Phosphatase Activity of the Serum and Tissues in Osteogenesis Imperfecta

Robison 1 has pointed out that the enzyme phosphatase is an important factor in the calcification of bone. Kay 2 has more recently summarized the evidence for its activity in connection with studies on a wide variety of clinical conditions. Since osteogenesis imperfecta is an outstanding example of defective bone formation for which no pathogenesis has as yet been discovered, a comprehensive study of the various metabolic factors which might be involved in this condition was begun by the writer in 1931. The present report deals with the phase of that study which concerns the phosphatase activity of the blood serum and fixed tissues.

Kay reported the serum phosphatase activity to be slightly increased in some cases of osteogenesis imperfecta, while Bodansky and Jaffe 3 found it to be normal in 6 cases.

Periodic determinations of the serum phosphatase by the method of Kay have now been made in 4 cases of osteogenesis imperfecta under a variety of experimental conditions. In one case the fixed tissue phosphatase has also been studied postmortem.

Repeated determinations in the 4 cases showed values almost identical with those found for normal control subjects and for a miscellaneous group of patients in the same age period. Variations in the ordinary constituents of the diet were found to have no definite effect on the serum phosphatase values. Following the administration of vitamin D in relatively enormous doses in the form of viosterol 10,000X, however, the phosphatase activity of the serum was uniformly reduced. Parathormone administration over a period of several days had a similar but less marked depressing effect on the enzyme.