Effect of dichloromethylene diphosphonate on bone metabolism in calcium and phosphorus-depleted rats

In this paper we examine the effects of dichloromethylene diphosphonic acid (Cl2MDP) (1.0 mg P/kg) in rats which have high levels of bone resorption due to the consumption of low-calcium (0.2%) or low-phosphorus (0.2%) diets. Cl2MDP increased the number of osteoclasts as shown by an increased length of resorbing surface but decreased osteoclast activity as measured by the linear rate of bone resorption. These effects appeared to be greater in the low-calcium and low-phosphorus rats, where resorption rates were higher than normal. However, these interactions between dietary and Cl2MDP effects were not statistically significant by analysis of variance. Endosteal bone formation was decreased by Cl2MDP, and the magnitude of this was significantly less in rats receiving low-calcium or low-phosphorus diets where endosteal bone formation was already low. Small but statistically significant decreases were also evident in periosteal bone formation and mineralization parameters in Cl2MDP-treated rats whether on normal or low-calcium or low-phosphorus diets.