Male Holtzman rats were fed large doses of vitamin A, D or A and D for 43 days. Sections of the tibia demineralized in EDTA were submitted to alpharadiography or stained by a variety of procedures, including mucopolysaccharide histochemistry. The results were as follows:

  • (1)
    In hypervitaminosis D, slightly increased periosteal apposition of normal bone; greatly increased maturation of osteocytes with lacunar enlargement and confluence, interstitial metachromasia and loss of density (osteocytic osteolysis).
  • (2)
    In hypervitaminosis A, large growth of abnormally stained cancellous bone at periosteum and stimulation of osteolysis in new and old bone.
  • (3)
    In combined A and D hypervitaminoses, the peripheral apposition rate exceeded that induced by vitamin A or vitamin D alone. The new bone appeared fragile and this combined with increased osteolysis was responsible for a number of spontaneous fractures.