ABSTRACT
Administration of 5 mg methomyl (40%) kg-1 b.wt. mouse-1 (equal to 50% of LD50 dose), every day for 90 days to adult female mice resulted in a significant decrease in body weight, relative weight of the ovary, uterus and fallopian tube; mean number of small, preantral, antral and pre-ovulatory follicles and fertility compared to controls. On the other hand, total duration of the estrous cycle was significantly increased compared to controls. One month after the cessation of the treatment (a commercial methomyl preparation-lannate) the effect on estrous cycle and organ weight was not restored. Treatment of 2.5 mg or 1 mg lannate kg-1 b. wt., although did not alter duration of the estrous cycle; relative weight of the ovary, uterus, and fallopian tube and fertility, caused a significant decrease in mean number of small follicles compared to controls. All the groups of mice treated with lannate showed loss in body weight (15.15% in 1 mg, 6.61% in 2 mg and 12.16% in 5 mg treated groups) whereas controls showed a gain in body weight (20.02%) during the period of experimentation. The results indicate that 5 mg lannate kg-1 b. wt. causes loss of follicles and infertility, whereas lower dosages (2.5 and 1 mg) reduce the number of small follicles which might shorten reproductive life span of mice.