C]-urate uptake in exchange of lactate, human brush-border membrane vesicles (BBMV) being loaded with 5 mM lactate. 1 mM PZA cis-inhibited, whereas 0.1 mM PZA cis-stimulated [14C]-urate uptake in exchange for lactate. Such paradoxical effects suggest the cooperation of two anion exchangers, PZA having more affinity for a ‘lactate/anion exchanger’ than for a ‘urate/ anion exchanger’. Apparent Km of [14C]-PZA uptake were measured in lactate- or urate-loaded BBMV, and were 0.33 ± 0.06 and 0.98 ± 0.44 mM, respectively. Unlike [14C]-PZA, [14C]-orotate and [14C]-nicotinate uptakes were stimulated only to a minor extent in BBMV loaded with lactate. In contrast, cis -inhibition studies in urate-loaded BBMV demonstrated that nicotinate and orotate had similar affinity as PZA for the ‘urate/anion exchanger’. Oxalate was shown to have affinity for the ‘lactate/anion exchanger’, but not for the ‘urate/anion exchanger’. |
| Databáze: | OpenAIRE |
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