Effects of Irradiation in vitro on Calcifying Mechanism of Epiphyseal Cartilage.

Abstract

A method of toluidine blue staining was devised to demonstrate metachromatic substances in fresh sections of epiphyseal cartilage from rachitic rats. In vitro calcification determined calcifiability. X-irradiation with 250,000 r resulted in a small decrease of calcifiability, loss of [beta]-metachromatic granules from some cells in the proliferative zone, and a slight decrease in staining of the hypertrophic cells. X-irradiation with 500,000 r was followed by a marked decrease in calcifiability, loss of most of the [beta]-metachromatic granules of the proliferative zone, and loss of gamma-metachromatic granules from some of the hypertrophic cells. X-irradiation with 1,000,000 r resulted in almost complete loss of both calcifiability and stainability with toluidine blue. The effect of irradiation was considerably reduced if it was applied shortly after the process of calcification had commenced. It was suggested that a change''in mucopolysaccharide resulting in an increase of free electronegative groups may be associated with calcifiability of epiphyseal cartilage.