Intestinal absorption of calcium: role of dietary phosphate and vitamin D.
The intestinal absorption of calcium (Ca) has been shown to depend on vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and dietary phosphorus (P) concentration. This study was designed to evaluate the role of dietary P independent of vitamin D3 or 1,25(OH)2D3. Vitamin D-deficient rats were studied during dietary P restriction and were compared with control groups raised on a normal-phosphorus diet (NP). Balance studies were sued. Net intestinal Ca absorption was significantly lower with dietary P restriction compared with the NP group. This malabsorption of Ca was corrected by the administration of either D3 for 1,25(OH)2D3, despite hypophosphatemia. Everted gut sacs showed a marked reduction in the uptake of 45Ca in the duodenum, jejunum, and ileum during dietary P restriction. We concluded that dietary P concentration plays a major role in intestinal Ca absorption in the vitamin D-deficient rats. These findings suggest an effect of the low-phosphate diet on the vitamin D-dependent, Ca-transport mechanism.
D000818:Animals; D002117:Calcitriol; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D002762:Cholecalciferol / Q000494:pharmacology*; D004100:Dihydroxycholecalciferols / Q000494:pharmacology*; D006887:Hydroxycholecalciferols / Q000494:pharmacology*; D007408:Intestinal Absorption / Q000187:drug effects*; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008297:Male; D010710:Phosphates / Q000494:pharmacology*; D051381:Rats
D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D010710:Phosphates; D002762:Cholecalciferol; D002117:Calcitriol; D002118:Calcium