The estrogenicity of bisphenol A-related diphenylalkanes with various substituents at the central carbon and the hydroxy groups

Application of liquid chromatography-mass spectrometry to the quantification of bisphenol A in human semen

The potential risks to human health and reproduction from the xenoestrogen bisphenol A (BPA) have not been well established. This is due in part to the absence of accurate analytical methods to quantify BPA in biological samples. In this study we establish an accurate, sensitive and selective analytical method for the quantification of BPA in human semen. To quantify BPA we compared the techniques of liquid chromatography-mass spectrometry (LC-MS) and enzyme-linked immunosorbent assay (ELISA). In addition we have taken steps to eliminate BPA contamination during sample extraction and preparation. Results show that the ELISA method gives an over-estimate of BPA concentration, which may be due, at least in part, to non-specific interactions with the BPA-antibodies. LC-MS gave much more accurate results and proved to be more sensitive with a detection limit of 0.5 ng ml(-1) compared to 2.0 ng ml(-1) by ELISA.

Acute toxicity, mutagenicity, and estrogenicity of bisphenol-A and other bisphenols

Although abundant data are available on the toxicity of bisphenol-A (2,2-bis (4-hydroxydiphenyl)propane; BPA), little is known about the toxicities of the structurally similar compounds, namely bisphenols (BPs). A variety of BPs were examined for their acute toxicity against Daphnia magna, mutagenicity, and estrogenic activity using the Daphtoxkit (Creasel Ltd.), the umu test system, and the yeast two-hybrid system, respectively, in comparison with BPA. BPA was moderately toxic to D. magna (48-h EC50 was 10 mg/l) according to the current U.S. EPA acute toxicity evaluation standard, and it was weakly estrogenic with 5 orders of magnitude lower activity than that of the natural estrogen 17 beta-estradiol in the yeast screen, while no mutagenicity was observed. All seven BPs tested here showed moderate to slight acute toxicity, no mutagenicity, and weak estrogenic activity as well as BPA. Some of the BPs showed considerably higher estrogenic activity than BPA, and others exhibited much lower activity. Among the tested BPs, two compounds, i.e., bisphenol-S (bis(4-hydroxydiphenyl)sulfone) and bis(4-hydroxyphenyl)sulfide, have never been reported for their estrogenic activity previously.

Structure-activity relationships for gene activation oestrogenicity: evaluation of a diverse set of aromatic chemicals

Structure-activity relationships for oestrogenicity were developed based on 120 aromatic chemicals evaluated in the Saccharomyces cerevisiae-based Lac-Z reporter assay. Relative gene activation was compared to 17 beta-estradiol and varied over eight orders of magnitude. Analysis of the data compared to 17 beta-estradiol identified three structural criteria that were related to xenoestrogen activity and potency: (1) the hydrogen-bonding ability of the phenolic ring mimicking the A-ring, (2) a hydrophobic centre similar in size and shape to the B- and C-rings, and (3) a hydrogen-bond donor mimicking the 17 beta-hydroxyl moiety of the D-ring, especially with an oxygen-to-oxygen distance similar to that between the 3- and 17 beta-hydroxyl groups of 17 beta-estradiol. Binding data were segregated into activity clusters including strong, moderate, weak, and detectable gene expression, and those compounds that were inactive. The hydrogen-bonding ability of hydroxy group in the 3-position on 17 beta-estradiol was observed to be essential for gene activation. Compounds with a 4-hydroxyl substituted benzene ring and a hydrophobic moiety of size and shape equivalent to the B-ring of 17 beta-estradiol were generally observed to be weakly active compounds. Moderately active compounds have a 4-hydroxyl substituted benzene ring with a hydrophobic moiety equivalent in size and shape to the B- and C-ring of 17 beta-estradiol, or have a high hydrogen-bond donor capacity owing to the presence of halogens on a nonphenolic ring. Strongly active compounds, similar to 4,4'-diethylethylene bisphenol (DES), possess the same hydrophobic ring structure as described for moderately active compounds and an additional hydroxyl group with an oxygen-to-oxygen distance close to that exhibited by the 3- and 17-hydroxyl groups of 17 beta-estradiol.

Quantitative detection of bisphenol A and bisphenol A diglycidyl ether metabolites in human plasma by liquid chromatography-electrospray mass spectrometry

Due to the ubiquity of epoxy resin compounds and their potential role in increasing the risk for reproductive dysfunction and cancer, the need for an assessment of human exposure is urgent. Therefore, we developed a method for measuring bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) metabolites in human blood samples using high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-MS). Human blood samples were processed using enzymatic deconjugation of the glucuronides followed by a novel sample preparation procedure using a solid-phase-cartridge column. This selective analytical method permits rapid detection of the metabolites, free BPA and a hydrolysis product of BADGE (BADGE-40H) with detection limits in the low nanogram per milliliter range (0.1 ng ml(-1) of BPA and 0.5 ng ml(-1) of BADGE-40H). The sample extraction was achieved by Oasis HLB column on gradient elution. The recoveries of BPA and BADGE-40H added to human plasma samples were above 70.0% with a standard deviation of less than 5.0%. This selective, sensitive and accurate method will assist in elucidating potential associations between human exposure to epoxy-based compounds and adverse health effects.

Morphological effects of Bisphenol-A on the early life stages of medaka (Oryzias latipes)

Bisphenol-A (BPA), a widely used polycarbonate plasticizer, has been of concern because it has been shown to leach out of plastics and other epoxy products. Primary sources of environmental releases are expected to be from BPA and epoxy manufacturing facilities. Although environmental concentrations may be limited, little is known about the effects of this compound on fish, particularly during their most sensitive early life stages. A pilot study exposing newly hatched medaka to 200 microg BPA/l for 96 h showed to be non-lethal. In addition, medaka embryos were exposed beginning at 5 h post-fertilization, for 9 days at 25 degrees C, to concentrations of 20 or 200 microg BPA/l (24 h static renewal). Embryos were monitored daily for development and gross abnormalities. Embryos exposed to 200 microg BPA/l did not exhibit abnormalities until after day 4. However, between days 4 and 8 the severity index (SI) score of embryos was significantly greater than those exposed to lesser concentrations. By day 9, SI scores were not statistically different among treatments. BPA caused transient embryonic deformities in medaka at environmentally relevant concentrations.

Development of sensitive high-performance liquid chromatography with fluorescence detection using 4-(4,5-diphenyl-1H-imidazol-2-yl)-benzoyl chloride as a labeling reagent for determination of bisphenol A in plasma samples

A sensitive HPLC method for determination of bisphenol A (BPA) in plasma samples using 4-(4,5-diphenyl-1H-imidazol2-yl)benzoyl chloride (DIB-Cl) as a fluorescence labeling reagent was developed. The fluorescence labeling reaction was completed within 10 min at room temperature. DIB-Cl reacts with the phenolic hydroxyl group of BPA in the presence of triethylamine (TEA). The DIB-Cl derivative of BPA (DIB-BPA) was separated within 30 min with an ODS column using acetonitrile-water (90:10, v/v) as the isocratic eluent. Calibration graphs were linear over the range of 1.0-100 ng/ml (r=0.999). The detection limit of DIB-BPA was 0.05 ng/ml (2.5 pg) at a signal-to-noise ratio of 3. The relative standard deviations (RSDs) of the method for between-run were 1.0-5.0%. The analytical recoveries of known amounts (1.0 and 100 ng/ml) of BPA-spiked rabbit plasma were around 95%.

Measurement of estrogenic activity of chemicals for the development of new dental polymers

The estrogenic activities of 13 Bisphenol-A (BPA)-related chemicals for development of new polymers by three in vitro bioassay have been examined in the presence and absence of a post-mitochondrial metabolizing system (S9 mix). BPA, Bisphenol-B (BPB), Bisphenol-F (BPF), Bisphenol-S (BPS), 4,4-ethylidenebisphenol (BP1), 4,4-dihydroxybenzophenone (BP2), 2,2-bis (4-hydroxyphenyl)-hexafluoropropane (BP3), 4,4-(1,4-phenylenediisopropylidene) bisphenol (BP4), 4,4-cyclohexylidenebisphenol (BP5), 4,4-dihydroxydiphenyl ether (BP6), 4-hydroxydiphenylmethane (BP7), 4-cumylphenol (BP8) and 4,4-dihydroxydiphenyl sulfide (BP9) were each diluted with dimethyl sulfoxide to final concentrations ranging from 10(-7) to 10(-3) M in both the yeast two-hybrid system and in a fluorescence polarization system. Dilutions of 10(-9) to 10(-4) M were assayed in the E-screen, respectively. Except for BPS and BP4, the chemicals tested showed estrogenic activity in the absence of cut S9 mix preparation and the activity was enhanced with S9 mix. BPS, which was initially negative, was active with S9 mix in the yeast two-hybrid system. BP2 was weakly estrogenic with or without S9 mix. Chemicals other than BP2 were positive in the competition binding assay. All chemicals tested showed estrogenic activity in the E-screen, the concentration level of which was 10(4) times lower than those of the other two assays.

Potential estrogenic effects of bisphenol-A estimated by in vitro and in vivo combination assays

The potential estrogenic activities of bisphenol-A were investigated in vitro (E-screen and estrogen receptor competitive binding bioassays) and in vivo (uterotrophic assay). Uterotrophic responses were evaluated using mature ovariectomized Sprague-Dawley female rats treated subcutaneously with bisphenol A (1, 5, 10, 50, and 100 mg/kg/day), E2 (0.3 microgram/kg), and DES (0.3 microgram/kg) for 3 consecutive days. In a MCF-7 cell proliferation assay, E2 and DES used as positive estrogens induced maximum proliferation of MCF-7 cells at 1.0 nM, whereas BPA slightly induced MCF-7 cell proliferation at a higher level of 0.1 microM and maximum proliferation at 10 microM. In a competitive binding assay, E2 and DES showed inhibition of 17 beta-[3H]estradiol binding to the rat uterus ER with an IC50 of 1.0 nM and 0.5 nM, respectively. However, BPA had an IC50 of 5 microM, which was approximately 5,000 or 10,000-fold greater than the IC50 of E2 and DES. In uterotrophic assays, uterus (wet and blotted) and vagina weights were significantly increased at the dose of BPA 100 mg/kg/day in OVX Sprague-Dawley rats. These studies demonstrate that BPA exhibits weak estrogenic activity in all experimental systems, and thus its migration from epoxy resins or polycarbonate products should be controlled not to exceed a safety levels for humans.

The induction of micronuclei in vitro by unpolymerized resin monomers

Components of resin materials may damage DNA, leading to genetic alterations in mammalian cells. Here, monomers were analyzed for the induction of chromosomal aberrations indicated by micronuclei induced in V79 cells. A dose-related increase in the numbers of micronuclei was observed with triethyleneglycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA), and glycidyl methacrylate (GMA). These effects were reduced, however, by a metabolically active microsomal fraction from rat liver. The very low activity of Bis-GMA and UDMA and the elevated numbers of micronuclei caused by high concentrations of methyl methacrylate and bisphenol A were associated with cytotoxicity. Our findings provide evidence for the induction of micronuclei by TEGDMA, HEMA, and GMA under physiological conditions, indicating clastogenic activity of these chemicals in vitro. Since it has been shown that TEGDMA also caused gene mutations and DNA sequence deletions in mammalian cells, the activity of this substance should be analyzed in vivo.

Simultaneous determination of phenolic xenoestrogens by solid-phase extraction and high-performance liquid chromatography with fluorescence detection

A highly sensitive and selective method for simultaneous determination of some hydroxyl group-containing endocrine disruptors, including bisphenol A (BPA), bisphenol B (BPB), bisphenol E (BPE), bisphenol F (BPF) and 4-nonylphenol (4-NP), was developed. The method consists of precolumn derivatization of the analytes, solid-phase extraction (SPE) and subsequent chromatographic analysis by high-performance liquid chromatography (HPLC) with fluorescence detection. 4,4'-Cyclohexylidenebisphenol (BPZ) was used as an internal standard. Derivatization was carried out using 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label. Parameters of the derivatization reaction (temperature, time, concentration of reagent, stability, etc.) and of the solid-phase extraction (recovery, solvent, etc.) were studied in detail. Detection limits of compounds studied in standard solutions ranged from 0.08-1.3 ppb (ng/ml). The proposed method was successfully applied to plastic samples; BPA was found in both polycarbonate and polyvinyl chloride plastics, while 4-NP was found in plastics made of polyvinyl chloride and another polymer.

In vitro estrogenicity of polybrominated diphenyl ethers, hydroxylated PDBEs, and polybrominated bisphenol A compounds

Polybrominated diphenyl ethers (PBDEs) are used in large quantities as additive flame retardants in plastics and textile materials. PBDEs are persistent compounds and have been detected in wildlife and in human adipose tissue and plasma samples. In this study, we investigated the (anti)estrogenic potencies of several PBDE congeners, three hydroxylated PBDEs (HO-PBDEs), and differently brominated bisphenol A compounds in three different cell line assays based on estrogen receptor (ER)-dependent luciferase reporter gene expression. In human T47D breast cancer cells stably transfected with an estrogen-responsive luciferase reporter gene construct (pEREtata-Luc), 11 PBDEs showed estrogenic potencies, with concentrations leading to 50% induction (EC(50)) varying from 2.5 to 7.3 microM. The luciferase induction of the most potent HO-PBDE [2-bromo-4-(2,4,6-tribromophenoxy)phenol] exceeded that of estradiol (E(2)), though at concentrations 50,000 times higher. As expected, brominated bisphenol A compounds with the lowest degree of bromination showed highest estrogenic potencies (EC(50) values of 0.5 microM for 3-monobromobisphenol A). In an ER alpha-specific, stably transfected human embryonic kidney cell line (293-ER alpha-Luc), the HO-PBDE 4-(2,4,6-tribromophenoxy)phenol was a highly potent estrogen with an EC(50) < 0.1 microM and a maximum 35- to 40-fold induction, which was similar to E(2). In an analogous ER beta-specific 293-ER betas-Luc cell line, the agonistic potency of the 4-(2,4,6-tribromophenoxy)phenol was much lower (maximum 50% induction compared to E(2)), but EC(50) values were comparable. These results indicate that several pure PBDE congeners, but especially HO-PBDEs and brominated bisphenol A-analogs, are agonists of both ER alpha and ER beta receptors, thus stimulating ER-mediated luciferase induction in vitro. These data also suggest that in vivo metabolism of PBDEs may produce more potent pseudoestrogens.

Comparative QSAR: on the toxicology of the phenolic OH moiety

In this report we consider the effect of substituents on phenol toxicity and show how the parameters used in Quantitative Structure-Activity Relationships (QSAR) can be used to draw mechanistic inferences of value in understanding the reasons behind the various types of toxicity. In particular, we are interested in gaining clearer insight into mechanisms via the Hammett-type parameters sigma, sigma(-), sigma(+) and octanol/water parti tion coefficients. Particular attention is given to the role of radical reactions and their role in attacking DNA to cause cancer or estrogenic toxicity.

Removal of estrogenic activities of bisphenol A and nonylphenol by oxidative enzymes from lignin-degrading basidiomycetes

Bisphenol A (BPA) and nonylphenol (NP) were treated with manganese peroxidase (MnP) and laccase prepared from the culture of lignin-degrading fungi. Laccase in the presence of 1-hydroxybenzotriazole (HBT), the so-called laccase-mediator system, was also applied to remove the estrogenic activity. Both chemicals disappeared in the reaction mixture within a 1-h treatment with MnP but the estrogenic activities of BPA and NP still remained 40% and 60% in the reaction mixtures after a 1-h and a 3-h treatment, respectively. Extension of the treatment time to 12 h completed the removal of estrogenic activities of BPA and NP. The laccase has less ability to remove these activities than MnP, but the laccase-HBT system was able to remove the activities in 6 h. A gel permeation chromatography (GPC) analysis revealed that main reaction products of BPA and NP may be oligomers formed by the action of enzymes. Enzymatic treatments extended to 48 h did not regenerate the estrogenic activities, suggesting that the ligninolytic enzymes are effective for the removal of the estrogenic activities of BPA and NP.

Quantitative assessment of estrogenic activity in the water environment of Korea by the E-SCREEN assay

In this study, the E-SCREEN assay was optimized and validated for the sensitive quantitative determination of the total estrogenicity in river samples. River water and sediment samples were collected and analyzed with the E-SCREEN. River water (10 l) was extracted using combined solid-phase extraction in static adsorption mode with Soxhlet extraction. Estrogenic pollutants adsorbed to the XAD-4 resin were recovered with 98.24 +/- 5.90% efficiency by elution with ethyl acetate and dichloromethane (1:9). The detection limit by 17beta-estradiol equivalent concentration (EEQ) of the E-SCREEN assay was 8.03 pg EEQ/l. Among the water samples, the estrogenic activity was observed to be higher downstream of the Kumho river (7.43 ng EEQ/l) and upstream of Kum river (2.05 ng EEQ/l) than in other samples. More than 3 mg of equivalent sediment samples from the Kumho river, Kum river and Miho stream showed partial agonistic effects, and the Mankyung river showed a partial agonistic effect with only 1.5 mg of sediment. The highest value of RPE was 83.34 downstream of the Kumho river, and the lowest value of RPE was 6.52 downstream of the Miho stream. Full estrogen agonistic activities were observed downstream of the Kumho river and upstream of the Kum river. The partial agonistic activity was observed in upstream of the Kumho river, downstream of the Mankyung river, and upstream of the Miho stream, and no agonistic action was observed downstream of the Kum river or Miho stream, or upstream of the Mankyung river. The total estrogenic activity in the river water and sediment samples was between 0.50 pg/L and 7.4 ng/L, 3.39 pg/g and 10.70 pg/g.

Estrogenic activity of chemicals for dental and similar use in vitro

The estrogenic activities of chemicals for dental and similar use were tested by a reporter gene assay (yeast two-hybrid system) and an estrogen/estrogen receptor (ER-alpha) competition binding assay (fluorescence polarization system). Among the 10 chemicals [bisphenol-A (BPA), bis-2-hydroxypropyl methacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), dibutyl phthalate (DBP), n-butyl benzyl phthalate (BBP), n-butyl phthalyl n-butyl glycolate (BPBG), di-2-ethylhexyl phthalate (DEHP), and di-2-ethylhexyl adipate (DOA)], which were diluted with DMSO to concentrations ranging from 5 x 10(-7) to 5 x 10(-3) M, and 17beta-estradiol (E2) as a positive control, BPA and BBP showed estrogenic activity in these two assays, while the remaining eight chemicals did not at the concentrations tested. Additional data, together with in vivo and epidemiological examinations, are required. Such investigations should also provide information on the validity of these methods for testing the estrogenic activity of chemicals.

Reproductive malformation of the male offspring following maternal exposure to estrogenic chemicals

Recently, significant concerns have been placed on the widespread use of chemicals with persistent estrogenic activity for their long-term effects on human health. In this communication, we investigated whether fetal exposure to some of these chemicals at doses consumed by people, has any long-term effect on the reproductive functions of the male offspring. Thus, time-pregnant CD-1 mice were fed diethylstilbestrol (DES), bisphenol A (BPA), and aroclor (aroclor 1016) at an average concentration of 100 ng/kg/day, 50 microg/kg/day, and 50 microg/kg/day, respectively, during Days 16-18 of gestation. A high dose of DES (200 microg/kg/day) was also tested to compare the results of the current study with those of others using the high dose only. The offspring were examined at Day 3, Day 21, and Day 60 following birth. We demonstrated that BPA, aroclor, and the lower dose of DES enhanced anogenital distance, increased prostate size, and decreased epididymal weight. No effect was found on the testicular weight or size. The chemicals also permanently increased androgen receptor (AR) binding activity of the prostate at this dosage. This is the first demonstration that environmental chemicals program AR function permanently at the dosage consumed by the general population. The higher dosage of DES, on the other hand, produced an opposite effect, decreasing prostate weight, prostate AR binding, and anogenital distance, thus confirming the previous reports. To investigate whether the above mentioned effects of the chemicals represent direct or indirect effects, we also tested the effect of the chemicals on prostate development in vitro. Thus fetal urogenital sinus (UGS), isolated at the 17th day of gestation was cultured with the chemicals in the presence and absence of testosterone (10 ng/ml) for 6 days, and prostate growth was monitored by determining the size and branching of the specimen following histology. Results showed that these chemicals induced prostate growth in the presence and absence of testosterone. They also increased androgen-binding activity. Thus, the results of the in vivo studies were reproduced in the in vitro experiments, suggesting a direct effect of these chemicals on the development of fetal reproductive organs. This is the first demonstration that estrogenic chemicals induce reproductive malformation by direct interference with the fetal reproductive organs and not by interfering with the maternal or fetal endocrine system. The chemicals are able to induce malformation even in the absence of fetal testosterone; however, they are more effective in the presence of testosterone.

Determination of bisphenol A and related aromatic compounds released from bis-GMA-based composites and sealants by high performance liquid chromatography

Most of the composites and sealants used in dentistry are based on bisphenol A diglycidylether methacrylate (Bis-GMA). Reports revealed that in situ polymerization is not complete and that free monomers can be detected by different analytic methods. Concerns about the estrogenicity of bisphenol A (BPA) and other aromatic components leached from commercial products have been expressed. We studied biphenolic components eluted from seven composites and one sealant before and after in vitro polymerization using HPLC and gas chromatography/mass spectrometry and we investigated how pH modifications affect the leaching of these components. We found BPA (maximal amount 1.8 microg/mg dental material), its dimethacrylate derivative (Bis-DMA, 1.15 microg/mg), bisphenol A diglycidylether (6. 1 microg/mg), Bis-GMA (2.0 microg/mg), and ethoxylate and propoxylate of bisphenol A in media in which samples of different commercial products were maintained under controlled pH and temperature conditions. Our results confirm the leaching of estrogenic monomers into the environment by Bis-GMA-based composites and sealants in concentrations at which biologic effects have been demonstrated in in vivo experimental models. The main issue with implications for patient care and dentist responsibility is to further determine the clinical relevance of this estrogenic exposure.

Interactions of nitromusk parent compounds and their amino-metabolites with the estrogen receptors of rainbow trout (Oncorhynchus mykiss) and the South African clawed frog (Xenopus laevis)

Nitromusks, musk xylene (MX), musk ketone (MK) and musk moskene (MM) are synthetic fragrances. 4-Amino-MX (4X), 2-amino-MX (2X) and 2-amino-MK (2K) are nitromusk metabolites formed during the sewage treatment process and have been detected in effluent and surface water at concentrations four to 40 times higher than their parent compounds. To date, data to the aquatic toxicity of nitromusk compounds are limited to the parent compounds and the determination of acute and subacute effects in aquatic organisms. No data are available regarding the potential endocrine modulating effects of these compounds and/or their metabolites in aquatic organisms. Therefore, the competitive binding capability of nitromusks and their metabolites to the estrogen receptors (ER) in rainbow trout and xenopus was investigated. No binding of MX, MK and MM to the ER of either species was observed. In contrast, binding to the ER was observed for 4X, 2X and 2K in both species. The IC50 (competitive binding at the ER) of 2X in rainbow trout was 1.3 +/- 1.1 mM. In contrast, 4X, 2X and 2K bound to the xenopus ER with an IC50 of 30.8 +/- 28.5, 12.9 +/- 10.3 and 70.1 +/- 88.3 microM, respectively.

Estrogenic potential of certain pyrethroid compounds in the MCF-7 human breast carcinoma cell line

Estrogens, whether natural or synthetic, clearly influence reproductive development, senescence, and carcinogenesis. Pyrethroid insecticides are now the most widely used agents for indoor pest control, providing potential for human exposure. Using the MCF-7 human breast carcinoma cell line, we studied the estrogenic potential of several synthetic pyrethroid compounds in vitro using pS2 mRNA levels as the end point. We tested sumithrin, fenvalerate, d-trans allethrin, and permethrin. Nanomolar concentrations of either sumithrin or fenvalerate were sufficient to increase pS2 expression slightly above basal levels. At micromolar concentrations, these two pyrethroid compounds induced pS2 expression to levels comparable to those elicited by 10 nM 17ss-estradiol (fivefold). The estrogenic activity of sumithrin was abolished with co-treatment with an antiestrogen (ICI 164,384), whereas estrogenic activity of fenvalerate was not significantly diminished with antiestrogen co-treatment. In addition, both sumithrin and fenvalerate were able to induce cell proliferation of MCF-7 cells in a dose-response fashion. Neither permethrin nor d-trans allethrin affected pS2 expression. Permethrin had a noticeable effect on cell proliferation at 100 microM, whereas d-trans allethrin slightly induced MCF-7 cell proliferation at 10 microM, but was toxic at higher concentrations. Overall, our studies imply that each pyrethroid compound is unique in its ability to influence several cellular pathways. These findings suggest that pyrethroids should be considered to be hormone disruptors, and their potential to affect endocrine function in humans and wildlife should be investigated.

Comparison of short-term estrogenicity tests for identification of hormone-disrupting chemicals

The aim of this study was to compare results obtained by eight different short-term assays of estrogenlike actions of chemicals conducted in 10 different laboratories in five countries. Twenty chemicals were selected to represent direct-acting estrogens, compounds with estrogenic metabolites, estrogenic antagonists, and a known cytotoxic agent. Also included in the test panel were 17beta++-estradiol as a positive control and ethanol as solvent control. The test compounds were coded before distribution. Test methods included direct binding to the estrogen receptor (ER), proliferation of MCF-7 cells, transient reporter gene expression in MCF-7 cells, reporter gene expression in yeast strains stably transfected with the human ER and an estrogen-responsive reporter gene, and vitellogenin production in juvenile rainbow trout. 17beta-Estradiol, 17alpha-ethynyl estradiol, and diethylstilbestrol induced a strong estrogenic response in all test systems. Colchicine caused cytotoxicity only. Bisphenol A induced an estrogenic response in all assays. The results obtained for the remaining test compounds--tamoxifen, ICI 182.780, testosterone, bisphenol A dimethacrylate, 4-n-octylphenol, 4-n-nonylphenol, nonylphenol dodecylethoxylate, butylbenzylphthalate, dibutylphthalate, methoxychlor, o,p'-DDT, p,p'-DDE, endosulfan, chlomequat chloride, and ethanol--varied among the assays. The results demonstrate that careful standardization is necessary to obtain a reasonable degree of reproducibility. Also, similar methods vary in their sensitivity to estrogenic compounds. Thus, short-term tests are useful for screening purposes, but the methods must be further validated by additional interlaboratory and interassay comparisons to document the reliability of the methods.