Print Email Facebook Twitter Moderate cholecalciferol supplementation depresses intestinal calcium absorption in growing dogs Title Moderate cholecalciferol supplementation depresses intestinal calcium absorption in growing dogs Author Tryfonidou, M.A. Stevenhagen, J.J. van den Bemd, G.J.C.M. Oosterlaken-Dijksterhuis, M.A. Deluca, H.F. Mol, J.A. van den Brom, W.E. van Leeuwen, J.P.T.M. Hazewinkel, H.A.W. Centraal Instituut voor Voedingsonderzoek TNO Publication year 2002 Abstract Hormonal regulation of calcium (Ca) absorption was investigated in a cholecalciferol (vitamin D3)supplemented group (hVitD) vs. a control group (cVitD) of growing Great Danes (100 vs. 12.5 μg vitamin D3/kg diet). Although Ca intakes did not differ, fractional Ca absorption was significantly lower in the hVitD group than in the cVitD group. There were no differences in plasma concentrations of Ca, inorganic phosphate, parathyroid hormone, growth hormone or insulin-like growth factor I between groups. Plasma 25-hydroxycholecalciferol [25(OH)D3] concentrations were maintained in the hVitD dogs at the same levels as in the cVitD dogs due to increased turnover of 25(OH)D3 into 24,25-dihydroxycholecalciferol [24,25(OH)2D3] and 1,25-dihydroxycholecalciferol [1,25(OH)2D3]. In hVitD dogs, the greater plasma 24,25(OH)2D3 concentration and the enhanced metabolic clearance rate (MCR) of 1,25(OH)2D3 indicated upregulated 24-hydroxylase activity. The increased MCR of 1,25(OH)2D3 decreased plasma 1,25(OH)2D3 concentrations. In hVitD dogs, the greater production rate of 1,25(OH)2D3 was consistent with the 12.9-fold greater renal 1 α-hydroxylase gene expression compared with cVitD dogs and compensated to a certain extent for the accelerated MCR of 1,25(OH)2D3. The moderately decreased plasma 1,25(OH)2D3 concentration can only partially explain the decreased Ca absorption in the hVitD dogs. Intestinal vitamin D receptor concentrations did not differ between groups and did not account for the decreased Ca absorption. We suggest that 24,25(OH)2D3 may downregulate Ca absorption. Chemicals/CAS: 25-Hydroxyvitamin D3 1-alpha-Hydroxylase, EC 1.14.-; Calcitriol, 32222-06-3; Calcium Radioisotopes; Calcium, 7440-70-2; Calcium, Dietary; Cholecalciferol, 67-97-0; Cytochrome P-450 Enzyme System, 9035-51-2; Phosphates; Receptors, Calcitriol; Steroid Hydroxylases, EC 1.14.-; vitamin D 24-hydroxylase, EC 1.14.- Subject NutritionAnimalsCalcitriolCalciumCalcium RadioisotopesCalcium, DietaryCholecalciferolCytochrome P-450 Enzyme SystemDogsDown-RegulationFemaleGene Expression Regulation, EnzymologicIntestinal AbsorptionIntestinesKidneyMaleMetabolic Clearance RateModels, AnimalPhosphatesReceptors, CalcitriolSteroid HydroxylasesAnimaliaCanis familiaris To reference this document use: http://resolver.tudelft.nl/uuid:d461650e-4c87-4064-999f-651c8a6e605a TNO identifier 88038 ISSN 0022-3166 Source Journal of Nutrition, 132 (9), 2644-2650 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.