Lysosomal membrane permeability and acid phosphatase activity have been studied histochemically in sections of tissues from mice which had been subjected to 50-1000 rads whole-body irradiation. After a whole-body dose of 850 rads, no change in lysosomal membrane permeability or of enzyme activity was observed in liver, kidney, heart, or adrenal, but substantial increases of membrane permeability and acid phosphatase activity were observed in spleen and thymus. A dose of 100 rads caused an increase in the permeability of lysosomal membranes in the spleen and after 300 rads the membranes were fully permeable. Enzyme activity was increased, progressively, by doses up to 850 rads and even greater activation of enzyme was observed in the thymus. One hour after 850 rads, enzyme activity in spleen was significantly greater than controls, and it increased to a maximum 48 hr after irradiation. Full recovery of normal membrane permeability and enzyme activity occurred after lower doses. Increased enzyme activity is not considered to be, primarily, a consequence of increased enzyme synthesis or an artifact caused by changes in cell population. Injections of cortisone, hydrocortisone, or chlorambucil cause extensive lymphocytolysis and increase membrane permeability and enzyme activity. Lymphocytes damaged by irradiation are thus believed to release factors which cause increased permeability of the lysosomal membrane and increased acid phosphatase activity.

This content is only available as a PDF.
You do not currently have access to this content.