| First Author | Safadi FF | Year | 1999 |
| Journal | J Clin Invest | Volume | 103 |
| Issue | 2 | Pages | 239-51 |
| PubMed ID | 9916136 | Mgi Jnum | J:52225 |
| Mgi Id | MGI:1328657 | Doi | 10.1172/JCI5244 |
| Citation | Safadi FF, et al. (1999) Osteopathy and resistance to vitamin D toxicity in mice null for vitamin D binding protein. J Clin Invest 103(2):239-51 |
| abstractText | A line of mice deficient in vitamin D binding protein (DBP) was generated by targeted mutagenesis to establish a model for analysis of DBP's biological functions in vitamin D metabolism and action. On vitamin D-replete diets, DBP-/- mice had low levels of total serum vitamin D metabolites but were otherwise normal. When maintained on vitamin D-deficient diets for a brief period, the DBP-/-, but not DBP+/+, mice developed secondary hyperparathyroidism and the accompanying bone changes associated with vitamin D deficiency. DBP markedly prolonged the serum half-life of 25(OH)D and less dramatically prolonged the half-life of vitamin D by slowing its hepatic uptake and increasing the efficiency of its conversion to 25(OH)D in the liver. After an overload of vitamin D, DBP-/- mice were unexpectedly less susceptible to hypercalcemia and its toxic effects. Peak steady-state mRNA levels of the vitamin D-dependent calbindin-D9K gene were induced by 1,25(OH)2D more rapidly in the DBP-/- mice. Thus, the role of DBP is to maintain stable serum stores of vitamin D metabolites and modulate the rates of its bioavailability, activation, and end-organ responsiveness. These properties may have evolved to stabilize and maintain serum levels of vitamin D in environments with variable vitamin D availability. |
