Background: Thiamethoxam (TMX) is a widespread neonicotinoid insecticide; it thought to have a toxic effect on uterine and ovarian tissue. This experiment aimed to evaluate the possible antioxidant protective role of both the pycnogenol and L-arginine against this damage using histological, immunohistochemical, and morphometric analysis.

Methods: Forty eight female albino rats were randomly divided into 4 groups; twelve rats per group as follows: 312 mg/kg thiomethoxame group (Tx group), 40 mg/kg pycnogenol + 312 mg/kg thiomethoxame group (Tx /Pg group), 1.3 g/kg L-arginine +312 mg/kg thiomethoxame group ((Tx /La group), and a healthy control group. The rats were supplied with L-arginine, Pycnogenol, TMX, and distilled water once a day for 30 days then sacrificed. Ovarian and uterine tissues were removed for biochemical and histological analysis.

Result: A decrease in the activities of glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) and increasing malondialdehyde (MDA) levels in Tx group, TMX caused a marked oxidative stress. Also, tissue damage in the same group appeared in the form of atretic and vacuolated ovarian follicles with degenerated uterine gland. Immunohistochemistry data, showed elevated level of cytoplasmic reactivity to caspase3 with decrease reaction to Nfr2 in Tx group as compared to other groups. Pycnogenol and L-arginine administration revealed significant restoration of normal histological and immunohistochemical tissue form.

Conclusion: The present findings suggest that Pycnogenol and L-arginine could improve the ovarian and uterine damage resulting from administration of thiomethoxame.