[Effect of vitamin D3 and its metabolites 1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol on callus mineralization in rats with femoral fracture]

Abstract

Additional administration of vitamin D3 at a physiological dose of 0.25 microgram daily into rats with femur fracture within 4 weeks did not affect the specific weight and chemical composition (content of Ca2+, P) in diaphyses of intact and impaired femurs as well as the content of Ca2+. Pi and activity of alkaline phosphatase in blood serum of the animals. At a higher dose 2.5 microgram daily vitamin D3 increased concentration of Pi in blood serum but did not alter the other parameters studied. Physiological doses of 1,25-dihydroxycholecalciferol (1.25 (OH)2D3) and 24,25-dihydroxycholecalciferol (24,25 (OH)2D3) (00.3 microgram and 0.25 microgram daily, respectively) did not affect the specific weight and composition of the impaired diaphyses, content of Ca2+ and activity of alkaline phosphatase in blood but increased slightly the Pi concentration. After a 5-fold increase in the dose of 1,25(OH)2D3 (0.15 microgram daily) specific weight and content of Ca2+ were decreased in the impaired bones with simultaneous increase in concentration of Ca2+, Pi and activity of alkaline phosphatase in blood serum. These data suggest that reparation was impaired under the conditions of acceleration of the bone tissue resorption. Increased doses of 24, 25(OH)2D3 (1.25 micrograms daily) stimulated the increase in specific weight and mineralization of the impaired bones and normalized the increased alkaline phosphatase activity in blood serum. Clinical examination of 24,25(OH)2D3 could be recommended as a drug stimulating the reparation under conditions of bone fracture.