Influence of 1 alpha-hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 on experimentally induced heterotopic ossification in rats.

We report the effects of 1 alpha-OH-D3 and 24,25(OH)2D3, either alone or combined, on new bone formation induced by demineralized cortical bone matrix transplanted extraskeletally to the abdominal muscle wall in rats. 1 alpha-OH-D3 was administered orally in dosages of 0.1 microgram, 24,25(OH)2D3 in dosages of 0.2 micrograms, and, in the combined procedure, in the same dosages as mentioned above per day and rat. The amount of induced new bone in respect of organic matter, mineral content and 45Ca activity increased in all treatment groups, compared with controls. The differences between the groups treated separately with 1 alpha-OH-D3 or 24,25(OH)2D3 were insignificant. The differences in the combined treatment group were not so profound, but differed considerably compared with controls. However, 1 alpha-OH-D3 showed more prominent effects on the mineralization of implanted grafts, while 24,25(OH)2D3 especially promoted the production of organic material of the newly formed bone.