title: Effect of vitamin D3 on duodenal calcium absorption in vivo during early development.
abstract: The effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and vitamin D deficiency on duodenal calcium absorption in suckling and weaned rats was determined by an in situ loop technique. In vitamin D-replete (+D) rats, the linear, or nonsaturable, component of calcium absorption was very efficient in 14-day-old pups and decreased with age until 35 days. The saturable component, which was undetectable in 14-day-old pups, became detectable by 18 days of age and increased until 26 days of age. Calcium absorption was not reduced in vitamin D-deficient (-D) 14-day-old pups as compared with +D pups. A high dose of 1,25(OH)2D3 increased the plasma calcium level of +D suckling rats but had no effect on calcium absorption even with milk present in the loop. Weaned -D rats had a reduced saturable component of absorption (P less than 0.01) compared with +D rats. A high dose of 1,25(OH)2D3 significantly increased calcium absorption and plasma calcium levels of -D rats. Our results indicate that during suckling calcium absorption occurs by a process that is insensitive to vitamin D. After weaning both saturable and nonsaturable processes appear to contribute to calcium absorption, and the saturable component can be influenced by vitamin D status or a high dose of 1,25(OH)2D3.
mesh_terms: D000375:Aging; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D004386:Duodenum / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D005260:Female; D007408:Intestinal Absorption / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D051381:Rats; D014808:Vitamin D Deficiency / Q000378:metabolism*
chemical_list: D002117:Calcitriol; D002118:Calcium