| First Author | Roy S | Year | 1994 |
| Journal | Endocrinology | Volume | 134 |
| Issue | 4 | Pages | 1761-7 |
| PubMed ID | 8137741 | Mgi Jnum | J:17591 |
| Mgi Id | MGI:65625 | Doi | 10.1210/endo.134.4.8137741 |
| Citation | Roy S, et al. (1994) Increased renal 25-hydroxyvitamin D3-24-hydroxylase messenger ribonucleic acid and immunoreactive protein in phosphate-deprived Hyp mice: a mechanism for accelerated 1,25-dihydroxyvitamin D3 catabolism in X-linked hypophosphatemic rickets. Endocrinology 134(4):1761-7 |
| abstractText | X-Linked Hyp mice exhibit rachitic bone disease, hypophosphatemia, impaired renal phosphate reabsorption, and abnormal regulation of renal 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] metabolism. We demonstrated that phosphate deprivation of Hyp mice, but not normal littermates, elicits a dramatic fall in serum 1,25-(OH)2D levels and an increase in renal 1,25-(OH)2D3 catabolism that can be ascribed to an increase in the activity of renal mitochondrial 25-hydroxyvitamin D3-24-hydroxylase (24-hydroxylase), the first enzyme in the C-24 oxidation pathway. The present study was undertaken to elucidate the mechanism for the increase in renal 24-hydroxylase activity in phosphate-deprived Hyp mice. Phosphate deprivation of Hyp mice resulted in a 3-fold increase in the maximum velocity for 24-hydroxylase (n = 5; P < 0.001) accompanied by an increase in 24-hydroxylase immunoreactive protein relative to the level of ornithine aminotransferase. Phosphate deprivation of Hyp mice also elicited a 3-fold increase in renal 24-hydroxylase mRNA abundance relative to that of beta-actin mRNA (n = 7; P < 0.001). The increase in 24-hydroxylase mRNA was specific to the kidney and was evident as early as 1 day of the low phosphate diet. Phosphate deprivation had no effect on renal 24-hydroxylase immunoreactive protein or mRNA in normal littermates. In contrast to the abnormal 24-hydroxylase response to dietary phosphate, Hyp mice exhibited an appropriate increase in renal 24-hydroxylase mRNA and catalytic activity in response to increasing doses of 1,25-(OH)2D3. The present results demonstrate that elevated renal 24-hydroxylase activity in phosphate-deprived Hyp mice can be ascribed to an increase in the abundance of 24-hydroxylase mRNA and protein and suggest that inappropriate regulation of 1,25-(OH)2D3 catabolism in Hyp mice occurs at the pretranslational level. |
