Title: Abnormal Vitamin D Metabolism in the X-Linked Hypophosphatemic Mouse*
Abstract: The vitamin D metabolites, 25-hydroxyvitamin D (250HD) and 1,25-dihydroxyvitamin D [1,25-(OH)2D], were measured in samples of plasma from normal and X-linked hypophosphatemic (Hyp) mice, which are a model for this common form a human vitamin D-resistant rickets. Each sample was the pooled plasma from the exsanguination of 10-15 mice. On stock diets plasma 1,25-(OH)2D was the same in Hyp mice as in normal mice [normal vs. Hyp, 70 +/- 4 vs. 66 +/- 4 pM; (mean +/- SE) n = 8; P = NS]. However, plasma 25OHD was lower in Hyp mice (59 +/- 4 vs. 37 +/- 4 nM; n = 6; P < 0.01). Since hypophosphatemia usually elevates plasms 1,25-(OH)2D in rats, we suspected that Hyp mice were unresponsive to hypophosphatemia. To test this, mice were challenged with a low phosphorus (P) diet for 6 days . A low P diet lowered plasma P and raised plasma calcium levels in both normal and Hyp mice. In both genotypes, the low P diet also increased magnesium levels in urine and transiently in plasma. The low P diet raised plasma 1,25-(OH)2D in normal mice, but lowered it in Hyp mice to nondetectable levels. There was no significant effect of the low P diet on plasma levels of 25OHD. We conclude that Hyp mice have a defective control system for plasma levels of 1,25-(OH)2D that does not respond to a low P stimulus with elevated plasma levels of the hormone.
Publication Year: 1980
Publication Date: 1980-11-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 118
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