Endonuclease-induced DNA fragmentation is a hallmark of apoptosis. DNase gamma (DNase γ) was recently identified as one of the endonucleases responsible for apoptotic DNA fragmentation. In this study, immunohistochemistry for DNase y was performed on paraffin sections of rodent liver in well-defined models of hepatocyte apoptosis induced by Fas antibody (Fas) or cycloheximide (CHX), and necrosis induced by lipopolysaccharide (LPS) or carbon tetrachloride (CCl4). DNase y immunoreactivity was compared with TdT-mediated dUTP nick-end labeling (TUNEL) reactivity. Our results showed TUNEL reactivity in both apoptotic and necrotic hepatocytes. DNase y immunoreactivity was not detected during LPS-induced or CCl4-induced hepatocyte necrosis. In contrast, it was evident during CHX-induced, but not Fas-induced, apoptotic DNA fragmentation. These findings suggest that DNase y plays an important role in Fasindependent apoptotic DNA fragmentation in hepatocytes.
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