DNA damage in organs of female and male mice exposed to nonylphenol, as a single agent or in combination with ionizing irradiation: A comet assay study

• Genotoxicity of nonylphenol (NP) and irradiation-NP combination in somatic cells of mice were assessed.
• Impact of NP on the induction of DNA damage differs depending on tissue and sex.
• The genetic material of female mice somatic cells is less sensitive to damage DNA induced by NP.
• In females NP-irradiation co-administration may enhance the level of DNA damage in some organs.
• Genetic material of male's cells showed diminished damage after combined irradiation-NP exposure.

The effect of nonylphenol (NP; either alone or in combination with ionizing radiation) on the induction of DNA strand breaks in mouse somatic cells has been examined. Male and female mice were repeatedly irradiated with X-rays (0.05 or 0.10 Gy), injected with NP (25 or 50 mg/kg bw), or both (0.05 Gy + 25 mg/kg bw NP or 0.10 Gy + 50 mg/kg bw NP), for 2 weeks, 5 days/week. Liver, spleen, femora, lungs and kidneys were removed from each animal for the comet assay. NP-induced DNA damage differed, depending on organ and sex. In male mice, NP induced damage in all organs examined; in females, only the kidneys were affected. The effect of irradiation alone was similar in females and males. Combined exposure of males to 0.05 Gy + 25 mg/kg bw NP significantly reduced the level of DNA strand breaks, compared to the controls and to 25 mg/kg bw NP alone, in the majority of organs. The higher doses significantly increased damage to DNA in all organs examined. Combined exposure of females to low doses of both agents significantly enhanced damage to DNA in bone marrow lymphocytes and in cells of the liver and kidneys, compared to controls. At 0.10 Gy + 50 mg/kg bw NP, DNA damage was increased in organs except liver and spleen. Although NP alone may not be mutagenic in female mice, its co-administration with irradiation may increase DNA damage in some organs. In contrast, in male mice, damage was reduced after combined irradiation-NP exposure, compared to NP alone.