Bone specific binding sites for 1,25(OH)2D3 in magnesium deficiency.
It has been reported that some hypoparathyroid patients with magnesium deficiency showed altered responses to vitamin D treatment. In the same way, in vitro bone studies have demonstrated the existence of a decrease in the 1,25-dihydroxyvitamin D3-induced resorption in bone as a result of magnesium deficiency. These findings suggest some kind of alteration in the 1,25(OH)2D3 in bone in magnesium deficiency. In the present work, using a binding assay based on the 1,25(OH)2D3 and 3H-1,25(OH)2D3 competition for the hormone binding sites in rat calvaria homogenates, a significant decrease in the number of 1,25(OH)2D3 specific binding sites has been found in calvaria incubated in magnesium-deficient medium compared to magnesium-replete ones. Alterations in the hormone-receptor affinity were not found. These results suggest that an alteration in the 1,25(OH)2D3 action on magnesium-deficient bone could be due, at least in part, to a decrease in the number of available vitamin D receptors in bone cells.
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Laboratorio de Bioquímica, Sección de Fisiopatologia Osea, Fundación Jiménez Díaz, Avda Reyes Católicos 2, 28040 Madrid, Spain.
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D000818:Animals; D001665:Binding Sites; D001842:Bone and Bones / Q000378:metabolism*; D002117:Calcitriol / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D005333:Fetus; D008275:Magnesium Deficiency / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018167:Receptors, Calcitriol / Q000096:biosynthesis; D012886:Skull
D018167:Receptors, Calcitriol; D002117:Calcitriol; D002118:Calcium