QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vieth, R. Articles by Peltekova, V. Search for Related Content PubMed PubMed Citation Articles by Vieth, R. Articles by Peltekova, V.

---

Article

Improved Cholecalciferol Nutrition in Rats Is Noncalcemic, Suppresses Parathyroid Hormone and Increases Responsiveness to 1,25-Dihydroxycholecalciferol¹

Departments of Pathobiology and Laboratory Medicine, University of Toronto and Mount Sinai Hospital, Toronto, Ontario, M5G 1X5 Canada

²To whom correspondence should be addressed.

We examined how cholecalciferol (vitamin D) nutrition affected serum 25-hydroxycholecalciferol (25(OH)D) and 1,25-dihydroxycholecalciferol (1,25(OH)₂D). Rats were fed conventional diet (vitamin D, 4.5 IU/g, or 7 nmol/d) or the same diet plus 18 nmol/d of extra vitamin D for 3 wk. The extra vitamin D resulted in greater serum 25(OH)D (51 ± 3, vs. control of 21 ± 2 nmol/L), and kidney mRNA for vitamin D receptor [VDR mRNA] (P = 0.026) and lower serum 1,25(OH)₂D (72 ± 16 vs. control of 161 ± 10 pmol/L, P = 0.001), and parathyroid hormone (PTH) (89 ± 4 vs. control of 160 ± 15 ng/L, P = 0.001). Kidney VDR mRNA relative to GAPDH mRNA correlated inversely with serum 1,25(OH)₂D (r = -0.714, P = 0.006). There were no differences in serum calcium, phosphate, alkaline phosphatase, or weight gain. Experiment 2 compared groups supplemented with 0.2, 2 or 20 nmol/d of vitamin D orally, or 20 nmol/d dermally to see how vitamin D nutrition influenced the response of 1,25(OH)₂D to changes in diet calcium. Vitamin D did not affect urinary calcium or pyridinoline excretion, serum calcium, phosphate, vitamin D binding protein or alkaline phosphatase. In groups given 20 nmol/d of vitamin D, renal mitochondrial 25(OH)D-1-hydroxylase was lower (P < 0.01) and 25(OH)D-24-hydroxylase was higher (P < 0.05). Higher 25(OH)D concentration was related to proportionally lower 1,25(OH)₂D at every calcium intake, indicating greater tissue sensitivity to 1,25(OH)₂D. We conclude suppression of 1,25(OH)₂D and PTH, and higher renal VDR mRNA and 24-hydroxylase did not involve higher free 1,25(OH)₂D concentration or a first pass effect at the gut. Thus, 25(OH)D or a metabolite other than 1,25(OH)₂D is a physiological, transcriptionally and biochemically active, noncalcemic vitamin D metabolite.

KEY WORDS: • vitamin D • calcium • adaptation • parathyroid hormone • rats • transcription

This article has been cited by other articles:

				J. C. Fleet, C. Gliniak, Z. Zhang, Y. Xue, K. B. Smith, R. McCreedy, and S. A. Adedokun Serum Metabolite Profiles and Target Tissue Gene Expression Define the Effect of Cholecalciferol Intake on Calcium Metabolism in Rats and Mice J. Nutr., June 1, 2008; 138(6): 1114 - 1120. [Abstract] [Full Text] [PDF]

				J. C. McCann and B. N. Ames Is there convincing biological or behavioral evidence linking vitamin D deficiency to brain dysfunction? FASEB J, April 1, 2008; 22(4): 982 - 1001. [Abstract] [Full Text] [PDF]

				R. M. Leach Jr. and E. Monsonego-Ornan Tibial Dyschondroplasia 40 Years Later Poult. Sci., October 1, 2007; 86(10): 2053 - 2058. [Abstract] [Full Text] [PDF]

				S. M Kimball, M. R Ursell, P. O'Connor, and R. Vieth Safety of vitamin D3 in adults with multiple sclerosis Am. J. Clinical Nutrition, September 1, 2007; 86(3): 645 - 651. [Abstract] [Full Text] [PDF]

				M. A. Tryfonidou, M. A. Oosterlaken-Dijksterhuis, J. A. Mol, T. S. G. A. M. van den Ingh, W. E. van den Brom, and H. A. W. Hazewinkel 24-Hydroxylase: potential key regulator in hypervitaminosis D3 in growing dogs Am J Physiol Endocrinol Metab, March 1, 2003; 284(3): E505 - E513. [Abstract] [Full Text] [PDF]

				R. Vieth, Y. Ladak, and P. G. Walfish Age-Related Changes in the 25-Hydroxyvitamin D Versus Parathyroid Hormone Relationship Suggest a Different Reason Why Older Adults Require More Vitamin D J. Clin. Endocrinol. Metab., January 1, 2003; 88(1): 185 - 191. [Abstract] [Full Text] [PDF]

				R. Vieth Vitamin D ingestion and changes to rat aorta Cardiovasc Res, November 1, 2002; 56(2): 323 - 324. [Full Text] [PDF]

				M. A. Tryfonidou, J. J. Stevenhagen, G.J.C.M. van den Bemd, M. A. Oosterlaken-Dijksterhuis, H. F. DeLuca, J. A. Mol, W. E. van den Brom, J.P.T.M. van Leeuwen, and H.A.W. Hazewinkel Moderate Cholecalciferol Supplementation Depresses Intestinal Calcium Absorption in Growing Dogs J. Nutr., September 1, 2002; 132(9): 2644 - 2650. [Abstract] [Full Text] [PDF]

				R. Vieth Reply to FAJ Muskiet et al Am. J. Clinical Nutrition, December 1, 2001; 74(6): 863 - 864. [Full Text]