Metanil yellow impairs the estrous cycle physiology and ovarian folliculogenesis in female rats.

Metanil yellow (MY) is a most frequently used food color in West Bengal, India. The toxic effects of MY on the male reproductive system have been reported discriminately in animal models. The probable toxic effects of MY on female reproductive functions have not been reported till date. Therefore, this study was designed to examine the effect of MY on estrous cycle rhythmicity and ovarian folliculogenesis in female rats. Rats have been exposed to MY at three doses of 250, 500, 750 mg kgBW-1  day-1 for two exposure durations, 20 and 30 days. We observed significant changes in the number and duration of estrous cycle along with prominent cytoarchitectural changes in the cellular characteristics of vaginal smear of component phases of estrous cycle in a dose and duration-dependent manner in MY-treated rats compared to control rats. We also observed a significant decrease in serum follicle stimulating hormone (FSH), luteinizing hormone (LH), and estradiol levels in MY-treated rats. Further, the activities of some antioxidants enzymes in brain tissues of MY-treated rats were significantly decreased and the level of malondialdehyde (MDA), a marker of lipid peroxidation, in brain tissues of MY-treated rats was also significantly increased. The ovarian folliculogenesis in this study was also significantly impaired in MY-treated rats. In conclusion, MY impairs the estrous cycle and ovarian folliculogenesis in female rats by inhibiting the secretion of FSH and estradiol from the ovary, and inducing the oxidative stress in hypothalamic-pituitary-gonadal axis.