To assess the cytotoxicity of Shiga toxin 2, filtrated culture supernatants of E. coli O139 (pig isolate, 100 CD50/ml) were loaded to primary porcine arterial endothelial (PAE) cells and Vero cells. These cells were morphologically examined after 24 hours of exposure. Clotted or fragmented nuclear chromatin and convoluted or protuberated cytoplasm were observed both in the PAE cells and Vero cells by light microscopy. DNA fragmentation was detected in these cells by the transferase-mediated dUTP-biotin nick end labeling (TUNEL) method. Moreover, the characteristics of apoptosis, segregation of condensed chromatin attaching to the convoluted nuclear outline or formation of apoptotic bodies, were confirmed ultrastructurally. These results show the association of apoptosis in the cytotoxicity of Shiga toxin 2. (Toxico-Pathology Section, Department of Safety Research TEL+81-298+38+7818)
