title: Up-regulation of the intestinal 1,25-dihydroxyvitamin D receptor during hypervitaminosis D: a comparison between vitamin D2 and vitamin D3.
abstract: Concentrations of intestinal 1,25-dihydroxyvitamin D receptor were measured in rats receiving pharmacological amounts (25,000 IU/rat daily for 6 days) of either vitamin D2 or vitamin D3. The data showed that both hypervitaminosis D2 and hypervitaminosis D3 resulted in significant up-regulation of intestinal 1,25-dihydroxyvitamin D receptor (fmol/mg protein) relative to controls (409 +/- 24, vitamin D2-treated; 525 +/- 41, vitamin D3-treated; and 249 +/- 19, control). The 1,25-dihydroxyvitamin D receptor enhancement also was accompanied by elevated plasma 25-hydroxyvitamin D and hypercalcemia. These data suggest that increased target-tissue 1,25-dihydroxyvitamin D receptor may play a role in enhancing target-tissue responsiveness and, thus, have a significant role in mediating the toxic effects of hypervitaminosis D.
authors.affiliation: National Animal Disease Center, Agriculture Research Service, USDA, Ames, IA 50010.
authors.forename: M J
authors.initials: MJ
authors.lastname: Beckman
authors.forename: R L
authors.initials: RL
authors.lastname: Horst
authors.forename: T A
authors.initials: TA
authors.lastname: Reinhardt
authors.forename: D C
authors.initials: DC
authors.lastname: Beitz
mesh_terms: D000818:Animals; D001835:Body Weight; D002117:Calcitriol / Q000097:blood / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D004872:Ergocalciferols / Q000097:blood / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D004872:Ergocalciferols; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D002117:Calcitriol; D002118:Calcium