Effective intervention of low peak bone mass and bone modeling in the spontaneous murine model of senile osteoporosis, SAM-P/6, by Ca supplement and hormone treatment.

SAM-P/6 is a recently developed strain of osteoporotic mice. In this study we tried to determine whether calcium, vitamin D3, parathyroid hormone (PTH), and estrogen modified the peak bone mass of young SAM-P/6 mice, and whether the effect of these medications persisted after treatment had been discontinued. Calcium supplement, PTH, and estrogen treatment increased the peak bone mass of SAM-P/6 mice. To clarify the process by which bone mass was increased in these treated mice, we evaluated their bone formation and resorption by histomorphometry and measured the levels of ions and serum enzymes relevant to bone metabolism. We found that bone formation was increased by calcium supplementation, and bone resorption was decreased by estrogen treatment. Furthermore, the effectiveness of calcium supplement on peak bone mass was retained after treatment had been discontinued, but the effect of estrogen treatment on peak bone mass was reduced after estrogen treatment had been discontinued. The results of this study indicate that calcium supplementation and estrogen and PTH treatment each increased peak bone mass at the midpoint of the femur of SAM-P/6, and that the effect of calcium supplementation, but not that of estrogen treatment, persisted after treatment was discontinued.