1970 Volume 7 Issue 6 Pages 342-350
The inhibitory effect of estrogens on the development of immobilization osteoporosis in rat was studied through the analysis of calcium and hydroxyproline content of the femur and tibia, and the measurement of cortical thickness of the femurs. In 6 weeks old rat, immobilization of the right hind limb through the application of a plaster cast for 6 weeks caused a marked decrease in the calcium content of the femur and the hydroxyproline content of the tibia. This decrease, however, was significantly inhibited by the simultaneous oral administration of 100μg of conjugated estrogens. Furthermore, administration of conjugated estrogens significantly protected against the decrease in the bone density and the cortical thickness of the femurs of the immobilized limbs of rats. In 6 month old rats, immobilization of the right hind limb for 8 weeks had no effect. However, after ovariectomy immobilization caused a significant decrease in both calcium and hydroxyproline content of the bones and the cortical thickness of the femurs. Furthermore, these changes were significantly inhibited by the simultaneous administration of conjugated estrogen. It is concluded that conjugated estrogens diminished effect of immobilization on the development of osteoporosis in rat.