Temporal effect of methyl parathion on ovarian compensatory hypertrophy, follicular dynamics and estrous cycle in hemicastrated albino rats.

Methyl parathion, an organophosphorus pesticide, was administered i.p. at a dose of 5 mg/kg body weight to hemicastrated virgin rats for 1, 5, 10 and 15 days. Treatment with methyl parathion for 1 and 5 days revealed no change in the ovarian weight with -0.64% and -9.63% hypertrophy respectively and no change in healthy and atretic follicles when compared with hemicastrated oil-treated controls. However, treatment with methyl parathion for 10 and 15 days resulted in a significant decrease in ovarian weight gain with -21.36% and -31.98% hypertrophy, respectively, a significant decrease in the number of healthy follicles, and no change in the number of atretic follicles. The number of estrous cycles and duration of each phase of the estrous cycle were significantly affected with methyl parathion treatment for 5, 10 and 15 days. However, there were no significant changes in the number of estrous cycles and duration of estrus and metestrus phases in 1 day methyl parathion treatment except for a decrease and increase in proestrus and diestrus phases respectively. The weight of the uterus was significantly decreased whereas those of the liver, kidney and adrenal did not change in any of the methyl parathion treated groups.