title: 6-Fluoro-vitamin D3: a new antagonist of the biological actions of vitamin D3 and its metabolites which interacts with the intestinal receptor for 1 alpha,25(OH)2-vitamin D3.
abstract: The biological activity and the binding affinity for the 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] intestinal receptor of a new fluorine-containing vitamin D compound, namely 6-fluoro-vitamin D3 (6-F-D3), is reported. A significant interaction of 6-F-D3 with the 1,25(OH)2D3 receptor was found, with a relative competitive index (RCI) of 0.26 +/- 0.04, which is intermediate between 25-hydroxyvitamin D3 (0.14 +/- 0.01) and 1 alpha-hydroxyvitamin D3 (0.46 +/- 0.08), where the RCI of 1,25(OH)2D3 is defined to be 100. In contrast, vitamin D3 was unable to interact with the 1,25(OH)2D3 receptor. Also, the biological activity of 6-F-D3 was assessed in vivo in the vitamin D-deficient chick. 6-F-D3 at doses up to 130 nmol displayed no biological action on either intestinal calcium absorption (ICA) or bone calcium mobilization (BCM) over the time interval of 14-48 h after dosing. However, when 130 nmol 6-F-D3 was given 2 h before and 6 h after vitamin D3 (1.62 nmol), a significant inhibition of vitamin D-mediated ICA was noted. Also, a dose of 130 nmol 6-F-D3 given 2 h before and 6 h after 1,25(OH)2D3 (0.26 nmol) significantly inhibited ICA, as measured at 12 h. 6-F-D3 is the first vitamin D analog found which has an ability to both bind to the 1,25(OH)2D3 receptor and to antagonize the production of biological responses by 1,25(OH)2D3.
mesh_terms: D000818:Animals; D001681:Biological Assay; D002117:Calcitriol / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002645:Chickens; D002762:Cholecalciferol / Q000037:antagonists & inhibitors* / Q000494:pharmacology* / Q000633:toxicity / Q000031:analogs & derivatives; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; 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; D002762:Cholecalciferol; C042088:6-fluorovitamin D3; D002117:Calcitriol; D002118:Calcium