Citrate and succinate transport in proximal tubule cells.

Abstract

Urinary citrate, which inhibits calcium nephrolithiasis, is determined by proximal reabsorption via an apical dicarboxylate transporter. Citrate is predominantly trivalent at physiological pH, but citrate(-2) is transported at the apical membrane. We now demonstrate that low-Ca solutions induce transport of citrate(-2) and succinate in opossum kidney cells. With 1.2 mM extracellular Ca, citrate uptake was pH insensitive and not competed by succinate(-2). In contrast, with low extracellular Ca, citrate uptake increased twofold, was inhibited by succinate (and other dicarboxylates), was stimulated by lowering extracellular pH (consistent with citrate(-2) transport), and increased further by lowering extracellular Mg. The effect of Ca was incrementally concentration dependent, between 0 and 1.2 mM. The effect of Ca was not simply complexation with citrate because succinate (which is complexed significantly less) was affected by Ca similarly. Incubation of cells for 48 h in a low-pH media increased citrate transport (studied at control pH) more than twofold, suggesting induction of transporters.

• Authors: K S Hering-Smith, C T Gambala, L L Hamm
• Journal: American journal of physiology. Renal physiology (Am J Physiol Renal Physiol) Vol. 278 Issue 3 Pg. F492-8 (Mar 2000) ISSN: 1931-857X [Print] United States
• PMID: 10710554 (Publication Type: Journal Article)

Chemical References

• Carrier Proteins
• Dicarboxylic Acid Transporters
• Solutions
• Citric Acid
• Sodium
• Succinic Acid
• Magnesium
• Calcium

Topics

• Acidosis (metabolism)
• Animals
• Biological Transport (drug effects)
• Calcium (metabolism, pharmacology)
• Carrier Proteins (metabolism)
• Cells, Cultured
• Citric Acid (antagonists & inhibitors, pharmacokinetics)
• Dicarboxylic Acid Transporters
• Extracellular Space (metabolism)
• Hydrogen-Ion Concentration
• Kidney Tubules, Proximal (cytology, metabolism)
• Magnesium (metabolism)
• Opossums
• Sodium (physiology)
• Solutions
• Substrate Specificity
• Succinic Acid (pharmacokinetics, pharmacology)