title: The biological assessment of vitamin D3 metabolites produced by rumen bacteria.
abstract: Biological assays were performed to evaluate 10-oxo-19-nor-vitamin D3 (10-oxo-D3) and 5(E) 25-hydroxy-10-oxo-19-nor-vitamin D3 (25-OH-10-oxo-D3) two bacterial products of vitamin D3 (D3) and 25-hydroxyvitamin D3 (25-OHD3) metabolism, respectively. The 5(Z) and 5(E) isomers of 10-oxo-D3 were, respectively, 40- and 80-fold less active than D3 in stimulating Ca+2 absorption from the gut. 25-Hydroxy-10-oxo-D3 did not stimulate Ca+2 absorption. Only 5(Z) 10-oxo-D3 induced mobilization of bone Ca+2. In addition, both 10-oxo-D3 and 25-OH-10-oxo-D3 showed poor affinities for either the plasma D3-binding protein or the thymus 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] receptor. 10-Keto-D3 exhibited a plasma half-life of only 6 min. This was a much shorter half-life than that exhibited by other vitamin D metabolites and was expected because of the poor affinity 10-oxo-D3 has for the plasma vitamin D binding protein. Bacterial metabolism of D3 deactivates the vitamin, which allows ruminants to tolerate relatively large oral doses of D3.
authors.affiliation: National Animal Disease Center, U.S. Department of Agriculture, Ames, IA 50010.
authors.forename: R M
authors.initials: RM
authors.lastname: Gardner
authors.forename: T A
authors.initials: TA
authors.lastname: Reinhardt
authors.forename: R L
authors.initials: RL
authors.lastname: Horst
mesh_terms: D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002762:Cholecalciferol / Q000096:biosynthesis* / Q000494:pharmacology; D007408:Intestinal Absorption / Q000187:drug effects; D007700:Kinetics; D008297:Male; D051381:Rats; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000187:drug effects / Q000378:metabolism; D012417:Rumen / Q000382:microbiology*; D013329:Structure-Activity Relationship
chemical_list: D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D002762:Cholecalciferol; D002118:Calcium