Effects of a high-sodium/low-potassium Diet on Renal Calcium, Magnesium, and Phosphate Handling

Am J Physiol Renal Physiol. 2018 Jul 1;315(1):F110-F122. doi: 10.1152/ajprenal.00379.2017. Epub 2018 Jan 10.

Abstract

The distal convoluted tubule (DCT) of the kidney plays an important role in blood pressure regulation by modulating Na+ reabsorption via the Na+-Cl- cotransporter (NCC). A diet containing high salt (NaCl) and low K+ activates NCC, thereby causing Na+ retention and a rise in blood pressure. Since high blood pressure, hypertension, is associated with changes in serum calcium (Ca2+) and magnesium (Mg2+) levels, we hypothesized that dietary Na+ and K+ intake affects Ca2+ and Mg2+ transport in the DCT. Therefore, the present study aimed to investigate the effect of a high-Na+/low-K+ diet on renal Ca2+ and Mg2+ handling. Mice were divided in four groups and fed a normal-Na+/normal-K+, normal-Na+/low-K+, high-Na+/normal-K+, or high-Na+/low-K+ diet for 4 days. Serum and urine were collected for electrolyte and hormone analysis. Gene and protein expression of electrolyte transporters were assessed in kidney and intestine by qPCR and immunoblotting. Whereas Mg2+ homeostasis was not affected, the mice had elevated urinary Ca2+ and phosphate (Pi) excretion upon high Na+ intake, as well as significantly lower serum Ca2+ levels in the high-Na+/low-K+ group. Alterations in the gene and protein expression of players involved in Ca2+ and Pi transport indicate that reabsorption in the proximal tubular and TAL is affected, while inducing a compensatory response in the DCT. These effects may contribute to the negative health impact of a high-salt diet, including kidney stone formation, chronic kidney disease, and loss of bone mineral density.

Keywords: calcium; kidney; phosphate; potassium; salt.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Feed
  • Animals
  • Calcium / blood
  • Calcium / metabolism*
  • Calcium / urine
  • Gene Expression Regulation
  • Homeostasis
  • Kidney Tubules, Distal / metabolism*
  • Magnesium / blood
  • Magnesium / metabolism*
  • Magnesium / urine
  • Male
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Mice, Inbred C57BL
  • Phosphates / blood
  • Phosphates / metabolism*
  • Phosphates / urine
  • Potassium, Dietary / administration & dosage*
  • Potassium, Dietary / metabolism
  • Renal Reabsorption*
  • Sodium Chloride, Dietary / administration & dosage*
  • Sodium Chloride, Dietary / metabolism
  • Time Factors

Substances

  • Membrane Transport Proteins
  • Phosphates
  • Potassium, Dietary
  • Sodium Chloride, Dietary
  • Magnesium
  • Calcium