The purpose of this study was to investigate diethylnitrosamine (DEN)-induced liver damage in zebrafish. Zebrafish larvae were divided into five groups after seventy-two hours fertilization: group 1 (G1) as control, group 2 (G2) as probe control, groups 3, 4, and 5 (G3, G4, and G5) as DEN treated at doses of 25, 50, and 100 μg/mL, respectively. At twenty-two hours after DEN treatment, groups 2, 3, 4, and 5 were treated with ApoFlamma H 675 at a dose of 100 μM/zebrafish. They were examined by fluorescence stereomicroscope at twenty-four hours after DEN treatment. After fixation, the zebrafish were processed, embedded, sectioned and stained with hematoxylin and eosin (HE) and terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL) staining. Fluorescence intensity of the livers of G3, G4, and G5 was significantly increased compared with those of G1 (p<0.01). Furthermore, fluorescence intensity of the livers of G3 and G5 was significantly increased compared with those of G2 (p<0.05 and p<0.01). HE staining showed cell deaths in the livers of DEN-treated zebrafish and TUNEL staining confirmed cell death in the same location. Taken together, in vivo fluorescence bioimaging detected cell death in the liver of DEN-treated zebrafish. This outcome was confirmed with histopathological examination. The results of this study provide confidence for using zebrafish as a liver carcinogenesis model.

Introduction
Materials and Methods
    Animals and treatment
    Fluorescence bioimaging
    Histopathological examination
    Terminal deoxynucleotide transferase dUTP nick endlabeling (TUNEL) staining
    Statistical analysis
Results
    Fluorescence bioimaging
    Histopathological examination
Discussion
References

• Jin Seok Kang(Department of Biomedical Laboratory Science, Namseoul University/Molecular Diagnostics Research Institute, Namseoul University) Corresponding author