Effect of Ovariectomy and Calcium Intake on Femur and Lumbar Compositions and Bone Related Factors in Adult Rats

성숙한 쥐의 대퇴골과 요추의 조성과 골격관련 인자에 대한 난소절제와 칼슘섭취 효과

This study explored the effect of calcium levels and/or ovariectomy on bone composition and its related factors using the female Sprague-Dawley rats which achieved peak bone mass in normal(0.5%) calcium intake during growth period. The rats were randomly divided into six groups and fed 0.1%, 0.5% and 1.5% calcium diets for 8 weeks after ovariectomized and sham operation. The results indicated that body weight gain was higher in ovariectomized groups than sham groups, regardless of dietary calcium levels and food intakes. Serum Ca and P concentrations were normal level regardless of dietary calcium levels and operation. Estrogen concentration was decreased in ovariectomized rat groups. Serum alkaline phosphatase activity and urinary hydroxyproline were increased in ovariectomized groups. When rats were fed normal Ca diet during growing period, weight, length and breaking force of femur were not significantly different in all groups but increased the same level. Generally, lipid contents in lumbar and femur were lower in low calcium groups and this effect was more pronounced in femur. In case of femur, the significant decrease in Ca contents of bone was observed in a relatively short period of feeding low Ca diet, even though it appeared th desirable peak bone mass had achieved through the growing period by supplementing the adequate amount of calcium. The marked decrease of estrogen levels after ovariectomy did not seem to influence greatly bone parameters measured except bone wet weight. Therefore, this study indicated that lower intake of Ca might be more important determinating factor against osteoporosis than postmenopausal state stimulated by ovariectomy in female rats. With normal or high intake of Ca it appears possible to prevent bone loss in postmenopausal period, and this might apply only in case of achieving peak bone mass in the growing with the adequate intake of calcium. (Korean J Nutrition 34(5) : 532∼540, 2001)