title: Homologous up-regulation of the 1,25 (OH)2 vitamin D3 receptor in rats.
abstract: This study investigates the ability of vitamin D-metabolites to regulate 1,25(OH)2D3 receptors in vivo. Rats made vitamin D-deficient were treated with 1,25(OH)2D3 or vehicle for 1-5 days. In treated animals, receptors for 1,25(OH)2D3 in kidney increased dramatically compared with control levels. An increase in specific binding to 220% of control was seen after 2 doses of hormone, which reached to 336% after 5 days of treatment. Intestinal receptors increased to only 130% of control levels after 5 days of treatment. In vitamin D-replete animals, the difference between control and treated groups was slightly greater when endogenously occupied sites were measured by exchange (TPCK). However, significant changes were observed only after 4 days of hormone treatment. The data indicate that homologous up-regulation of the 1,25(OH)2D3 receptor occurs in vivo. The difference in response in kidney and in intestine suggests differential importance of up-regulation in various organs.
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects* / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000378:metabolism
chemical_list: D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D002117:Calcitriol