The effect of x-irradiation on the lysosomes of mouse mammary gland carcinomas.

The distribution of acid phosphatase in mouse mammary tumors was studied by light and electron microscopy technics. Following X-irradiation, the concentration and size of the lysosomes in the tumor cells were increased, and final reaction products of the histochemical test were detected free in the cytoplasm and in intercellular spaces. Areas of focal degradation and necrobiosis appeared associated with enlarged lysosomes, and were more frequently detected in the irradiated tumors from mice treated with vitamin A. Ionizing radiation appeared to provoke the release and activa tion of lysosomal hydrolases and these seemed to be associated with the degradative changes in the tumor cells. Lysosomes, characterized by their acid phosphatase activity, were detected in the irradiated tumor cells prior to the onset of easily detectable cytoplasmic changes by routine histologie preparations. The use of the acid phosphatase test may represent a convenient method for detecting early cytologie changes following irradia tion.