Effect of 1 alpha-hydroxyvitamin D3 on cancellous bone matrix. An experimental study on adult rats.

Two groups of adult male rats were treated perorally for 6 weeks with 0.1 microgram and 1.0 microgram of 1a-hydroxyvitamin D3 (1a-OH-D3), respectively. The effect of the treatment on cancellous bone matrix was studied by chemical analysis and morphometric measurements. The effect of the 1.0 microgram dose on the inorganic composition, and on the calcification of the cancellous bone matrix, was significantly more pronounced, decreasing the amount of glycosaminoglycans. The lower dose level, 0.1 microgram of 1a-OH-D3, increased the collagen metabolism, whereas the higher dose level did not. The amount of cancellous bone determined morphometrically increased significantly during treatment with both dose levels. 1a-OH-D3, converted in the organism to the hormonal form 1.25 (OH)2D3, induces new bone formation, probably by direct influence on the cancellous bone tissue itself.