Oxalate absorption and postprandial urine supersaturation in an experimental human model of absorptive hypercalciuria

Clin Sci (Lond). 1984 Jul;67(1):131-8. doi: 10.1042/cs0670131.

Abstract

The effect of 1.25-dihydroxyvitamin D [1,25-(OH)2D] on dietary oxalate absorption and postprandial urine supersaturation with calcium oxalate was determined in 11 normal subjects. 1,25-(OH)2D increased the urinary excretion of orally administered [14C]oxalate in the 8 h period after a liquid meal containing 1.875 mmol of calcium and 0.83 mmol of oxalate (P less than 0.01), and during a 48 h period when the subjects ingested a diet containing 25 mmol of calcium and 3.3 mmol of oxalate/day (P less than 0.01); however, 1,25-(OH)2D administration had no effect on [14C]oxalate excretion when calcium was removed from the liquid meal. 1.25-(OH)2D increased 24 h urinary oxalate excretion from 28.7 +/- 2.1 mmol/mol of creatinine to 36.8 +/- 2.6 mmol/mol of creatinine (P less than 0.05) on the 10 mmol/day calcium diet and from 26.4 +/- 2.9 to 33.2 +/- 2.2 mmol/mol of creatinine (P less than 0.1) on the 25 mmol/day calcium diet. A linear correlation (r = 0.72) was found between plasma 1,25-(OH)2D levels and urinary [14C]oxalate excretion after the liquid meal. 1,25-(OH)2D administration produced postprandial supersaturation of urine with calcium oxalate and calcium oxalate crystalluria. These studies suggest that 1,25-(OH)2D increases oxalate absorption (and urinary excretion) by increasing calcium absorption, which results in less binding of calcium to oxalate in the intestine; therefore more oxalate is available for absorption. The combined effect of increased calcium and oxalate absorption results in postprandial supersaturation of urine with calcium oxalate, with resultant crystalluria.

Publication types

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

MeSH terms

  • Adult
  • Calcitriol
  • Calcium / administration & dosage
  • Calcium / metabolism*
  • Calcium Metabolism Disorders / chemically induced
  • Calcium Oxalate / urine*
  • Crystallization
  • Fasting
  • Female
  • Humans
  • Intestinal Absorption / drug effects
  • Male
  • Osmolar Concentration
  • Oxalates / metabolism*
  • Oxalic Acid

Substances

  • Oxalates
  • Calcium Oxalate
  • Oxalic Acid
  • Calcitriol
  • Calcium