Comparative estrogenicity of endogenous, environmental and dietary estrogens in pregnant women II: Total estrogenicity calculations accounting for competitive protein and receptor binding and potency.

Evaluating the biological significance of human-relevant exposures to environmental estrogens involves assessing the individual and total estrogenicity of endogenous and exogenous estrogens found in serum, for example from biomonitoring studies. We developed a method for this assessment by integrating approaches for (i) measuring total hormone concentrations by mass spectrometry (Fleck et al., 2018), (ii) calculating hormone bioavailable concentrations in serum and, (iii) solving multiple equilibria between estrogenic ligands and receptors, and (iv) quantitatively describing key elements of estrogen potency. The approach was applied to endogenous (E1, E2, E3, E4), environmental (BPA), and dietary Genistein (GEN), Daidzein (DDZ) estrogens measured in the serum of thirty pregnant women. Fractional receptor occupancy (FRO) based estrogenicity was dominated by E1, E2 and E3 (ER-α, 94.4-99.2% (median: 97.3%), ER-ß, 82.7-97.7% (median: 92.8%), as was the total response (TR), which included ligand specific differences in recruitment of co-activator proteins (RCA). The median FRO for BPA was at least five orders of magnitude lower than E1, E2 and E3, and three orders of magnitude lower than the fetal derived E4 and GEN and DDZ. BPA contributed less than 1/1000th of the normal daily variability in total serum estrogenicity in this cohort of pregnant women.

Placental BCRP/ABCG2 Transporter Prevents Fetal Exposure to the Estrogenic Mycotoxin Zearalenone.

In the placenta, the breast cancer resistance protein (BCRP)/ABCG2 efflux transporter limits the maternal-to-fetal transfer of drugs and chemicals. Previous research has pointed to the estrogenic mycotoxin zearalenone as a potential substrate for BCRP. Here, we sought to assess the role of the BCRP transporter in the transplacental disposition of zearalenone during pregnancy. In vitro transwell transport assays employing BCRP/Bcrp-transfected Madine-Darby canine kidney cells and BeWo trophoblasts with reduced BCRP expression were used to characterize the impact of BCRP on the bidirectional transport of zearalenone. In both models, the presence of BCRP protein increased the basolateral-to-apical transport and reduced the apical-to-basolateral transport of zearalenone over a 2-h period. In vivo pharmacokinetic analyses were then performed using pregnant wild-type and Bcrp-/- mice after a single tail vein injection of zearalenone. Zearalenone and its metabolite α-zearalenol were detectable in serum, placentas, and fetuses from all animals, and ß-zearalenol was detected in serum and fetuses, but not placentas. There were no significant differences in the maternal serum concentrations of any analytes between the two genotypes. In Bcrp-/- mice, the free fetal concentrations of zearalenone, α-zearalenol, and ß-zearalenol were increased by 115%, 84%, and 150%, respectively, when compared with wild-type mice. Concentrations of free zearalenone and α-zearalenol were elevated 145% and 78% in Bcrp-/- placentas, respectively, when compared with wild-type placentas. Taken together, these data indicate that the placental BCRP transporter functions to reduce the fetal accumulation of zearalenone, which may impact susceptibility to developmental toxicities associated with in utero zearalenone exposure.

Interactions between plant-derived oestrogenic substances and the mycoestrogen zearalenone in a bioassay with MCF-7 cells.

Human and animal diets may contain several non-steroidal oestrogenic compounds which originate either from plants (phytoestrogens) or from fungi that infect plants (mycoestrogens such as zearalenone (ZEN)). Phytoestrogens may compete with ZEN in binding to the oestrogen receptor ß and thereby may counteract the oestrogenic activity of ZEN. Using a modified version of the E-screen assay, plant-derived oestrogenic substances were tested for their proliferative or anti-proliferative effect on oestrogen-dependent MCF-7 cells. The samples were additionally tested for their ability to influence the oestrogenic activity of ZEN (1 µM). Among the individual substances tested, 8-prenylnaringenin had the strongest effect, as cell proliferation was increased by 78% at the lowest concentration (0.23 µM), and by 167% at the highest concentration (29.4 µM). Coumestrol (5.83 µM) increased cell proliferation by 39%, and genistein (370 µM) by 61%, respectively. Xanthohumol and enterolactone did not stimulate cell proliferation significantly. In the co-incubation experiments with ZEN, none of the single substances was able to decrease the oestrogenic activity of ZEN. Only for 8-prenylnaringenin (14.7 and 29.4 µM) was a trend towards an increase in the ZEN-induced cell proliferation up to 72% observed. In conclusion, with the exception of 8-prenylnaringenin, no substantial interaction between phytoestrogens and the mycotoxin ZEN could be detected using a bioassays with MCF-7 cells.

[Autism spectrum disorders and bisphenol A: Is serotonin the lacking link in the chain?] / Les relations entre le bisphénol A et les troubles du spectre autistique se précisent : la sérotonine est-elle le lien manquant ?

The etiology of autism spectrum disorders (ASD) is believed to be multifactorial and to involve genetic and environmental components. Environmental chemical exposures are increasingly understood to be important in causing neurotoxicity in fetuses and newborns. Recent data from the Centers for Disease Control and Prevention in the United States suggest a substantial increase in ASD prevalence, only partly explicable by factors such as diagnostic substitution. Bisphenol A (BPA) is an ubiquitous xenoestrogen widely employed in a variety of consumer products including plastic and metal food and beverage containers, dental sealants and fillings, medical equipment and thermal receipts. Therefore, most people are exposed almost continuously to BPA in industrialized countries. Sources of BPA exposure are predominantly diet, but also through inhalation or dermal absorption. BPA can be measured in many human fluids and tissues including saliva, serum, urine, amniotic fluid, follicular fluid, placental tissue and breast milk. There is concern that BPA exposure may influence human brain development and may contribute to the increasing prevalence of neurodevelopmental and behavioural problems. Epigenetic mechanisms are suggested by a mouse study that demonstrated that BPA exposure during gestation had long lasting, transgenerational effects on social recognition. Previous epidemiological studies suggested a relationship between maternal BPA exposure and ASD. A recent study of 46 children with ASD and 52 controls found for the first time a direct association between children with ASD and BPA exposure and demonstrated that BPA is not metabolized well in children with ASD. The metabolomic analyses showed a correlation between ASD and essential amino acid metabolism pathways. Essential amino acids are precursors of neurotransmitters, for example tryptophan for serotonin. Fetal and prenatal BPA exposure was suggested to perturb the serotonergic system in rat and mice models. On the other hand, hyperserotonemia was reported in approximately one-third of autistic patients and also in relatives. Moreover, neuroimaging studies revealed two fundamentally different types of serotonin synthesis abnormality in children with autism compared to age-matched nonautistic children, a difference in whole-brain capacity and focal abnormalities. Finally, decreased serotonin transporter and serotonin receptor binding have been reported in both children and adults with autism. So, the link between BPA and autism could be a defect of the normal in utero or perinatal serotonergic system development. In France, BPA was banned in baby bottles in 2010 and in any food or beverage packaging since January 2015. Therefore, there is an urgent need to find safe alternatives in the use of BPA in the manufacture of industrial products.

Urine and serum biomonitoring of exposure to environmental estrogens I: Bisphenol A in pregnant women.

Despite its very low oral bioavailability and rapid elimination, multiple reports of unexpectedly high bisphenol A (BPA) concentrations in the serum of pregnant mothers or cord blood have raised questions about BPA exposures during pregnancy. Thirty healthy pregnant women recruited to the study were evaluated for total BPA exposure over a 30-h period comprising one-half day in the field and one day in a clinical setting. BPA and its metabolites were measured in serum and total BPA was measured in matching urine samples. The mean total exposure was similar to the 50(th) percentile of exposure for U.S. women and pregnant women in a large North American cohort. Twenty volunteers had total daily exposures equal to or exceeding the U.S. mean, and six volunteers had exposures exceeding the 75th percentile. Women working as cashiers did not have higher total BPA exposure. BPA was detected in some serum samples (0.25-0.51 ng/ml), but showed no relationship to total BPA in corresponding urine samples, no relationship to total BPA exposure, and had unconjugated BPA fractions of 60-80%, consistent with established criteria for sample contamination. We conclude that typical exposures of North American pregnant women produce internal exposures to BPA in the picomolar range.

Pharmacokinetics and safety profiles of novel diethylstilbestrol orally dissolving film in comparison with diethylstilbestrol capsules in healthy Chinese male subjects.

OBJECTIVE: We compared the pharmacokinetic (PK) profiles of diethylstilbestrol orally dissolving film (DES ODF) and DES-capsule as well as assessing the safety, local tolerability, taste, and disintegration time of DES ODF. MATERIALS AND METHODS: Twelve healthy male volunteers receiving a single administration of 2.0 mg of DES ODF or DES-capsule were included in the study. The tolerability, taste, and time to dissolution of DES ODF were assessed after dosing. Safety assessments included adverse events, hematology and biochemistry tests, urinalysis, vital signs, and electrocardiography. RESULTS: The PK parameters of DES ODF were all greater than those of DEScapsule. The Cmax values were 5.64 ± 1.1 and 3.4 ± 1.93 ng/mL for DES ODF and DES-capsule, respectively. Assessment of bioequivalence was based on the 90% CIs of the treatment ratios of the log-transformed Cmax, AUC0-t, and AUC0-∞ (DES ODF to DES-capsule), with the mean values being 1.93 (141 - 264), 1.24 (98 - 156), and 1.59 (121 - 207), respectively, indicating that DES ODF had a significantly high bioavailability. The mean DES ODF disintegration time was 14 ± 5 minutes. DES ODF was well tolerated and no serious adverse events or clinically relevant changes were observed. CONCLUSIONS: The DES ODF is well tolerated and better absorbed in comparison with DES-capsule.

Bisphenol A (BPA) pharmacokinetics with daily oral bolus or continuous exposure via silastic capsules in pregnant rhesus monkeys: Relevance for human exposures.

We measured serum dBPA in non-pregnant and pregnant female rhesus monkeys, fetuses and amniotic fluid. dBPA was administered by a daily oral bolus or sc implantation of Silastic capsules; both resulted in daily average serum unconjugated dBPA concentrations of <1ng/ml. We observed lower serum concentrations of unconjugated dBPA in pregnant females relative to pre-pregnancy values, and generally lower concentrations in fetal serum than in maternal serum. Differences in pharmacokinetics of dBPA were evident between pre-pregnancy, early and late pregnancy, likely reflecting changes in maternal, fetal and placental physiology. The serum ratio of conjugated to unconjugated dBPA after continuous sc release of dBPA was similar to values reported in human biomonitoring studies and markedly lower than with oral administration, suggesting oral bolus exposure is not an appropriate human exposure model. We report elsewhere that there were numerous adverse effects on fetuses exposed to very low serum dBPA in these studies.

Reproductive toxicities of methoxychlor based on estrogenic properties of the compound and its estrogenic metabolite, hydroxyphenyltrichloroethane.

Methoxychlor is an organochlorine pesticide having a weak estrogenicity, which is estimated to be approximately 1000- to 14,000-fold less potent to a natural ligand, 17ß-estradiol. However, its active metabolite, hydroxyphenyltrichloroethane, has much more potent estrogenic activity and probably acts in the target organs of animals exposed to methoxychlor at least 100 times stronger than the parent compound. A variety of in vivo reproductive toxicity studies have shown that treatment with methoxychlor exerts typical endocrine-disrupting effects manifest as estrogenic effects, such as formation of cystic ovaries resulting in ovulation failures, uterine hypertrophy, hormonal imbalances, atrophy of male sexual organs, and deteriorations of sperm production in rats and/or mice, through which it causes serious reproductive damages in both sexes of animals at sufficient dose levels. However, methoxychlor is not teratogenic. The no-observed-adverse-effect level of methoxychlor among reliable experimental animal studies in terms of the reproductive toxicity is 10 ppm (equivalent to 0.600 mg/kg/day) in a two-generation reproduction toxicity study.

Effect of bisphenol A on rat metabolic profiling studied by using capillary electrophoresis time-of-flight mass spectrometry.

Bisphenol A (BPA), a chemical widely used in the manufacture of polycarbonate plastics, has raised considerable concern in recent decades because of its hormone-like properties. Whether BPA exposure is a health risk remains controversial in many countries. A metabolomics study based on capillary electrophoresis time-of-flight mass spectrometry (CE-TOF/MS) was performed to study the urine metabolic profiles of Sprague-Dawley rats fed with four dose levels of BPA (0, 1, 10, and 100 µg/kg body weight) for 45 days. Multivariate pattern recognition directly reflected the metabolic perturbations caused by BPA. On the basis of univariate analysis, 42 metabolites including amino acids, polyamines, nucleosides, organic acids, carbohydrates, pterins, polyphenols, and sugar phosphates were found as the most significantly differential metabolites. The marked perturbations were related with valine, leucine and isoleucine biosynthesis, D-glutamine and D-glutamate metabolism, etc. Significant alterations of neurotransmitters (glutamate, gamma-aminobutyric acid, and noradrenaline) and neurotransmitter-related metabolites (tyrosine, histamine, valine, and taurine) suggested that the toxic effects of small-dose BPA (below 50 mg/kg/day) may contribute to its interactions with the neuromediating system. Our study demonstrated that metabolomics may offer more specific insights into the molecular changes underlying the physiological effects of BPA.

Bisphenol A disposition in the sheep maternal-placental-fetal unit: mechanisms determining fetal internal exposure.

The widespread human exposure to bisphenol A (BPA), a xenoestrogen interfering with developmental processes, raises the question of the mechanisms determining fetal exposure to BPA. A physiological model was developed in ewes to determine whether the pregnancy-associated physiological changes and the metabolic specificities of the fetal-placental unit can influence BPA toxicokinetics (TK) and fetal exposure to BPA. In a first longitudinal study, BPA was infused (2 mg/[kg·day] i.v. for 1 day) into ewes before breeding, at early and late stages of gestation, and after lambing. In a second study, BPA and BPA-glucuronide (BPA-G) were infused intravenously into pregnant ewes or into fetuses at 4 mo of gestation. BPA and its metabolites were assayed in maternal and fetal plasma and amniotic fluid sampled at steady state and after the end of the infusion. The pregnancy status did not modify the TK parameters of BPA and of BPA-G. Five percent of the BPA dose infused into the pregnant ewe was transferred across the placenta to the fetus. The fetal-placental unit was very efficient in metabolizing BPA into conjugated compounds; those metabolites remained trapped in the fetal-placental compartment, leading to a high fetal exposure to BPA conjugates. Taking into account a body weight adjustment, the ovine fetus in late pregnancy is exposed to a BPA dose similar to that of its mother. In contrast to its mother, the fetus exhibits much higher and sustained exposure to BPA metabolites without evidence of their hydrolysis.

Oral homeostasis disruption by medical plasticizer component bisphenol A in adult male rats.

OBJECTIVES/HYPOTHESIS: Bisphenol A (BPA) is a synthetic estrogen-like chemical mimetic widely used in the manufacture of polycarbonate plastics and epoxy resins found in numerous consumer products including food packaging, medical devices, and dental sealants. Because it is recovered in fluids and it can reach high levels in saliva, this study aimed to evaluate its safety on oral homeostasis by examining its effects on salivary glands, mouth epithelium, water consumption, and salt preference, each parameter being estrogen sensitive. STUDY DESIGN: Randomized controlled trial involving rats. METHODS: A dose-response study was conducted in adult Wistar rats randomized into five groups (n = 12). BPA was administered over 6 weeks via drinking water to obtain daily dose exposures of 0 µg/kg, 5 µg/kg, 50 µg/kg, 5 mg/kg, and 12.5 mg/kg of body weight. To evaluate salt preference, 1% NaCl solution and pure water intakes were measured for 3 days by offering two-bottle choices. The rats were then killed; oral biopsies were done and submandibular glands were removed for histologic and morphometric analysis. RESULTS: According to the dose-response curve, BPA decreased total drinking but increased salt preference, which was inversely proportional to water consumption (Kruskal-Wallis, P < .01). It also causes oral dryness and histologic changes in the acinar structures of the submandibular glands at the lowest doses (Kruskal-Wallis, P < .01). CONCLUSIONS: This study shows that oral exposure to BPA in the rat disrupts thirst and buccal homeostasis and raises questions about the salivary gland secretions.

Fetal liver bisphenol A concentrations and biotransformation gene expression reveal variable exposure and altered capacity for metabolism in humans.

Widespread exposure to the endocrine active compound, bisphenol A (BPA), is well documented in humans. A growing body of literature suggests adverse health outcomes associated with varying ranges of exposure to BPA. In the current study, we measured the internal dose of free BPA and conjugated BPA and evaluated gene expression of biotransformation enzymes specific for BPA metabolism in 50 first- and second-trimester human fetal liver samples. Both free BPA and conjugated BPA concentrations varied widely, with free BPA exhibiting three times higher concentrations than conjugated BPA concentrations. As compared to gender-matched adult liver controls, UDP-glucuronyltransferase, sulfotransferase, and steroid sulfatase genes exhibited reduced expression whereas ß-glucuronidase mRNA expression remained unchanged in the fetal tissues. This study provides evidence that there is considerable exposure to BPA during human pregnancy and that the capacity for BPA metabolism is altered in the human fetal liver.

Pharmacokinetics of bisphenol A in serum and adipose tissue following intravenous administration to adult female CD-1 mice.

Bisphenol A (BPA) is an important industrial chemical used as the monomer for polycarbonate plastic and in epoxy resins for use in food can liners. Worldwide biomonitoring studies consistently find high prevalence of BPA conjugates in urine consistent with pervasive exposure at levels typically below 1 µg/kg bw/day. The current study used LC/MS/MS to measure serum pharmacokinetics of unconjugated (active) and conjugated (inactive) BPA in adult female CD-1 mice following intravenous (IV) injection, which produces higher serum levels by circumventing the processes of absorption from the GI tract and presystemic metabolism that occur after oral administration. Deuterated BPA (100 µg/kg bw) was used to avoid interference by background contamination from trace amounts of native BPA. Additionally, the pharmacokinetics of unconjugated BPA were determined in adipose tissue, a proposed site of action and "depot" for BPA. After IV injection, unconjugated BPA rapidly distributed out of the circulation (t(1/2)=0.2 h) and terminal elimination also proceeded rapidly (t(1/2)=0.8 h). Consistent with the degree of aqueous solubility, lipid/water solubility ratio, and partitioning from blood into adipose tissue in vivo, the levels of unconjugated BPA in mouse adipose tissue rapidly reached a maximal level (0.25 h) that did not exceed the serum maximum at the initial sampling time (0.08 h). Terminal elimination of unconjugated BPA from adipose tissue (t(1/2)=7.0 h) was similar to that for conjugated BPA in serum (t(1/2)=6.6 h) and <0.01% of the administered dose remained in adipose tissue after 24 h. These plasma and tissue kinetics are consistent with rapid equilibria and underscore the non-persistent nature of BPA, particularly when compared with slowly metabolized lipophilic organic pollutants like halogenated dibenzodioxins.

Interaction of zearalenone and soybean isoflavone in diets on the growth performance, organ development and serum parameters in prepubertal gilts.

The aim of the present research was to determine the interactive effect of zearalenone (ZEA) and soybean isoflavone (ISO) on the growth performance, development of organs and serum parameters in prepubertal gilts. Ninety 75-day-old female pigs (Duroc × Landrace × Yorkshire, 26.5 ± 0.60 kg) were randomly allocated to nine diet treatments during the 21-day study. The experiment employed a 3 × 3 factorial design using a non-soybean meal diet with the addition of 0, 0.5 or 2.0 mg/kg ZEA and 0, 300 or 600 mg/kg ISO. The results indicated that simultaneous addition of ZEA and ISO had no significant influence on the growth performance in prepubertal gilts. Zearalenone with 2 mg/kg increased (p < 0.05) the relative weight of the reproductive organs (including uterus and vagina) but had no obvious effects (p > 0.05) on the relative weight of the heart, liver, lung, kidney and spleen. Isoflavone at 600 mg/kg could offset the increased weight of the reproductive organs induced by ZEA. Simultaneous addition of ZEA and ISO to prepubertal gilts increased the level of alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase in the serum (p < 0.05) at day 14 but their levels decreased (p < 0.05) over time. Zearalenone increased the level of malondialdehyde and decreased the concentrations of superoxide dismutase and glutathione peroxidase (p < 0.05) in the serum. The results suggested that ISO added to diets at 600 mg/kg could reduce the increase in the relative weight of reproductive organs and relieve the oxidative stress induced by ZEA added at 2 mg/kg during the growth phase in prepubertal gilts.

Twenty-four hour human urine and serum profiles of bisphenol a during high-dietary exposure.

By virtue of its binding to steroid hormone receptors, bisphenol A (BPA, the unconjugated bioactive monomer) is hypothesized to be estrogenic when present in sufficient quantities in the body, raising concerns that widespread exposure to BPA may impact human health. To better understand the internal exposure of adult humans to BPA and the relationship between the serum and urinary pharmacokinetics of BPA, a clinical exposure study was conducted. Blood and urine samples were collected approximately hourly over a 24-h period from 20 adult volunteers who ingested 100% of one of three specified meals comprising standard grocery store food items for breakfast, lunch, and dinner. The volunteers' average consumption of BPA, estimated from the urinary excretion of total BPA ((TOT)BPA = conjugated BPA + BPA), was 0.27 µg/kg body weight (range, 0.03-0.86), 21% greater than the 95th percentile of aggregate exposure in the adult U.S. population. A serum time course of (TOT)BPA was observable only in individuals with exposures 1.3-3.9 times higher than the 95th percentile of aggregate U.S. exposure. The (TOT)BPA urine concentration T(max) was 2.75 h (range, 0.75-5.75 h) post-meal, lagging the serum concentration T(max) by ∼1 h. Serum (TOT)BPA area under the curve per unit BPA exposure was between 21.5 and 79.0 nM•h•kg/µg BPA. Serum (TOT)BPA concentrations ranged from less than or equal to limit of detection (LOD, 1.3 nM) to 5.7 nM and were, on average, 42 times lower than urine concentrations. During these high dietary exposures, (TOT)BPA concentrations in serum were undetectable in 83% of the 320 samples collected and BPA concentrations were determined to be less than or equal to LOD in all samples.

Novel pathway of metabolic activation of bisphenol A-related compounds for estrogenic activity.

We previously demonstrated that estrogenic activity of bisphenol A (BPA) in the yeast estrogen screening assay was increased severalfold after incubation with rat liver S9 fraction in the presence of a NADPH-generating system. In this study, we investigated whether eight BPA-related compounds are similarly activated metabolically by rat liver S9 fraction. Three of the analogs exhibited an increase of estrogenic activity after incubation with rat liver S9 fraction but not with microsomal or cytosolic fraction alone. The structures of the metabolites formed were examined by liquid chromatography/mass spectrometry. In addition to oxidized metabolites such as catechols, we found novel dimer-type metabolites. Some of the putative metabolites were chemically synthesized to confirm their structures. The structural requirements for formation of the metabolites, some of which showed more potent estrogenic activity than the parent substrates, were examined. We have uncovered a new pathway of metabolic activation of certain phenolic compounds, such as BPA analogs, to estrogenic dimer-type compounds.

Absorption and metabolism of the mycotoxin zearalenone and the growth promotor zeranol in Caco-2 cells in vitro.

SCOPE: Zearalenone (ZEN) and α-zearalanol (α-ZAL, zeranol) were studied in differentiated Caco-2 cells and in the Caco-2 Millicell® system in vitro to simulate their in vivo intestinal absorption and metabolism in humans. METHODS AND RESULTS: In addition to metabolic reduction/oxidation, extensive conjugation with glucuronic acid and sulfate of the parent compounds and their phase I metabolites was observed. The positional isomers of the glucuronides and sulfates were unambiguously identified: Sulfonation occurred specifically at the 14-hydroxyl group, whereas glucuronidation was less specific and, in addition to the preferred 14-hydroxyl group, involved the 16- and 7-hydroxyl groups. Using the Caco-2 Millicell® system, an efficient transfer of the glucuronides and sulfates of ZEN and α-ZAL and their phase I metabolites into both the basolateral and the apical compartment was observed after apical administration. The apparent permeability coefficients (P(app) values) of ZEN, α-ZAL and the ZEN metabolite α-zearalenol were determined, using an initial apical concentration of 20 µM and a permeation time of 1 h. CONCLUSION: According to the P(app) values, the three compounds are expected to be extensively and rapidly absorbed from the intestinal lumen in vivo and reach the portal blood both as aglycones and as glucuronide and sulfate conjugates in humans.

Serum bisphenol A pharmacokinetics and prostate neoplastic responses following oral and subcutaneous exposures in neonatal Sprague-Dawley rats.

The present study examines BPA pharmacokinetics in neonatal rats following s.c. injection or oral delivery of 10 µg BPA/kg BW and compares susceptibility to estrogen-induced prostate intraepithelial neoplasia (PIN) following either exposure route. Serum BPA in PND3 rats was measured using HPLC-MS-MS. Free and total BPA at C(max) were 1.77 and 2.0 ng/ml, respectively following injection and 0.26 and 1.02 ng/ml, respectively following oral exposure. The AUC(0-2) for free and total BPA was 4.1-fold and 1.8-fold greater, respectively, in s.c. vs. oral delivery. While exposure route affected BPA metabolism, internal dosimetry following s.c. injection of 10 µg BPA/kg BW is similar to BPA levels observed in humans. Prostates from aged rats given s.c. or oral BPA neonatally and T+E implants as adults exhibited nearly identical, heightened susceptibility to PIN incidence and score as compared to neonatal oil-controls. These findings on prostate health are directly relevant to humans at current BPA exposure levels.

Estrogen receptor α and ß expressions in hypothalamus-pituitary-ovary axis in rats exposed lactationally to soy isoflavones and bisphenol A.

OBJECTIVES: This paper aims to investigate the uterotrophic activities of lactational exposure to combination of soy isoflavones (SIF) and bisphenol A (BPA) and to examine estrogen receptor α (ERα) and estrogen receptor ß (ERß) expressions in hypothalamus-pituitary-ovary axis and uterus. METHODS: Maternal rats that were breeding about 8 litters were randomly divided into four groups with seven dams in each group. Dams in different treatment groups received corn oil (control), 150 mg/kg BW of SIF, 150 mg/kg BW of BPA or combination of 150 mg/kg BW of SIF and 150 mg/kg BW of BPA, respectively, from postnatal day 5 to 11 (PND5-11) by gavage. On PND12 and PND70, 10 female litters were killed and hypothalamus, pituitary, ovary and uterus were collected. ERα and ERß expressions in these organs were detected with Western blotting assay. And vaginal opening time and estrus cycle were examined in animals fed for PND70. RESULTS: On PND12, the relative uterine weight of rats treated with ISF or BPA or their combination was significantly higher than that of untreated rats (P<0.05). But the relative uterine weight of rats in the co-exposure group was slightly lower than that in the group only exposed to SIF or BPA. On PND 70, however, the relative uterine weight in each treatment group was not statistically different from that in the control group (P>0.05). Vaginal opening time and estrus cycle in groups treated with SIF or BPA or their combination were similar to those in the control group (P>0.05). Exposure to SIF or BPA or their combination could up-regulate or down-regulate ERα and ERß expressions in hypothalamus, pituitary, ovary and uterus on PND12 and PND70. These regulation patterns for ERα and ERß were different in different organs at different time points. CONCLUSION: Lactational exposure to ISF or BPA or their combination could induce uterotrophic responses in neonate rats, which disappeared in later life. But these data fail to suggest a possibility for synergic actions between SIF and BPA. It was also demonstrated that the uterotrophic effects of SIF and BPA exposure might, at least, involve modification of ERα or ERß expressions in the hypothalamus-pituitary-ovary axis.