Regulation of renal proximal and distal tubule transport: Sodium, chloride and organic anions

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55 Scopus citations

Abstract

Renal tubular transport and its regulation are reviewed for Na+ (and Cl-), and for fluid and organic anions (including urate). Filtered Na+ (and Cl-) is reabsorbed along the tubules but only in mammals and birds does most reabsorption occur in the proximal tubules. Reabsorption involves active transport of Na+ and passive reabsorption of Cl-. The active Na+ step always involves Na-K-ATPase at the basolateral membrane, but the entry step at luminal membrane varies among tubule segments and among vertebrate classes (except for Na +-2Cl--K+ cotransporter in diluting segment). Regulation can involve intrinsic, neural and endocrine factors. Proximal tubule fluid reabsorption is dependent on Na+ reabsorption in all vertebrates studied, except ophidian reptiles. Fluid secretion occurs in glomerular and aglomerular fishes, reptiles and even mammals, but its significance is not always clear. A non-specific transport system for net secretion of organic anions (OAs) exists in the proximal renal tubules of almost all vertebrates. Net transepithelial secretion involves: (1) transport into the cells at the basolateral side against an electrochemical gradient by a tertiary active transport process, in which the final step involves OA/α-ketoglutarate exchange and (2) movement out of the cells across the luminal membrane down an electrochemical gradient by unknown carrier-mediated process(es). Regulation may involve protein kinase C and mitogen-activated protein kinase. Urate is net secreted in the proximal tubules of birds and reptiles. This process is urate-specific in reptiles but in birds, it may involve both a urate-specific system and the general OA system.

Original languageEnglish (US)
Pages (from-to)453-478
Number of pages26
JournalComparative Biochemistry and Physiology - A Molecular and Integrative Physiology
Volume136
Issue number3
DOIs
StatePublished - Nov 2003

Keywords

  • Chloride
  • Epithelial transport
  • Fluid transport
  • Non-mammalian vertebrates
  • Organic anions
  • Renal tubules
  • Sodium
  • Transport regulation
  • Urate

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Molecular Biology

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