Estrogen-induced sequential changes in avian bone metabolism

Medullary bone was induced in male Japanese quail by administration of estradiol valerate. An increase in the organic weight of the femur was observed by 36 h after estrogen and an increase in ash weight was observed by 96 h. A complex sequence of metabolic changes in the femur occurred after estrogen treatment. A large increase in uptake of 3H-proline associated with enhanced collagen formation began 36 h after estrogen and reached a peak 3.5 times the control rate at 60 h. The onset of mineralization of the newly formed bone matrix, as determined by 45Ca uptake, began about 24 h after onset of collagen synthesis indicating that synthesis of the bone matrix and its mineralization occur sequentially. Large increases in the rates of uptake of 3H-uridine and 3H-thymidine occurred prior to the onset of medullary bone formation and appear to reflect the differentiation of osteogenic precursors to bone-forming cells.