Abnormal 24-hydroxylation of 25-hydroxyvitamin d in the x-linked hypophosphatemic mouse

John Cunninghams, Holly Gomes, Yoshiki Seino, Lewis R. Chase

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


The effect of extracellular phosphate on the control of 25-hydroxyvitamin D3 24-hydroxylase was studied in normal mice and littermates with X-linked hypophosphatemic rickets (Hyp). 24-Hydroxylase activity and plasma concentrations of 24, 25-dihydroxyvitamin D3 were significantly higher in Hyp mice than in normal mice when both groups were fed a normal diet containing 1.22% calcium (Ca) and 0.8% phosphorus (Pi). The differential in 24-hydroxylase activity was exaggerated when serum phosphate was reduced in normal mice by means of a low Pi diet or increased in Hyp mice by means of a high Pi diet. Differences in 24-hydroxylase activity between the two groups of mice were also demonstrated in the presence of varying Pi concentrations in vitro. Thus, in both Hyp and normal mice, 24-hydroxylase activity is influenced in a qualitatively similar manner by serum Pi. Plasma concentrations of 1, 25-dihydroxyvitamin D3 were the same in normal and Hyp mice. The data are consistent with the hypothesis that control of the renal metabolism of 25-hydroxyvitamin D3 in Hyp mice is reset such that 24-hydroxylase activity is inappropriately high for the prevailing serum phosphate over a wide range of concentrations.

Original languageEnglish
Pages (from-to)633-638
Number of pages6
Issue number2
StatePublished - Feb 1983


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