Role of vitamin D in neonatal skeletal development in rats.

The role of vitamin D in rat pup growth and skeletal development without the influence of nutritional factors was investigated. Pups from vitamin D-replete and vitamin D-deficient dams receiving identical amounts of milk for 20 days were compared. Body weight gain, femur ash content and histomorphometric analyses of diaphysial and distal femur were determined. Up to 20 days of age, growth and skeletal development of the pups were completely normal in the absence of vitamin D. Skeletal changes found in vitamin D deficiency were not observed, i.e., there was no increased volume of osteoid or lack of bone mineralization as demonstrated by tetracycline labeling and ash content. Only increased cortical porosity was found in vitamin D-deficient pups. Therefore, abnormalities previously attributed to vitamin D deficiency in neonatal rats can be corrected by sufficient milk consumption and are thus not a direct function of vitamin D.