γ-H2AX foci as indication for the DNA damage in erythrocytes of medaka (Oryzias latipes) intoxicated with 4-nonylphenol

The present study aimed to investigate the genotoxicity in erythrocytes induced after exposure of medaka (Oryzias latipes) to 4-nonylphenol (4-NP). Adult female medaka fish were exposed to 4-NP at three sublethal concentrations for 15 days to compare their sensitivity with that of catfish as an aquatic model. Comet assay and γ-H2AX were used as biomarkers to detect DNA damage in erythrocytes. Exposure to 4-NP resulted in an increase in the tail moment in a dose-dependent manner. The highest level of DNA damage was recorded after exposure to 100 μg/l 4-NP. The number of foci was increased after exposure to 4-NP, indicating damage to DNA. The present results confirmed the high level of morphological alterations and apoptosis of erythrocytes detected in the first part of this study. 4-NP induced genotoxic effects in medaka, which were found to be more sensitive than catfish after exposure to 4-nonylphenol.