Inhibition of ovarian compensatory hypertrophy by the administration of methyl parathion in hemicastrated albino rats.

Methyl parathion, an organophosphorus pesticide that is a potent acetylcholinesterase inhibitor in animals, was administered IP in graded doses from 2.5 to 5.0 mg/kg body weight to normal hemicastrated virgin rats for 15 consecutive days. Sham-operated and hemicastrated control groups were treated with a similar quantity of olive oil vehicle. The vaginal smears and body weights of treated and control groups were recorded daily and rats were sacrificed on the 16th day. The ovaries, adrenals, liver, kidney, and uterus were removed and weighed, and the ovary from each animal was serially sectioned and stained for histologic studies. The hemicastrated control group revealed a significant increase in ovarian weight with 45% hypertrophy and a significant increase of total healthy and atretic follicles when compared with sham-operated control rats. Treatment with 2.5 and 3.5 mg methyl parathion revealed no change in the ovarian weight with 48 and 42% hypertrophy, respectively, and no change in healthy and atretic follicles when compared with hemicastrated oil-treated controls. However, treatment with 4.0 and 5.0 mg methyl parathion resulted in a significant decrease in ovarian weight gain with 13 and 8% hypertrophy, respectively, a significant decrease in the number of healthy follicles, and no change in the atretic follicles. The number of estrous cycles and duration of each estrous cycle were affected significantly with 3.5, 4.0, and 5.0 mg methyl parathion treatment when compared with controls. There were no significant changes in adrenal, liver, kidney, or uterine weight in the methyl parathion-treated groups except a decrease in uterine weight with 5.0 mg treatment when compared with oil-treated hemicastrated controls.