Changes in alkaline phosphatase activity in periosteal cells in healing fractures

Abstract

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.

Metabolic changes in the cells of the callus during fracture healing in the rat

“…Serial sections were then stained with Alcian blue for demonstrating the glycosaminoglycan content or reacted for the cytochemical demonstration of alkaline phosphatase and of G6PD. The reaction medium for the demonstration of alkaline phosphatase activity [2] contained a 10% solution of magnesium chloride (0.2 ml): naphthol-phosphate sodium salt (2 mg, Sigma): Fast blue RR salt (50 rag, G. T. Gurr) in 50 ml of a 2% solution of 5,5 diethylbarbiturate. The pH was adjt, sted to 9.4.…”

“…However, it has been shown [1,2] that the early changes in the activities of two enzymes in one of these populations of cells, namely, the periosteal cells, can be defined by means of cytochemical reactions measured microdensitometrically. The cytochemical procedures result in a colored reaction-product being deposited in the active cells; these are defined histologically, and the amount of colored reaction-product in each histologically defined cell is measured by means of a microdensitometer.…”

The effect of zinc on alkaline phosphatase activity in rheumatoid synovial tissue.

“…This phenomenon was not confused by sampling error caused by the vascularity of the areas sampled because it applied even when the activity of the vessels alone was measured ( Table 2). The enzyme has zinc at its active site (Ahlers, 1975) and it can be inhibited by substances, such as reduced glutathione, that bind to zinc (Ahlers, 1975;Shedden et al, 1976). Thus it is possible that the alkaline phosphatase activity of rheumatoid synovial tissue is partially suppressed by such molecules and can be freed from such inhibition by exogenous zinc.…”

Concerning the possibility of redox drugs

“…A high ratio of NADPH : NADP + can induce the reduction of glutathione, leading to a high ratio of the reduced glutathione'oxidized glutathione couple which could have implications in the healing of fractures [16] and possibly of wounds generally. It would also influence the sulphydryl : disulphide couple of cytoplasmic proteins.…”