The effect of low calcium diet on bone in ovariectomized mice

This study investigates the effects of Ca on bone in the ovariectomized mice. Twenty-six female ICR mice aged 5 weeks were used. They were ovariectomized (OVX) or sham-operated (SHAM) and fed standard mouse diet (SF) or special low calcium diet (L.Ca), respectively. All animals were sacrificed at day 100 after operation. Mechanical strength of the left femur and tibia was measured by the three-point bending strength test. The bones were dried, weighed and burned to ash. Correlation between mechanical strength and ash content was found. A specimen of the right tibia was prepared. Mechanical strength, ash content and ratio of dry bone weight to body weight of the femur and tibia in OVX and L.Ca mice were significantly less than in SHAM and SF mice. SHAM/SF mice and OVX/L.Ca group showed highest and lowest values in all cases. The values for the femur and tibia in OVX/SF mice were lower than in SHAM/SF group and in OVX/L.Ca group were less than in OVX/SF mice. Correlation coefficients for mechanical strength and ash content were 0.704 and 0.776 for the femur and tibia. Ca is thus related to inhibition of bone loss and maintenance of bone mass and effective prevention of osteoporosis.