Tyler Pollock

Triclosan exacerbates the presence of 14C-bisphenol A in tissues of female and male mice

Current human generations are commonly exposed to both triclosan (TCS), an antimicrobial agent, and bisphenol A (BPA), the monomer of polycarbonate plastics and epoxies. Both are readily absorbed into circulation and found distributed among diverse tissues. Potential interactions between TCS and BPA are largely unstudied. We investigated whether TCS exposure affects the distribution of ingested (14)C-BPA in select tissues. CF-1 mice were each subcutaneously injected with TCS then orally administered 50 μg/kg (14)C-BPA. Females received 0, 0.2, 0.6, 1, 2, or 18 mg TCS (equivalent respectively to 0, 6.3, 16.9, 30.1, 60.5, and 558.9 mg/kg). Males received 0, 0.2, 2, or 18 mg TCS (equivalent respectively to 0, 5.3, 53.4, and 415.0mg/kg). Levels of radioactivity were measured through liquid scintillation counting in blood serum and brain, reproductive, and other tissues. Significantly elevated levels of radioactivity were observed following combined TCS and (14)C-BPA administration, with minimally effective TCS doses being tissue-dependent (Females: lungs, 0.6 mg; uterus, 1mg; heart, muscle, ovaries, and serum, 18 mg. Males: serum, 0.2mg; epididymides, 2mg). Subsequently, we found that 2 or 6 mg TCS increased radioactivity in the ovaries and serum of females orally given only 5 μg/kg (14)C-BPA. These data indicate that TCS can interact with BPA in vivo, magnifying its presence in certain tissues and serum. The data are consistent with evidence that TCS utilizes enzymes that are critical for metabolism and excretion of BPA. Further research should investigate the mechanisms through which these two chemicals interact at environmentally-relevant doses.

Presence and bioavailability of bisphenol A in the uterus of rats and mice following single and repeated dietary administration at low doses.

This research examined the distribution of low dietary doses of bisphenol A (BPA). When female rats received 50μg/kg (14)C-BPA orally, radioactivity was distributed throughout the body, with especial presence in the uterus. Pre-treatment with estradiol or the estrogen antagonist ICI 182,780 significantly reduced radioactivity in the uterus. The majority of BPA at the uterus was determined to be aglycone (receptor-active) via GC-MS. Subsequently, mice given 0.5, 5, or 50μg/kg (14)C-BPA showed more radioactivity in the uterus than in other non-metabolic tissues. When female mice received 1, 7, or 28 daily doses of 50μg/kg (14)C-BPA, then were measured 24h after the last dose, significantly more radioactivity was detected in the uterus, liver, and kidney following repeated doses. Collectively, these data provide evidence for the in vivo interaction of BPA with estrogen receptors. They also indicate elevated presence of BPA in reproductive tissues after repeated low doses.

Triclosan elevates estradiol levels in serum and tissues of cycling and peri-implantation female mice

Triclosan, an antimicrobial agent added to personal care products, can modulate estrogenic actions. We investigated whether triclosan affects concentrations of exogenous and endogenous estradiol. Female mice were given injections of triclosan followed by 1μCi tritium-labeled estradiol. Mice given daily 2-mg triclosan doses (57.9mg/kg/dose) showed significantly elevated radioactivity in tissues and serum compared to controls. A single dose of 1 or 2mg triclosan increased radioactivity in the uterus in both cycling and peri-implantation females. We also measured natural urinary estradiol at 2-12h following triclosan injection. Unconjugated estradiol was significantly elevated for several hours following 1 or 2mg of triclosan. These data are consistent with evidence that triclosan inhibits sulfonation of estrogens by interacting with sulfotransferases, preventing metabolism of these steroids into biologically inactive forms. Elevation of estrogen concentrations by triclosan is potentially relevant to anti-reproductive and carcinogenic actions of excessive estrogen activity.

Butyl paraben and propyl paraben modulate bisphenol A and estradiol concentrations in female and male mice

ABSTRACT People are routinely exposed to the antimicrobial preservatives butyl paraben (BP) and propyl paraben (PP), as well as the monomer of polycarbonate plastics, bisphenol A (BPA). These chemicals are reliably detected in human urine and potentially interact. We investigated whether BP or PP exposure can modulate the concentrations of 14C‐BPA and 17&bgr;‐estradiol (E2). Female and male CF1 mice were each given a subcutaneous injection of oil containing 0 (vehicle), 1, 3, or 9 mg BP or PP, then given a dietary supplement containing 50 &mgr;g/kg 14C‐BPA. Radioactivity was measured in tissues through liquid scintillation counting. Significantly elevated 14C‐BPA concentrations were observed following BP treatment in blood serum of both sexes, as well as the lungs, uterus, and ovaries of females and the testes and epididymides of males. Treatment with PP significantly elevated 14C‐BPA concentrations in the uterus only. In another experiment, female and male CF1 mice were each injected with vehicle, 3 mg BP, or 3 mg PP, and E2 was measured in urine 2–12 h later. Whereas PP did not affect E2, BP significantly elevated E2 6–10 h after injection in females and 8 h after injection in males. These data indicate that BP and PP can alter the pharmacokinetics of BPA in vivo, and that BP can modulate E2 concentrations. These results are consistent with evidence that parabens inhibit enzymes that are critical for BPA and E2 metabolism, and demonstrate the importance of considering concurrent exposure to multiple chemicals when determining regulatory exposure limits. HIGHLIGHTSWe studied whether paraben exposure affects the distribution of oral 14C‐BPA.Elevated 14C–BPA was observed in mice given butyl or propyl paraben.We also studied whether paraben exposure affects natural E2 levels in urine.Elevated E2 was observed in mice given butyl, but not propyl, paraben.Parabens may compete for enzymes that are critical for BPA and E2 metabolism.

Absorption and distribution of estradiol from male seminal emissions during mating

Estradiol-17β (E2) plays critical roles in female maturation, sexual receptivity, ovulation and fertility. In many mammals, contact with males can similarly affect these female parameters, whereas male excretions contain significant quantities of E2. We administered radiolabeled estradiol ([3H]E2) to male mice in doses representing a small fraction of their endogenous E2. These males were paired with sexually receptive females, and radioactivity was traced into the females’ systems. In Experiment 1, males were given [3H]E2 at 24 and 1 h before mating. Male-to-female [3H]E2 transfer intensified with increasing numbers of intromissions and spiked in the uterus after insemination. In Experiment 2, sexually experienced young males received [3H]E2 at 72 and 24 h before mating, and all mated to ejaculation. The copulatory plug deposited in the female reproductive tract contained substantial levels of radioactivity. The uteri, other tissues and blood serum of females displayed radioactivity indicative of E2 transfer. In Experiment 3, radioactivity was observed 3 and 18 h after insemination in the females’ uteri and other tissues, including parts of the brain. In Experiment 4, we observed substantial levels of radioactivity in semen as well as the copulatory plugs retrieved from the females after mating. Transferred E2 could directly affect abundant estrogen receptors in the female reproductive tract without potential metabolism by the liver. Sexually transferred E2 may facilitate uterine preparation for blastocyst implantation. These data converge with several lines of evidence indicating that male-sourced E2 can transfer to proximate females in bioactive form, contributing to various mammalian pheromonal effects.

Diethylhexyl phthalate magnifies deposition of 14C–bisphenol A in reproductive tissues of mice

Endocrine disrupting chemicals are found in diverse common products, including cosmetics, food packaging, thermal receipt paper and plastic containers. This exposes most people in developed countries through ingestion, skin absorption and inhalation. Two ubiquitous endocrine disrupting chemicals, bisphenol A (BPA) and diethylhexyl phthalate (DEHP) can interact in disrupting blastocyst implantation in inseminated females. We hypothesized that DEHP might increase the bioavailability of BPA in tissues by competing for metabolic enzymes. We injected 0, 3, 9 or 18 mg DEHP into female and male mice and allowed 30 min for the chemical to circulate before giving them a food supplement containing 50 μg kg−1 14C–BPA. Animals were dissected 1 h following 14C–BPA administration and various tissue samples were acquired. Samples were solubilized and radioactivity was measured via liquid scintillation counting. In cycling females, DEHP increased BPA deposition in the muscle, uterus, ovaries and blood serum relative to controls. In peri‐implantation females, DEHP increased deposition of BPA in the uterus, ovaries and serum relative to controls. In males, DEHP doses increased BPA deposition in serum and epididymis relative to controls. These results are consistent with the hypothesis that DEHP competes with BPA for conjugating enzymes such as UDP‐glucuronosyltransferase, thereby magnifying the presence of BPA in estrogen‐binding reproductive tissues. Copyright

Progesterone transfer among cohabitating female big brown bats (Eptesicus fuscus)

Experiments using female mice and bats have demonstrated that tritium-labeled 17β-estradiol (3H-E2) can be absorbed via cutaneous and intranasal routes and distributed to reproductive and neural tissues. Radioactivity has also been measured in tissues of untreated females after 48h cohabitation with 3H-E2 injected males. The present study was designed to quantify steroid transfer among female bats. Radioactive quantification via liquid scintillation counting revealed absorption of tritium-labeled progesterone (3H-P4) in adult females 1h after cutaneous and intranasal application (10μCi). Subsequently, pairs of mature females were each housed for 48h with a single mature female that had been administered 3H-P4 (50μCi) via intraperitoneal injection. Radioactivity was observed in all collected tissues of all non-injected females at levels significantly greater than the control group. Following the same paradigm, radioactivity was not observed in the tissues of untreated female bats that were housed with stimulus females treated with 3H-E2 (50μCi). Enzyme immunoassays revealed measurable levels of unconjugated progesterone and estradiol in the urine of female bats, suggesting urine as a vector for steroid transfer. Given that bats of this species live in predominantly female roosts in very close contact, progesterone transfer among individuals is likely to occur in natural roosts.

Bisphenol S modulates concentrations of bisphenol A and oestradiol in female and male mice

Abstract Concern over endocrine-disrupting actions of bisphenol A (BPA) has prompted some manufacturers to remove it from consumer products. Among the chemical replacements in “BPA-free” products are other bisphenol analogues, such as bisphenol S (BPS). Given evidence that BPA and BPS possess similar oestrogenic activity, their capacity to interact and disrupt oestrogen homeostasis should be examined. We investigated whether BPS can modulate concentrations of 14C-BPA, exogenous 3H-oestradiol (E2), or natural E2. CF-1 mice were each given a single subcutaneous injection of oil containing 0 (vehicle), 1, 3, or 9 mg BPS, then given a dietary supplement containing either 50 μg/kg 14C-BPA or 5 μCi (14.5 ng) 3H-E2. BPS treatment elevated 14C-BPA concentrations in blood serum and certain reproductive organs of both sexes, but reduced 3H-E2 concentrations in blood serum of females. In another experiment, natural E2 was measured in urine 2–12 h after injection of 0 (vehicle), 1, or 3 mg BPS. BPS reduced E2 concentrations at 10 h after injection in both sexes. These results are consistent with evidence that BPS and BPA compete for access to metabolic enzymes, and that BPS can disrupt oestrogen homeostasis. These findings demonstrate the importance of considering multiple toxicants when determining regulatory exposure limits.