Effects of drug treatment on bone strength and structural changes with aging: an experimental study in rats.

The purpose of the present study was to evaluate the profiles of the bone strength of rats treated from infancy with various drugs. Young female Sprague-Dawley rats were classified into five groups according to the composition of their diets. They underwent resection of their femurs for a three-point flexion test and an impaction test at 6, 8, 12, and 16 months of age. A microcomputed tomography unit was used to evaluate the microstructure of their femoral condyles at 16 months of age. The diet given to the rats in the control group contained 0.5% Ca. The rats in groups A, B, C, and D were placed on the following regimens, respectively: vitamin K mixed diet, vitamin D oral administration, 1.8% Ca-fortified diet, and 1.8% Ca-fortified diet plus vitamin K and vitamin D. In the impaction tests conducted on the rats at each age, the results from groups A and B were nearly the same as those from the control group. At 16 months of age, the rats in groups C and D had significantly higher test results than those in the control group. In the three-point flexion tests at 16 months of age, the results from groups A, B, and C were nearly the same as those from the control group. The results from group D, however, showed a significant increase. Examination of the microstructure of the femoral condyles at 16 months of age revealed controlled destruction of the trabecular structure in groups C and D. These findings suggest that supplementing the diet from infancy with Ca, vitamin K, and vitamin D might prevent bone fractures due to osteoporosis.