Developmental exposure to endocrine-disrupting compounds may adversely affect female reproductive physiology. The present study investigated the effect of Pirimiphos-methyl (PM), an organophosphate pesticide, widely used to protect crops and grains against pests, on puberty onset in female rats. Female weanling rats were orally treated with 20 mg/kg and 40 mg/kg of PM for ten consecutive days from postnatal day 22 to 31. Following vagina opening and attainment of estrus and dioestrus phases of the estrous cycle, rats were sacrificed by cervical dislocation. Blood was collected via cardiac puncture to determine serum level of progesterone, oestradiol (E2) and anti-mullerian hormone (AMH) using enzyme-linked immunosorbent assay. Ovaries were collected to determine follicular count as well as the expression of gonadotropin-releasing hormone (GnRH) receptor by immunohistochemistry. Exposure to 20 mg/kg of PM for 10 days advanced vaginal opening. Ovaries were undersized and showed decreased number of follicles in PM-treated rats. Serum levels of progesterone and AMH were reduced (P<0.05) by PM treatment while E2 level was increased (P<0.05) when compared with control. The expression of ovarian GnRH receptor was significantly reduced following exposure to 20 mg/kg of PM. In conclusion, the present study showed that PM-induced puberty advancement is related to disturbance in the activity of the hypothalamicpituitarygonadal axis.
Keywords: pirimiphos-methyl, puberty, anti mullerian hormone, estrous, immunohistochemistry.