Perinatal exposure to environmentally relevant levels of bisphenol A decreases fertility and fecundity in CD-1 mice

Abstract

Background: Perinatal exposure to low-doses of bisphenol A (BPA) results in alterations in the ovary, uterus, and mammary glands and in a sexually dimorphic region of the brain known to be important for estrous cyclicity.

Objectives: We aimed to determine whether perinatal exposure to environmentally relevant doses of BPA alters reproductive capacity.

Methods: Female CD-1 mice that were exposed to BPA at 0, 25 ng, 250 ng, or 25 µg/kg body weight (BW)/day or diethylstilbestrol (DES) at 10 ng/kg BW/day (positive control) from gestational day 8 through day 16 of lactation were continuously housed with proven breeder males for 32 weeks starting at 2 months of age. At each delivery, pups born to these mating pairs were removed. The cumulative number of pups, number of deliveries, and litter size were recorded. The purity of the BPA used in this and our previous studies was assessed using HPLC, mass spectrometry, and nuclear magnetic resonance.

Results: The forced breeding experiment revealed a decrease in the cumulative number of pups, observed as a nonmonotonic dose-response effect, and a decline in fertility and fecundity over time in female mice exposed perinatally to BPA. The BPA was 97% pure, with no evidence of contamination by other phenolic compounds.

Conclusions: Perinatal exposure to BPA leads to a dose-dependent decline in the reproductive capacity of female mice. The effects on the cumulative number of pups are comparable to those previously reported in mice developmentally exposed to DES, a compound well known to impair reproduction in women. This association suggests the possibility that early BPA exposure may also affect reproductive capacity in women.

Figure 1

Diode area detector HPLC-UV analysis (A) and 600 MHz ¹H NMR spectrum (B) of the BPA used in these experiments (Sigma Aldrich catalog no. 23965-8).

Figure 2

Reproductive capacity of mice exposed perinatally to BPA or 10 ng/kg BW/day DES, expressed as the cumulative number of pups born per dam over a period of 32 weeks of forced breeding (mean ± SE). n, number of dams at the beginning of each experiment. Statistical analysis was performed using the Kolmogorov–Smirnov test. For BPA 25 ng/kg and BPA 25 μg/kg compared with controls during the same week, *p < 0.05 for weeks 16–24, and **p < 0.01 for weeks 25–32. For DES compared with controls for the same week, ^#p < 0.05 for weeks 25–32.

Figure 3

Results after 32 weeks of forced breeding expressed as (A) the total number of litters per dam (mean ± SE) and (B) percentage of CD-1 female mice per group with greater than or fewer than six litters. n, number of dams at the beginning of each experiment. ^#p = 0.024 compared with control, by ANOVA followed by Dunnett’s test. ^##p = 0.012 compared with control, by Fisher’s exact test.

Figure 4

Scatterplot of the number of pups delivered by each dam per litter for control (A; n = 21), BPA 25 ng/kg (B; n = 19), BPA 250 ng/kg (C; n = 18), BPA 25 μg/kg (D; n = 20), and DES 10 ng/kg (E; n = 22) groups. n, number of dams at the beginning of each experiment. Each data point may represent more than one litter because of overlapping data. The slope and the correlation coefficients (R) of the trend lines were significantly different for the BPA 25 μg/kg group compared with both the control and BPA 250 ng/kg groups.