Seasonal transfer and quantification of urinary estradiol in the big brown bat (Eptesicus fuscus).

Growing evidence shows that sex steroids not only act within the individual whose glands produce them; they can also act on proximate conspecifics. Previous studies show that exogenous 17ß-estradiol (E2) can be absorbed both nasally and percutaneously, arriving in blood, neural, reproductive, and peripheral tissues. When male bats were injected with radiolabeled E2 (3H-E2) and housed with females during the mating season, radioactivity was reliably measured in the females' tissues. The present study was designed to compare E2 transfer from male to female bats at three time points in the annual reproductive cycle: spring (ovulation and fertilization), summer (maternal season), and autumn (mating season). Pairs of mature female bats were housed with a mature 3H-E2-treated male (50 µCi). Following 48 h of communal housing, radioactivity was measured in the tissues of female bats. Higher levels of radioactivity were present in the uterus and other tissues during the spring and autumn seasons compared to the summer season. We also measured natural levels of bioactive, unconjugated E2 in the urine of male bats using enzyme immunoassays, and found that it was present in all three seasons but at lower levels during the summer. Male-excreted E2 could transfer to females within the close confines of a roost, potentially influencing their reproductive physiology and behavior. These results suggest increased E2 transfer coincides with female reproduction, with urine as a likely vector. We suggest that sex steroid transfer among interacting individuals may explain several mammalian phenomena historically viewed as "pheromonal".

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

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.

A mixture of five endocrine-disrupting chemicals modulates concentrations of bisphenol A and estradiol in mice.

Most people in developed countries are exposed to multiple endocrine-disrupting synthetic chemicals. We previously showed that a single dose of triclosan, tetrabromobisphenol A (TBBPA), butyl paraben, propyl paraben, or di(2-ethylhexyl) phthalate elevated concentrations of bisphenol A (BPA) in mice. Here we investigated whether concurrent exposure to lower doses of these five chemicals could modulate concentrations of bisphenol A (BPA) or the natural estrogen, 17ß-estradiol (E2). CF1 mice were injected subcutaneously with 0.1 or 0.5 mg of one chemical, or a 0.5 mg mixture containing 0.1 mg of each of all five chemicals, then given dietary 50 µg kg-114C-BPA. The mixture elevated 14C-BPA concentrations in the lungs, muscle, uterus, ovaries, kidney, and blood serum of female mice. When administered alone, triclosan and TBBPA elevated 14C-BPA concentrations in the uterus, ovaries, and blood serum. In another experiment, CF1 mice were injected subcutaneously with the 0.5 mg mixture containing 0.1 mg of all five chemicals, then E2 was measured in urine 2-12 h later. The mixture elevated E2 at 8 h after injection in female mice. No treatments significantly altered concentrations of 14C-BPA or E2 in male mice. These data show that these endocrine-disrupting chemicals interact in vivo, magnifying one another's effects, consistent with inhibition of enzymes that are critical for estrogen metabolism. These findings highlight the importance of considering exposure to multiple chemicals when assessing health outcomes and determining regulatory exposure limits.

Influence of Tetrabromobisphenol A, with or without Concurrent Triclosan, upon Bisphenol A and Estradiol Concentrations in Mice.

BACKGROUND: Humans are commonly exposed to multiple environmental chemicals, including tetrabromobisphenol A (TBBPA; a flame retardant), triclosan (an antimicrobial agent), and bisphenol A (BPA; polycarbonate plastics). These chemicals are readily absorbed and may interact with each other. OBJECTIVES: We sought to determine whether TBBPA, given alone or in combination with triclosan, can modulate the concentrations of BPA and 17ß-estradiol (E2). METHODS: Female and male CF-1 mice were each given a subcutaneous injection of 0-27mg TBBPA, with or without concurrent 0.33mg triclosan, followed by dietary administration of 50µg/kg body weight 14C-BPA. Radioactivity was measured in blood serum and tissues through liquid scintillation counting. In subsequent experiments, female and male CF-1 mice were each given a subcutaneous injection of 0 or 1mg TBBPA and E2 was measured in urine 2-12 h after injection. RESULTS: Doses as low as 1mg TBBPA significantly elevated 14C-BPA concentrations in the uterus and ovaries of females; in the testes, epididymides, vesicular-coagulating glands, and preputial glands of males; and in blood serum, heart, lungs, and kidneys of both sexes; urinary E2 concentrations were also elevated. Lower doses of TBBPA or triclosan that had no effects on their own elevated 14C-BPA concentrations when the two substances were given concurrently. CONCLUSION: These data indicate that TBBPA, triclosan, and BPA interact in vivo, consistent with evidence that TBBPA and triclosan inhibit enzymes that are critical for BPA and E2 metabolism. https://doi.org/10.1289/EHP1329.

Diethylhexyl phthalate magnifies deposition of 14 C-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 14 C-BPA. Animals were dissected 1 h following 14 C-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 © 2017 John Wiley & Sons, Ltd.

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

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 17ß-estradiol (E2). Female and male CF1 mice were each given a subcutaneous injection of oil containing 0 (vehicle), 1, 3, or 9mg BP or PP, then given a dietary supplement containing 50µg/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, 3mg BP, or 3mg PP, and E2 was measured in urine 2-12h later. Whereas PP did not affect E2, BP significantly elevated E2 6-10h after injection in females and 8h 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.

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

Experiments using female mice and bats have demonstrated that tritium-labeled 17ß-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.

Sources of variance within and among young men in concentrations of 17ß-estradiol and testosterone in axillary perspiration.

The most potent estrogen, 17ß-estradiol (E2), and its precursor, testosterone (T), play critical roles in mammalian reproductive processes. Evidence indicates that these steroids are present in bioactive form in the excretions of many male mammals. It has been demonstrated that small lipophilic steroids such as E2 can be absorbed by proximate females from male excretions, arriving in the uterus, brain, and other organs where there are estrogen receptors. We took repeated samples of axillary perspiration from men aged 20-30years during vigorous exercise. Both steroids were consistently measurable, with concentrations that ranged from values comparable to those in facial perspiration and urine of both men and women to values that greatly exceeded concentrations observed in any other substrate of men and women. Inter-individual variance in axillary E2 was positively correlated with the extent of intimate experience with women, as assessed by a questionnaire, but unrelated to subjective measures of stress, exercise habits, or phytoestrogen content of diet. In addition, higher levels of axillary E2 were observed in participants when samples were collected by a female (as compared to a male) experimenter. These data are concordant with an hypothesis that male excretion of sex steroids could exert pro-reproductive influences on proximate females.

Concurrent administration of diethylhexyl phthalate reduces the threshold dose at which bisphenol A disrupts blastocyst implantation and cadherins in mice.

Many people are repeatedly exposed to both bisphenol A (BPA) and diethylhexyl phthalate (DEHP), but there has been little research concerning their effects in combination. Both can disrupt blastocyst implantation in inseminated females, albeit at high doses. We exposed mice on gestation days (GD) 1-4 to combinations of BPA and DEHP in doses below the threshold necessary to disrupt implantation on their own. On GD 6, there were fewer normally-developed implantation sites and more underdeveloped implantation sites in females given the combined subthreshold doses. Uterine epithelial cadherin (e-cadherin), a protein that assists in blastocyst adhesion to the uterine epithelium, was significantly reduced by these combined doses, but not by the individual doses. A similar trend was seen in integrin αvß3, another uterine adhesion molecule. Cadherin-11 was disrupted by BPA but not DEHP. These data are consistent with competition of BPA and DEHP for conjugating enzymes.

Absorption and distribution of estradiol from male seminal emissions during mating.

Estradiol-17ß (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.

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.

Stress lowers the threshold dose at which bisphenol A disrupts blastocyst implantation, in conjunction with decreased uterine closure and e-cadherin.

Exposure to stress can disrupt blastocyst implantation in inseminated female mice, and evidence implicates elevation of the female's estrogen:progesterone ratio. Exposure to the xenoestrogen, bisphenol A (BPA) can also disrupt implantation. Undisturbed control female CF-1 mice were compared to other females that were exposed to predators (rats) across a wire-mesh grid during gestation days (GD) 1-4, a procedure that elevates corticosterone but does not on its own disrupt implantation in this genetic strain. They were concurrently exposed to varied doses of BPA that on their own were below the threshold dose sufficient to disrupt implantation. On GD 6, we measured the number of intrauterine implantation sites and extracted their uteri, which subsequently were stained and analyzed for uterine luminal area and epithelial cadherin (e-cadherin), a molecule that causes uterine closure and adhesion of blastocysts to the uterine epithelium. The combination of rat-exposure stress and BPA significantly disrupted implantation and increased uterine luminal area, whereas either manipulation on its own did not. E-cadherin was significantly reduced by exposure to BPA, positively correlated with the number of implantation sites, and inversely correlated with luminal area. BPA exposure was also associated with nonmonotonic perturbation of urinary corticosterone concentrations and increased urinary estradiol concentrations on GD 6. These data are consistent with a potential summation of stress-induced estrogen and xenoestrogen activity.

Sex steroids as pheromones in mammals: the exceptional role of estradiol.

This article is part of a Special Issue (Chemosignals and Reproduction). Whether from endogenous or exogenous sources, 17ß-estradiol (E2) has very powerful influences over mammalian female reproductive physiology and behavior. Given its highly lipophilic nature and low molecular mass, E2 readily enters excretions and can be absorbed from exogenous sources via nasal, cutaneous, and other modes of exposure. Indeed, systemic injection of tritiated estradiol ((3)H-E2) into a male mouse or bat has been shown to produce significant levels of radioactivity in the reproductive tissues and brain of cohabiting female conspecifics. Bioactive E2 and other steroids are naturally found in male mouse urine and other excretions, and males actively direct their urine at proximate females. Very low doses of E2 can mimic the Bruce effect (disruption of peri-implantation pregnancy by novel males), the Vandenbergh effect (early reproductive maturation induced by novel males), and male-induced estrus and ovulation. Males' capacities to induce the Bruce and Vandenbergh effects can both be diminished by manipulations that reduce their urinary E2. Uterine dynamics during the Bruce and Vandenbergh effects are consistent with the actions of E2. Collectively, these data demonstrate a critical role of male-sourced E2 in these major mammalian pheromonal effects.

Estradiol transfer from male big brown bats (Eptesicus fuscus) to the reproductive and brain tissues of cohabiting females, and its action as a pheromone.

The powerful estrogen, 17ß-estradiol, has been found to pass from male excretions to the reproductive organs, brain, and other tissues of cohabiting females in laboratory mice. The current studies were designed to examine whether this phenomenon also occurs in big brown bats (Eptesicus fuscus), a mammal appropriate for testing cross-species generality because of its phylogenetic distance from mice. When tritiated estradiol ((3)H-E2) was administered directly on the nasal area of adult female bats, radioactivity was reliably observed in the uterus and ovaries, and also in the brain and other tissues. When (3)H-E2 was applied to the skin, radioactivity was observed in reproductive and other peripheral tissues. We injected male bats with minute quantities of (3)H-E2 and housed each of them directly with groups of adult females for 48h. We then measured radioactivity in male and female bat tissues. In each of several replications of one male housed with three females, radioactivity was reliably observed in the uterus of all females, and in many other tissues in almost every female. Measurement in the organs of males directly exposed to (3)H-E2 showed high levels of radioactivity in the testes and especially the epididymides. These data indicate that estradiol is transferred from males to females, likely via absorptions from males' excretions and potentially also via intravaginal exposure during mating. Given the potency of estradiol in regulating female reproductive physiology and behavior, our data strongly suggest the potential for pheromonal action whereby male mammals induce sexual receptivity and ovulation in females.

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 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.

Novel male exposure reduces uterine e-cadherin, increases uterine luminal area, and diminishes progesterone levels while disrupting blastocyst implantation in inseminated mice.

Exposure to novel male mice disrupts blastocyst implantation in inseminated female mice, and evidence increasingly implicates the female's absorption of male urinary estrogens. We observed implantation sites in male-exposed and isolated control female mice during gestation days (GD) 2-8, observing a significant reduction in male-exposed females compared to controls, particularly on GD 6 and 8. We also measured transitions in uterine luminal area and e-cadherin expression, as these processes are modulated by estrogens. Luminal area was greater in male-exposed females than in controls during the post-implantation period (GD 5-7). E-cadherin levels were suppressed by male exposure, particularly during GD 4-6 Serum progesterone levels were also reduced in male-exposed females. The effects of male exposure on uterine closure and e-cadherin levels are consistent with established effects of estrogens, and suggest a possible mechanism that could contribute to implantation failure. This article is part of a Special Issue entitled 'Pregnancy and Steroids'.

Estrogen-progesterone balance in the context of blastocyst implantation failure induced by predator stress.

Diverse stressors can disrupt blastocyst implantation in inseminated female mammals. Stress-induced implantation failure can be mimicked by minute doses of exogenous estradiol, and some evidence indicates that it may be mitigated by exogenous progesterone. In Experiment 1, we showed that acute exposure to a rat across a wire-mesh grid caused elevation of corticosterone and progesterone. In Experiment 2, we showed that exposure of inseminated mice to rats across a grid during gestation days 1-5 was associated with avoidance of proximity to the grid and a significantly reduced number of implantation sites on gestation day 6. Rat-exposure also resulted in elevated progesterone levels in females that maintained their pregnancies, and elevated estradiol levels in females that lost their pregnancies. In Experiment 3, we investigated whether exogenous progesterone, estradiol, or a combination of both could influence implantation failure induced by rat-exposure stress. Treatment with 100 ng estradiol per day on gestation days 1-5 induced a complete absence of implantation sites on gestation day 6, regardless of the presence or absence of the stressor. Administration of 500 µg progesterone per day was insufficient to prevent the stress-induced pregnancy loss. However, 500 µg progesterone plus 10 ng estradiol per day did prevent implantation failure in rat-exposed females. These findings are consistent with the hypothesis that estradiol elevations contribute to stress-induced pregnancy loss, but show paradoxically that low doses of estradiol can act together with progesterone to mitigate stress-induced pregnancy loss.

Perturbation of male sexual behavior in mice (Mus musculus) within a discrete range of perinatal bisphenol-A doses in the context of a high- or low-phytoestrogen diet.

Differentiation of masculine and feminine behavior in mammals depends on perinatal sex steroids. As bisphenol-A (BPA) can be estrogenic and anti-androgenic, we examined impacts of perinatal exposure upon adult sexual behavior and morphology of male mice. In Experiment 1, dams were fed either a high- or low-phytoestrogen diet and received daily oral doses of 0, 0.175, 1.75, or 17.5µg BPA from gestation day 10 through post-partum day 9. Male offspring from the high-phytoestrogen plus 17.5µg BPA condition showed reduced mass of vesicular-coagulating but not other male glands, and showed increased latency to insemination when paired with females. In Experiment 2, these procedures were replicated but with all animals fed the high-phytoestrogen diet and perinatal BPA doses of 0, 17.5, 175, or 1750µg/day. Adult masses of testes and male-accessory glands and levels of urinary steroids were not significantly affected. When males each encountered a sexually receptive female, there were fewer intromissions among those given 17.5 or 175µg and fewer ejaculations among those given 17.5µg, but the 1750µg dose had no effect. Perinatal BPA dosages thus influenced male sexual behavior non-monotonically, with impairment evident in a discrete dose range among males on a high-phytoestrogen diet.

Transfer of [³H]estradiol-17ß and [³H]progesterone from conspecifics to cohabiting female mice.

Estradiol-17ß (E2) and progesterone (P4) play critical roles in female reproductive physiology and behavior. Given the sensitivity of females to exogenous sources of these steroids, we examined the presence of E2 and P4 in conspecifics' excretions and the transfer of excreted steroids between conspecifics. We paired individual adult female mice with a stimulus male or female conspecific given daily injections of [³H]E2 or [³H]P4. Following 48  h of direct interaction with the stimulus animal, we measured radioactivity in the uterus, ovaries, muscle, olfactory bulbs, mesencephalon and diencephalon (MC+DC), and cerebral cortex of the untreated female cohabitant. Radioactivity was significantly present in all tissues of female subjects after individual exposure to a stimulus male or female given [³H]E2. In females exposed to males given [³H]P4, radioactivity was significantly present in the uterus, ovaries, and muscle, but not in other tissues. In females exposed to stimulus females given [³H]P4, radioactivity was significantly present in all tissues except the MC+DC. In mice directly administered [³H]steroids, greater radioactivity was found in the urine of females than of males. Among females directly administered [³H]steroids, greater radioactivity was found in urine of those given [³H]P4 than of those given [³H]E2. When females were administered unlabeled E2 before exposure to [³H]E2-treated females, less radioactivity was detected in most tissues than was detected in the tissues of untreated females exposed to [³H]E2-treated females. We suggest that steroid transfer among individuals has implications for the understanding of various forms of pheromonal activity.