ACTION OF VITAMIN D DEFICIENCY ON BONE TISSUE AND EPIPHYSEAL PLATE IN RATS GIVEN ADEQUATE AMOUNTS OF CALCIUM AND PHOSPHORUS IN DIET

The action of vitamin D on the histological appearance of bone tissue and the epiphyseal plate cartilage was studied in young rats fed a diet containing adequate amounts of calcium and phosphorus. The purpose of the investigation has been to see if vitamin D deficiency had a direct action on bone and cartilage or whether its action was secondary to changes in serum Ca and serum P accompanying vitamin D deficiency. The Ca × P product was probably above the minimum value considered necessary for mineralization. The histological investigation demonstrated some deviations from the normal in the epiphyseal plate of the vitamin D-deficient rats. Whereas the femoral plate thickness in every case was normal, that of the tibia varied from normal to a marked widening. The internal and external morphology of the bones did not deviate much from the normal. The microradiographs showed that mineralization of bone tissue and cartilage had taken place as expected in the vitamin D-deficient rats. However, in some places in the hypertrophied cartilage, corresponding to the expanded regions, a delay in the process of mineralization was found. Beneath such areas some disorganization of the metaphyseal trabeculae was observed. Both osteoblasts and osteoclasts were observed in seemingly normal functional states. No accumulation of osteoid or other abnormal features could be observed in the bone tissue. It may be concluded that the histological and radiological methods applied in the present investigation did not reveal any differences between bone tissue from vitamin D-treated and vitamin D-deficient rats. However, changes were found in the epiphyseal plates in some of the tibiae, indicating a delay in the process of mineralization of the hypertrophic cartilage. It is reasonable to assume that this limited deviation from the normal may be a direct effect of vitamin D deficiency on the cartilage, and not mediated through changes in serum Ca or serum P. © 1969.