Plasma 1,25-(OH)2-vitamin D concentrations and net intestinal calcium, phosphate, and magnesium absorption in humans.
We evaluated the relationship between plasma concentrations of the renal hormone 1,25-(OH)2-vitamin D and net intestinal absorption of Ca, PO4, and Mg in vitamin D-replete patients eating similar diets, who had undetectable, normal or elevated plasma 1,25-(OH)2-D levels, Net intestinal Ca absorption was positively correlated to plasma 1,25-(OH)2-D concentrations: percentage dietary Ca absorbed = 10 + 0.17 x plasma total 1,25-(OH)2-3, pmole/liter, r = + 0.58; P less than 0.001. By contrast, there was no significant correlation between PO4 or Mg absorption and plasma 1,25-(OH)2-D concentrations. Moreover, significant quantities of PO4 and Mg were absorbed in the absence of detectable plasma 1,25-(OH)2-D. We conclude that net intestinal Ca absorption is critically dependent upon the availability of the renal hormone 1,25-(OH)2-D in vitamin D-replete humans when dietary Ca intake is normal. By contrast, other factors must play a dominant role in regulating net intestinal PO4 and Mg absorption.
D000328:Adult; D002118:Calcium / Q000378:metabolism*; D004100:Dihydroxycholecalciferols / Q000097:blood*; D005243:Feces / Q000032:analysis; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D007408:Intestinal Absorption; D007668:Kidney / Q000502:physiology; D007669:Kidney Calculi / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy; D010710:Phosphates / Q000378:metabolism*; D006435:Renal Dialysis
D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D010710:Phosphates; D008274:Magnesium; D002118:Calcium