THE INFLUENCES OF CASEIN PHOSPHOPEPTIDES ON METABOLISM OF ECTOPIC BONE INDUCED BY DECALCIFIED BONE-MATRIX IMPLANTATION IN RATS

The effect of casein phosphopeptides (CPP) on bone metabolism was stud ied in the ectopic bone induced by the implantation of decalcified bon e matrix in rats. Forty-two Wistar male rats of 7 weeks old were fed l ow calcium diets (0.39% of calcium) with or without supplying 0.50% of CPP, or a control diet (0.91% of calcium) without CPP supplementation . After a 1-week preliminary period, each rat was subcutaneously impla nted with 30 mg of demineralized bone matrix powder. Fourteen and 21 d ays after the implantation, the implants were harvested from 7 rats of each group. Calcium content in the graft was not significantly differ ent among all groups on day 14. Subsequently, the content of calcium r apidly increased in the grafts irrespective of diets given. However, t he graft of the CPP- group contained less calcium than the other group s and the calcium content was more in the control rats compared to the CPP+ animals on day 21. Alkaline phosphatase activity (an index of bo ne and cartilage calcification) was lower in the control group than in the CPP+ group on day 14. The enzyme activity subsequently decreased in the control group but the activity was not changed in the other gro ups. As a result, the activity of alkaline phosphatase was lower in th e control animals than in the other rats on day 21. Tartrate-resistant acid phosphatase activity (an index of bone resorption) was higher in the CPP- group compared to the control on day 14. On day 21, the acti vity was higher in the CPP- group compared to the others. Histological study indicated that the number of osteoclastic cells was larger in t he CPP- rats than in the other animals on day 21. These results sugges t that CPP supplementation mitigates the reduction of calcium content in bone of rats fed a low calcium diet and that this action of CPP is due to the suppression of bone resorption, which is involved in the re duction of osteoclast differentiation.