The effect of hypervitaminosis D on the bone of the albino rats has been studied. The following results have demonstrated:
A) Histological Changes : In stage of 14-days old, the periosteum becomes more thicker, vascu larized and the number of osteoblasts and osteocytes are increased. Some osteocytes become swollen and showed pyknotic nuclei in stage of 21-days old. At the age of 28-days old, the bone having the appea rance of a compact bone more than being cancellous unlike the control group, and the proportion between the bone substances and marrow cavities is elevated. The collagenous fibers are markedly increased in the periosteum and in the bone matrix at the ages of 21 and 28-days old.
In adult stages, excessive doses of vitamin D cause other changes in the bone. The osteocytes become more elongated with narrow lucunae. The number of Haversian systems is decreased. The collagenous meterial is increased than that of the normal.
B) Histochemical Changes :
The carbohydrate content in the bones of postnatal and adult stages is not affected, while the proteinic content is increasd in all stages.
C) Physiological Changes : The amount of calcium in bone-ash and serum is increased than normal.