Fertility decline induced by subchronic exposure to an atrazine–mesotrione mixture in male Wistar rats

A commercial atrazine-mesotrione mixture (Calaris®) is widely used in agriculture due to its improved weed control. However, toxicological data on this combination remain elusive, especially regarding its effects on mammalian health. Herein, we investigated the effects of subchronic exposure to 2 and 20 mg Kg -1 of Calaris® in male Wistar rats, focusing on reproductive parameters. Eighty days of daily exposure to 20 mg Kg -1 of Calaris® elicited nitrosative stress and ionic disturbance in the hypothalamus, and low serum LH levels. In the testis, the highest dose disrupted the activity of antioxidant enzymes, total and Mg 2+ -ATPases, interfered with the homeostasis of Fe, Zn, Mg, and Se, and damaged the DNA of testicular cells. Although the number of normal seminiferous tubules was higher than that of abnormal tubules, alterations in epithelium height and luminal diameter reflected the low number of spermatids and daily sperm production. Spermatozoa were exposed to an oxidative and nitrosative environment in the proximal epididymis and a nitrosative stress in its distal portion. Rats exposed to the highest dose exhibited low sperm motility and midpiece mitochondria activity, besides a high rate of preimplantation loss after mating with healthy females. Their fetuses, in turn, showed a low anogenital distance, suggesting possible epigenetic and/or endocrine effects. Calaris® at low dose caused less damage than the highest dose, primarily affecting the nitrosative and ionic balance of the tissues. Our findings raise concerns about the long-term safety of pesticide mixtures, underscoring the need to understand environmental risk assessments for combined agrochemical exposures. • Calaris® reduces male rat fertility; increases pre-implantation losses. • Atrazine/mesotrione mixture causes oxidative stress in hypothalamic-gonadal axis. • Calaris® impairs hormones (LH, testosterone) in hypothalamic-gonadal axis. • Testicular DNA damage reduces sperm production and quality. • Atrazine/mesotrione exposure impairs sperm mitochondrial activity.