Effects of Methyl paraben neonatal treatment on puberty onset, estrus cycle, and development of ovarian follicles in female mice (Balb/c)

Methyl paraben (MP) is an xsenoestrogen pollutant that is classified into preservatives due to its antibacterial properties. The aim of the present study was to investigate the effects of MP in female neonatal mice on puberty timing, estrus cycle, and ovarian follicle profile.

In this experimental study, one-day-old Balb/c mice were randomly divided into 5 groups (n = 8), including the control, vehicle, and three groups with doses of 0.8, 4 and 20 mg/kg of methyl paraben, respectively. Subcutaneous injection was performed in the first 5 days after birth and once a day. The day of vaginal opening was considered as a sign of puberty and estrus cycle for one month. Then, the mice were sacrificed in 70 days; their serumand ovary were collected for studies of hormonal measurement and counting of follicles.Statistical analysis was performed using SPSS Inc., Chicago, IL; Version 18 and one-way analysis of variance was used for comparingthe groups.

The day of puberty onset advanced by 4 (p<0.05) and 20MP (p<0.001). Duration mean of estrus cycle in 4 (p<0.05) and 20MP (p<0.001) and diestrus index in 4 (p<0.01) and 20MP (p<0.001) increased compared to the control group. Reduction in the number of ovarian follicles and corpus luteum was observed in 4 and MP20 groups. The concentration of estradiol increased in 4 (p <0.05) and MP20 (p <0.001) groups and the concentration of LH in 4 and MP20 groups was decreased compared to the control group (p <0.001).

The study showed that exposure to the MP the during neonatal period could lead to Precocious puberty, estrus dysfunction, decreased ovarian follicle content and corpus luteum and impaired secretion of sex hormones.