Background: The rapid development of nanotechnology has given rise to broad applications of nanoparticles (NPs) in biomedicine. This material is distributed in all parts of the body, rapidly after injection, by circulation and reach to all organs and tissues. Before their application as medicine, toxic effects of them on human and animals should be assessed. In this study, the effects of zinc oxide nanoparticle on histopathological changes of epididymis in adult male mice was investigated.

Materials and methods: In this experimental study, 30 adult male NMRI mice were used. The animals were assigned as control, sham and three experimental groups (n=6). Sham and experimental groups received 1ml of distilled water and experimental animals received different doses of nano zinc oxide (250, 500 and 700 mg/kg, i.p. injection, respectively). Treatments was performed for one day. After a week, effects of zinc oxide nanoparticle on histopathological changes of epididym tissue were studied. Data were analyzed by ANOVA and Tukey test.

Results: Administration of zinc oxide nanoparticle in 250 mg/kg dose caused significant reduction in the number of sperm cells. Also, zinc oxide nanoparticle in 250 mg/kg dose lead to degenerated epididymis cells in epididymis tubules. There were no significant changes in diameter of epididymis tubules and number of epididymis tubules.

Conclusion: According to the results of this study, zinc oxide nanoparticles may cause adverse effects on the reproductive system. So, we recommend to avoid using products containing nanoparticles of zinc oxide.

Keywords: Zinc oxide nanoparticles, Epididymis tissue, Sperm cells, Mice.