Effect of Dimethoate Administration Schedules on Compensatory Ovarian Hypertrophy, Follicular Dynamics, and Estrous Cycle in Hemicastrated Mice

Abstract

Dimethoate, a widely used organophosphate insecticide, was administered orally (28 mg/kg body weight) to hemicastrated (HC) virgin mice on day 1 and for 5, 10, and 15 days. Hemicastrated untreated control mice showed a significant increase in relative ovarian weight, with 42.74% hypertrophy and an increase in healthy and atretic follicles when compared with those of sham-operated control animals. The HC mice treated for 1 day or for 5 days showed no significant change in ovarian weight (36.64% and 25.19% hypertrophy, respectively) or in healthy and atretic follicles, when compared with HC-control mice. Treatment with dimethoate for 10 or 15 days, however, resulted in a significant decrease in ovarian weight (19.84% and 0.76% hypertrophy, respectively), a significant decrease in the number of healthy follicles, and a concomitant significant increase in the number of atretic follicles when compared with those in HC control animals. No significant change occurred in the number of estrous cycles or duration of each phase of the estrous cycle in HC mice treated with dimethoate for either 1 or 5 days. In HC mice treated with dimethoate for 10 or 15 days, however, a significant decrease in the number of estrous cycles, duration of proestrus, estrus, and metestrus, a concomitant significant increase in the diestrus phase, when compared with HC control animals. In mice receiving dimethoate for 15 days (but not for 1, 5, or 10 days) a significant decrease occurred in body weight and in the weights of the uterus, kidney, spleen, and liver when compared with the parallel weights in HC control animals. The overall findings suggest that following dimethoate treatment, a significant decrease in ovarian weight with a concomitant increase in compensatory ovarian hypertrophy and in the number of healthy follicles, with a concomitant increase in the number of atretic follicles and interrupted estrous cycles, may be due to the direct effect on the ovary or may be due to a hormonal imbalance in any stage of the hypothalamo-hypophysial ovarian axis.

Organophosphate and Pyrethroid Pesticide Exposures Measured before Conception and Associations with Time to Pregnancy in Chinese Couples Enrolled in the Shanghai Birth Cohort

“…2013 ). Another possible mechanism might be through effects on follicular development ( Ghodageri and Katti 2013 ; Mahadevaswami and Kaliwal 2002 ; Nair et al. 2014 ; Katti et al.…”

Effects of Trichlorfon on Maternal Estrous Cycle, Oocyte Maturation, and Near-term Fetal Developmental Outcome in Mice

“…Cyclic changes in the vaginal smear indicate ovarian activity, which is controlled by the hypothalamopituitary unit; the phases vaginal cells go through represent parallel changes in the entire reproductive tract and, hence, are diagnostic 25) . Some toxicity studies of OP pesticides, such as methyl parathion 26) , monocrotophos 27) , and dimethoate 28) , on animal estrous cycles have reported inconsistent results. In our study, control mice exhibited regular estrous cycle of 4-5 d. Mice treated with TCF exhibited no significant changes in the mean estrous cycle and duration of each phases.…”

Developmental toxicity of orally administered technical dimethoate in rats

“…Not only does it increase the frequency of chromosomal aberrations and sister chromatid exchanges in peripheral lymphocytes from male pesticides applicators (Rupa et al, 1991), but dimethoate accelerated bone resorption activity in young rats during the suckling period after mothers exposure to 40 mg/kg/day from days 0-10 after delivery (Amira et al, 2005). Dimethoate and has a direct effect on the ovaries in the mice exposed to 28 mg/kg/ day for 5, 10, and 15 days (Mahadevaswami and Kaliwal, 2002). Furthermore, it decreased serum testosterone levels, testicular weight, and sperm motility, and increased the percentage of dead and abnormal sperm in male rats exposed orally to two dosage levels of 6.25 and 12.5 for 65 consecutive days (Afifi et al, 1991).…”