Background: Bisphenol A (BPA) is a widely produced endocrine-disrupting chemical. Diet is a primary route of exposure, but internal exposure (serum concentrations) in animals and humans has been measured only after single oral bolus administration.Objective: We compared serum concentrations of BPA over a 24-hr period after oral bolus administration or ad libitum feeding in mice and assessed for buildup with dietary exposure.Methods: Adult female mice were administered [dimethyl-d6]-BPA (BPA-d6) as a single oral bolus (20 mg/kg body weight) or fed a diet containing 100 mg BPA-d6/kg feed weight ad libitum for 1 week. Serum concentrations were analyzed using isotope dilution liquid chromatography coupled with electrospray tandem mass spectrometry and compared between exposure groups over the first 23 hr and after 7 days of dietary exposure.Results: Maximum concentration (Cmax) for BPA-d6 during the first 24 hr was reached at 1 hr and 6 hr for oral bolus and diet groups, respectively. Relative BPA-d6 bioavailability (unconjugated BPA-d6) was higher in diet-exposed mice than in the bolus group despite a relative lower absorption, a phenomenon consistent with an inhibitory effect of food on first-pass hepatic metabolism. In mice with ongoing dietary exposure, unconjugated BPA-d6 was higher on day 7 than on day 1.Conclusions: This is the first report of serum BPA concentrations in an animal model exposed to this chemical via the diet. Although bolus administration of BPA-d6 led to peak concentrations within 1 hr, Cmax for diet-exposed mice was delayed for several hours. However, bolus administration underestimates bioavailable serum BPA concentrations in animals—and presumably humans—than would result from dietary exposure. Exposure via diet is a more natural continuous exposure route than oral bolus exposure and is thus a better predictor of BPA concentrations in chronically exposed animals and humans.

Bisphenol A (BPA), a pervasive, endocrine disrupting compound (EDC), acts as a mixed agonist- antagonist with respect to estrogens and other steroid hormones. We hypothesized that sexually selected traits would be particularly sensitive to EDC. Consistent with this concept, developmental exposure of males from the polygynous deer mouse, Peromyscus maniculatus, to BPA resulted in compromised spatial navigational ability and exploratory behaviors, while there was little effect on females. Here, we have examined a related, monogamous species, the California mouse (Peromyscus californicus), where we predicted that males would be less sensitive to BPA in terms of navigational and exploratory behaviors, while displaying other traits related to interactions with females and territorial marking that might be vulnerable to disruption. As in the deer mouse experiments, females were fed either a phytoestrogen-free CTL diet through pregnancy and lactation or the same diet supplemented with BPA (50 mg/kg feed weight) or ethinyl estradiol (EE) (0.1 part per billion) to provide a “pure” estrogen control. After weaning, pups were maintained on CTL diet until they had reached sexual maturity, at which time behaviors were evaluated. In addition, territorial marking was assessed in BPA-exposed males housed alone and when a control male was visible in the testing arena. In contrast to deer mice, BPA and EE exposure had no effect on spatial navigational skills in either male or female California mice. While CTL females exhibited greater exploratory behavior than CTL males, BPA exposure abolished this sex difference. BPA-exposed males, however, engaged in less territorial marking when CTL males were present. These studies demonstrate that developmental BPA exposure can disrupt adult behaviors in a sex- and species-dependent manner and are consistent with the hypothesis that sexually selected traits are particularly vulnerable to endocrine disruption and should be a consideration in risk assessment studies.

Reports that maternal diet influences coat color in mouse offspring carrying the agouti A vy allele have received considerable attention because the range, from pseudoagouti (brown) to yellow, predicts adult health outcomes, especially disposition toward obesity and diabetes, in yellower mice. Bisphenol A (BPA), an endocrine-disrupting compound with estrogenic properties, fed to a/a dams harboring A vy /a conceptuses has been reported to induce a significant shift toward yellower mice, whereas consumption of either genistein (G) alone or in combination with BPA led to greater numbers of healthy, brown offspring. Groups of C57/B6 a/a females, which are nonagouti, were fed either a phytoestrogen-free control diet or one of six experimental diets: diets 1-3 contained BPA (50 mg, 5 mg, and 50 μg BPA/kg food, respectively); diet 4 contained G (250 mg/kg food); diet 5 contained G plus BPA (250 and 50 mg/kg food, respectively); and diet 6 contained 0.1 μg of ethinyl estradiol (EE)/kg food. Mice were bred to A vy /a males over multiple parities. In all, 2,824 pups from 426 litters were born. None of the diets provided any significant differences in relative numbers of brown, yellow, or intermediate coat color A vy /a offspring. However, BPA plus G (P < 0.0001) and EE diets (P = 0.005), but not the four others, decreased the percentage of black (a/a) to A vy /a offspring from the expected Mendelian ratio of 1:1. Data suggest that A vy /a conceptuses, which may possess a so-called "thrifty genotype," are at a competitive advantage over a/a conceptuses in certain uterine environments.endocrine disruption | pregnancy | viable yellow mouse | epigenetics | metabolic disease

Mice carrying the Avy allele are epigenetic mosaics. If the majority of cells have an active (demethylated) intracisternal A particle (IAP), mice have a yellow coat color and develop adult-onset obesity and diabetes, while mice whose mosaicism predominantly reflects an inactive (methylated) IAP are pseudoagouti (brown) and less prone to metabolic disease. Brown and yellow coat color Avy/a post-weaning mice were placed on one of three diets (AIN, and two lower calorie diets NIH and methyl-supplemented, NIHMe) to determine whether coat color, weight gain, blood glucose, and methylation of hepatic IAP became altered. None of the diets altered Avy/a mice coat color. NIHMe did not protect against increasing obesity or the usual onset of hyperglycemia in males. Nor did it promote increased methylation of Avy IAP in liver tissue. By contrast, AIN, despite its higher content of fat and carbohydrate and ability to promote greater weight gains than the NIH and NIHMe diets, protected males better against hyperglycemia than either the NIH or NIHMe diets. This diet led to a significantly reduced (~ 50 %; P = 0.003) average methylation state of all CpG sites within the hepatic IAP for the pseudoagouti mice. On AIN, but not on the other diets, extent of hepatic IAP methylation was negatively correlated (R = 0.97, P ≤ 0.001) with body weight of pseudoagouti mice. The findings indicate that post-weaning diet might influence interpretation of studies with Avy/a mice because IAP methylation patterns may be malleable in certain organs and influenced by post-weaning diet.