Dietary phosphate and parathyroid hormone alter the expression of the calcium-sensing receptor (CaR) and the Na+-dependent Pi transporter (NaPi-2) in the rat proximal tubule

Pflugers Arch. 2000 Dec;441(2-3):379-87. doi: 10.1007/s004240000436.


Dietary phosphate (Pi) intake and parathyroid hormone (PTH) are essential regulators of proximal tubular (PT) Pi reabsorption; both factors are associated with adaptive changes in PT apical brush border membrane (BBM) Na/Pi-cotransport activity and specific transporter protein (NaPi-2) content. Urinary Pi excretion is also inversely correlated with luminal Ca2+ concentration ([Ca2+]) both in a PTH-dependent and -independent fashion. A cell-surface, Ca2+(/polyvalent cation)-sensing receptor (CaR) has been localized to the PT BBM with unknown function. To investigate whether PTH and/or dietary Pi intake could affect the distribution or the expression of the CaR, we evaluated their effects on rat kidney CaR and the NaPi-2 expression by Western blot analysis and immunofluorescence microscopy. A chronic high-Pi (1.2%) versus low-Pi (0.1%) diet and acute PTH (1-34) infusion significantly reduced the PT BBM expression of both NaPi-2 and CaR proteins. CaR-specific immunoreactivity in nephron segments other than the PT was not affected by PTH or Pi intake. These results suggest that reduced renal PT CaR expression by a high-Pi diet and by increased circulating PTH levels could contribute to the local control of PT handling of Ca2+ and Pi.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blotting, Western
  • Carrier Proteins / analysis*
  • Diet
  • Fluorescent Antibody Technique
  • Kidney Tubules, Proximal / chemistry*
  • Kidney Tubules, Proximal / drug effects
  • Kidney Tubules, Proximal / metabolism
  • Male
  • Microscopy, Fluorescence
  • Parathyroid Hormone / blood
  • Parathyroid Hormone / pharmacology*
  • Phosphate-Binding Proteins
  • Phosphates / administration & dosage
  • Phosphates / metabolism
  • Phosphates / pharmacology*
  • Phosphates / urine
  • Rats
  • Rats, Wistar
  • Receptors, Calcium-Sensing
  • Receptors, Cell Surface / analysis*
  • Sodium / pharmacology*


  • Carrier Proteins
  • Parathyroid Hormone
  • Phosphate-Binding Proteins
  • Phosphates
  • Receptors, Calcium-Sensing
  • Receptors, Cell Surface
  • extracellular calcium cation-sensing receptor, rat
  • Sodium