This study aimed to evaluate the adverse effects of the insecticide imidacloprid (IMI) on male spermatogenesis, steroidogenesis, and DNA damage in sexually mature and immature rats. Forty male rats (mature and immature) were equally divided into four groups: two mature and two immature groups. IMI groups of both ages were orally administered IMI in corn oil at a concentration of 1 mg/mL for kg BW/day, whereas their respective controls were orally administered corn oil only (1 mL/kg of body weight) daily for 65 days. On day 66, the rats were lightly anesthetized and then euthanized by cervical dislocation. Whole blood was collected for hemogram, serum for hormonal profile, semen for sperm profile, and testes for gene expression and histopathological, and immunohistochemical examinations. The obtained results revealed that both sexually mature and immature rats orally exposed to IMI showed serious abnormalities in sperm morphology and concentrations, with an imbalance of sexual hormones. There were increases in the level of serum 8-hydroxy-2'-deoxyguanosine and in the percentage of comet (tailed) sperm DNA in the IMI-treated groups. The results exhibited the upregulation of a DNA damage tolerance gene (8-oxoguanine glycosylase 1) and downregulation of the activity of steroidogenic genes (nuclear receptor subfamily 5, group A, member 1 and 3β-hydroxysteroid dehydrogenase). Immunohistochemical examination of the B-cell lymphoma 2-associated X apoptotic protein in testicular sections showed various degrees of apoptosis in the spermatogonial cells of the IMI-treated rats compared to the control groups. These damaging effects of IMI were more pronounced in the sexually mature rats than in the immature rats. In conclusion, despite using a low dose of IMI in the present study, there were noticeable harmful consequences on the reproductive system at different stages of sexual maturity in male rats.
Keywords: 8-OHdG; Bax; Comet; Neonicotinoid; Spermatogenesis.
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