ISSN:
1432-0827
Keywords:
1,25-Dihydroxyvitamin D3
;
25-Hydroxyvitamin D3
;
24,25-Dihydroxyvitamin D3
;
Receptors
;
Bone
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
,
Physics
Notes:
Summary The hormonal metabolite of vitamin D3, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], exerts its biological effects by binding to a cytosolic receptor protein. Such a protein has been demonstrated in vitamin D3 target organs including fetal rat calvariae and more recently in rat osteogenic sarcoma cells. In this study we have compared the binding of 25-hydroxyvitamin D3 [25(OH)D3] and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] to that of 1,25-(OH)2D3 in fetal rat calvariae and osteogenic sarcoma (OS) cells. Sucrose density sedimentation, DNA-cellulose chromatography, and intracellular uptake studies have been employed to evaluate these interactions. In cytosol preparations from calvariae, [3H]-1,25(OH)2D3 bound to a 3.3S macromolecule and to a much greater extent to a 5.8S macromolecule while both [3H]25(OH)D3 and [3H]24,25(OH)2D3 bound to the 5.8S macromolecule. By incubating intact calvariae and OS cells with labeled metabolites and thus establishing binding intracellularly prior to cell disruption, we have found that the 3.3S protein which has high specificity for 1,25(OH)2D3 occurs inside the cells; the 5.8S protein, however, does not occur inside the cells but is generated after cell disruption. The [3H]-1,25(OH)2D3-receptor complex adsorbed to DNA-cellulose and was eluted from this affinity resin at 0.28M KCl. In contrast, [3H]25(OH)D3 and [3H]-24,25(OH)2D3 binding activity did not adsorb to DNA-cellulose. We conclude that, in contrast to the 3.3S protein, the 5.8S macromolecule does not fulfill receptor criteria but is rather generated by the experimental manipulation of the bone cells. Our data suggest that the vitamin D3 actions on bone are mediated only via the 3.3S receptor, and hence quantitative but not qualitative differences of the effects of the various metabolites are feasible.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02409504
Permalink
