Changes in alkaline phosphatase activity in periosteal cells in healing fractures.

The quantitative changes in alkaline phosphatase activity in the periosteal cells close to the fracture in rat metatarsal bones has been measured during the first 5 days postfracture. This study has been made possible by two technological advances, firstly the development of cryostat microtomy for cutting unfixed, undemineralised bone, and secondly the use of scanning and integrating microdensitometry for quantifying the activity in each periosteal cell. The results showed a loss of alkaline phosphatase activity close to the fracture site, with activity rising to normal values 0.8-1.0 mm from the site. No alkaline phosphatase activity was found in the cells which proliferated from the periosteum. It is suggested that reduced glutathione could cause such inhibition.