Abstract
Ultrastructural changes of splenic macrophages of rats after γ-ray irradiation were investigated, especially focused on lysosomal behaviors together with the cytochemical demonstration of acid phosphatase (AcPase) activity. γ-ray irradiation (total 800 rads) caused extensive phagocytosis in splenic macrophages. Damaged lymphocytes and erythrocytes were massively phagocytosed by these macrophages. The large number of heterophagosomes thus formed within macrophages subsequently acquired AcPase activity and converted to large heterophagolysosomes (HPL). Then, some portions of large HPL started to show constrictions which resulted in the separation and formation of many small lysosomes. Some of large HPL further became flattened and projected pseudopod-like processes which surrounded some cytoplasmic area or organelles of macrophage, especially small lysosomes, forming autophagolysosomes. These lysosomal behaviors may be related to the regulation or self-control of the lysosomal system within macrophages.
