Investigations of alkaline phosphatase Ca+2-ATPase and Na+, K+-ATPase during beta-APN-induced initial bone mineralization inhibition.

Tibias of 6-day-old white Leghorn chick embryos treated with beta-aminopropionitrile (beta-APN; 0.1 mg/egg/day) for 4 days and injected with 3H-proline or 3H-tetracycline on the 11th day were analyzed for incorporation of 3H-proline and 3H-tetracycline. The incorporation of 3H-proline was comparable in the controls and beta-APN-treated embryos. However, the incorporation of 3H-tetracycline was significantly lower in beta-APN-treated embryos. The bone ash contents were also lower in the latter group. Alkaline phosphatase and Ca+2-ATPase were found to be significantly lower in beta-APN-treated embryonic bones. There was, however, no difference in the activity of Na+, K+-ATPase. The histochemical examination showed the alkaline phosphatase to be present on osteoblasts and matrix vesicle plasma membranes at the periosteal surface. The chick embryonic liver tissue showed no significant differences in the activities of any of the above enzymes. The results suggest that beta-APN-induced inhibition of the bone mineralization may be due to the bone-specific inhibition of alkaline phosphatase and Ca+2-ATPase.