Effect of irradiation on lysosomal enzyme activation in cultured macrophages

The effect of gamma-rays on lysosomal enzyme activity of normal and immune macrophages of DBA/2 mice cultured in vitro has been studied. Quantitative cytochemical methods have been used for measuring lysosomal enzyme activity. A dose of 500 rad did not significantly affect lysosomal enzyme activity 3 hours after irradiation but caused the activity to increase to 1x4 times the control value 22x5 hours after irradiation. 22x5 hours after a dose of 3000 rad the enzyme activity increased to 2x5 times the control. Lysosomal enzyme activity of the macrophages was also markedly increased by immunization of the mice with D lymphoma cells, before culture in vitro, but irradiation of these cells with a dose of 500 rad caused a further increase in lysosomal enzyme activity. The results indicate that immunization and irradiation both cause stimulation of lysosomal enzyme activity in macrophages but that the mechanisms of activation are unlikely to be identical.