A chick bone model for evaluating radial bone growth. 1. Effects of vitamin D3 deficiency

Vitamin D3 is essential for calcification and normal bone development in chicks. In its absence, calcification is reduced but the volume (and mass) of bone increases. In vitamin D3-deficient chicks, this study shows the major defect to be in bone resorption rather than formation. Bone formation measured serially by the apposition of periosteal matrix was normal, whereas bone resorption measured by dissolution at the endosteal surface was dramatically reduced. Bone cells, therefore, would appear to retain their capacity to synthesize a collagenous matrix in the absence of vitamin D3 but lose their capacity to resorb bone. Calcification and its putative dependence on bone resorption (and vitamin D) remain to be elucidated. The vitamin D3-deficient chick provides a convenient and easily quantifiable model in which the morphological and biochemical effects of vitamin D3 can be further studied.