Identification by Liquid Chromatography-Tandem Mass Spectrometry and Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry of the Contributor to the Thyroid Hormone Receptor Agonist Activity in Effluents from Sewage Treatment Plants.

3,3',5-Triiodothyroacetic acid (TRIAC) was identified as a major contributor to the activity of thyroid hormone receptor (TR) agonists in environmental water. TRIAC contributed 60-148% of the TR-agonist activity in effluents from sewage treatment plants (STPs). Meanwhile, the contributions of 3,5,3'-triiodothyronine (T3), 3,3',5,5'-tetraiodothyronine (T4), and analogues were <1%. TRIAC concentrations in the range of 0.30-4.2 ng/L are likely enough to cause disruption of the thyroid system in living aquatic organisms. The origin of TRIAC in the STP effluents was investigated by analyzing both STP influents and effluents. Relatively high concentrations of T3 and T4 (2.5 and 6.3 ng/L, respectively) were found only in the influents. TRIAC was identified only in the effluents. These findings suggested that T3 and T4 in STP influents were potentially converted into TRIAC during activated sludge treatment or by other means. The evaluation of TRIAC at relevant environmental concentrations by in vivo assays and an appropriate treatment to reduce the TR activity in sewage are needed.

Evaluation of human thyroid hormone receptor-antagonist activity in 691 chemical compounds using a yeast two-hybrid assay with Saccharomyces cerevisiae Y190.

The human thyroid receptor (hTR)-antagonist activities of 691 compounds were evaluated using a yeast two-hybrid assay with Saccharomyces cerevisiae Y190 introduced hTRα and coactivator. In parallel, those YTOX tests were conducted to evaluate whether those compounds affected either antagonism or toxicity. This is the first report that focuses on the hTR-antagonist activity of many chemical compounds suspected to be endocrine disruptor. In this study, 46 compounds exhibited antagonist activity at 50% of the maximum activity (IC × 50) within 11-9940 nM. In particular, 10,10-Oxybisphenoxarsine, triphenyltin fluoride, triphenyltin hydroxide, and chlorothalonil had strong hTR-antagonist activities. This knowledge gained from the present study will boost chemical regulation strategies for human and wildlife health.

Selective Recovery of Estrogenic Endocrine Disruptors from 48 Environmental Samples Using a Substrate for Activity-Specific Concentration.

hER-MIP is a molecularly imprinted polymer (MIP) that has been shown to selectively collect human estrogen receptor (hER) binding active substances. However, environmental samples contain various chemicals depending on the location and regional differences, and the hER binding activity depends on the sample type. Thus, the general applicability of hER-MIP to actual environmental samples must be elucidated. In this study, 48 environmental samples were collected and screened with hER-MIP, and a yeast assay was performed to evaluate the adsorption characteristics of the samples according to the adsorption and elution fractions. The results showed that hER-MIP collects hER binding active substances almost selectively but does not collect constitutive androstane receptor (CAR) binding active substances selectively. CAR binding activity was detected in the adsorbed fraction because several hER binding active substances also demonstrate CAR binding activity.

An acidic morpholine derivative containing glyceride from thraustochytrid, Aurantiochytrium.

A novel acidic morpholine-derivative containing glyceride (M-glyceride) was isolated from the cells of two strains of the thraustochytrid, Aurantiochytrium. The glyceride accounted for approximately 0.1 -0.4% of the lyophilized cells. The glyceride consisted of peaks I (85%) and II (15%). The structures of the intact and acetylated glycerides were elucidated by liquid chromatography-quadrupole time-of-flight chromatograph mass spectrometer (LC-Q/TOF) and NMR spectroscopy. The hydrate type of M-glyceride was detected as a minor component by LC-MS/MS. By 2D-NMR experiments, peaks I of the intact M-glyceride were elucidated as 1,2-didocosapentaenoyl-glyceryl-2'-oxy-3'-oxomorpholino propionic acid, and peak II was estimated 1,2-palmitoyldocosapentaenoyl- and/or 1,2-docosapentaenoylpalmitoyl-glyceryl-2'-oxy-3'-oxomorpholino propionic acid. The double bond position of docosapentaenoic acid was of the ω - 6 type (C22 = 5.ω - 6). The M-glyceride content varied by the cell cycle. The content was 0.4% of lyophilized cells at the mid logarithmic phase, and decreased to 0.1% at the mid stationary phase. When cells were grown in 1.0 µM M-glyceride-containing growth media, cell growth was stimulated to 110% of the control. With 0.1 µM acetyl M-glyceride, stimulation of 113% of the control was observed. Finding morpholine derivatives in biological components is rare, and 2-hydroxy-3-oxomorpholino propionic acid (auranic acid) is a novel morpholine derivative.

Avian eggshell thinning caused by transovarian exposure to o,p'-DDT: changes in histology and calcium-binding protein production in the oviduct uterus.

Reproductive disorders in birds are the most characteristic effects of DDT contamination of wildlife. Experimental exposure of avian eggs to the estrogenic substance o,p'-DDT causes abnormal development of the reproductive tract (shortening of the left oviduct and aberrant development of the right oviduct) and eggshell thinning in mature birds, but it is still not known how eggshell thinning occurs in the abnormal oviduct. To fill this information gap, we examined the histology of the uterine part of the oviduct in Japanese quail treated in ovo with o,p'-DDT or a synthetic estrogen, diethylstilbestrol (DES), and we performed immunohistochemical staining for the calcium-binding proteins CALB1, SPP1, and TRPV6. Both o,p'-DDT-treated and DES-treated quail had few, and scattered, gland cells in the left uterus, unlike vehicle controls, in which gland cells tightly occupied the lamina propria. The aberrantly developed right uterus retained all the components of the normal left uterus, but in immature form. Immunostaining for CALB1, SPP1, and TRPV6 was greatly reduced by both o,p'-DDT and DES; SPP1 and TRPV6 immunostaining patterns, in particular, differed distinctly from those in the controls. These findings suggest that CALB1, SPP1, and TRPV6 are molecular factors, decreased production of which is responsible for eggshell thinning. Our findings also could contribute to understanding of the eggshell formation mechanism in birds.

Measurement of the agonistic activities of monohydroxylated polychlorinated biphenyls at the retinoid X and retinoic acid receptors using recombinant yeast cells.

The possibility that a wide variety of polychlorinated biphenyls (PCBs) and their derivatives are present in the environment necessitates detailed evaluation of their toxicities. A number of PCBs and monohydroxylated PCBs (OH-PCBs) have been reported to have affinities for several nuclear receptors, and some of these compounds have been shown to have harmful effects in animals. In this study, we focused on the retinoid X receptor (RXR) and the retinoic acid receptor (RAR), which play critical roles in development and homeostasis. Specifically, we measured the agonistic activities of 91 OH-PCBs on these receptors by using yeast cells transfected with human RXRß or RARγ. Of the tested OH-PCBs, 20 exhibited agonistic activity on RXRß and 35 on RARγ, although their activities were lower than those of the respective endogenous ligands. Most of the OH-PCBs that showed potent activity on RXRß were tri- or tetrachlorinated compounds, whereas most of the active compounds on RARγ were di-, tri-, or tetrachlorinated compounds. The optimal position for the hydroxyl group relative to the bond linking the aromatic rings was ortho for RXRß and meta for RARγ. The activities of the OH-PCBs on RXRß depended strongly on the position of the hydroxyl group, whereas those on RARγ did not. Taken together with the results of our previous studies of compounds with effects on other nuclear receptors, these results provide critical information for further research on receptor-mediated toxicity, endocrine-disrupting effects, and structure-activity relationships.

Efficient extraction of estrogen receptor-active compounds from environmental surface water via a receptor-mimic adsorbent, a hydrophilic PEG-based molecularly imprinted polymer.

We report an efficient screening procedure for the selective detection of compounds that are actively bound to estrogen receptor (ER) from environmental water samples using a receptor-mimic adsorbent prepared by a molecularly imprinted polymer (MIP). To mimic the recognition ability of ER, we improved the typical MIP preparation procedure using a hydrophilic matrix with a polyethylene glycol (PEG)-based crosslinker and a hydrophobic monomer to imitate the hydrophobic pocket of ER. An optimized MIP prepared with methacrylic acid as an additional functional monomer and estriol (E3), an analogue of 17ß-estradiol (E2), exhibited highly selective adsorption for ER-active compounds such as E2 and E3, with significant suppression of non-specific hydrophobic adsorption. The prepared MIP was then applied to the screening of ER-active compounds in sewage samples. The fraction concentrated by the MIP was evaluated by in vitro bioassay using the yeast two-hybrid (Y2H) method and liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOFMS). Compared to an authentic adsorbent, styrene-divinylbenzene (SDB)-based resin, the fraction concentrated by the MIP had 120% ER activity in the Y2H assay, and only 25% peak volume was detected in LC-Q-TOFMS. Furthermore, a few ER-active compounds were identified only from the fraction concentrated by the MIP, although they could not be determined in the fraction concentrated by the SDB-based resin due to ion suppression along with high levels of hydrophobic compounds. These results indicated that the newly developed MIP effectively captured ER-active compounds and while allowing most non-ER-active compounds to pass through.

Development and validation of a simulation method, PeCHREM, for evaluating spatio-temporal concentration changes of paddy herbicides in rivers.

In pesticide risk management in Japan, predicted environmental concentrations are estimated by a tiered approach, and the Ministry of the Environment also performs field surveys to confirm the maximum concentrations of pesticides with risk concerns. To contribute to more efficient and effective field surveys, we developed the Pesticide Chemicals High Resolution Estimation Method (PeCHREM) for estimating spatially and temporally variable emissions of various paddy herbicides from paddy fields to the environment. We used PeCHREM and the G-CIEMS multimedia environmental fate model to predict day-to-day environmental concentration changes of 25 herbicides throughout Japan. To validate the PeCHREM/G-CIEMS model, we also conducted a field survey, in which river waters were sampled at least once every two weeks at seven sites in six prefectures from April to July 2009. In 20 of 139 sampling site-herbicide combinations in which herbicides were detected in at least three samples, all observed concentrations differed from the corresponding prediction by less than one order of magnitude. We also compared peak concentrations and the dates on which the concentrations reached peak values (peak dates) between predictions and observations. The peak concentration differences between predictions and observations were less than one order of magnitude in 66% of the 166 sampling site-herbicide combinations in which herbicide was detected in river water. The observed and predicted peak dates differed by less than two weeks in 79% of these 166 combinations. These results confirm that the PeCHREM/G-CIEMS model can improve the efficiency and effectiveness of surveys by predicting the peak concentrations and peak dates of various herbicides.

Agonistic effects of diverse xenobiotics on the constitutive androstane receptor as detected in a recombinant yeast-cell assay.

The constitutive androstane receptor (CAR) is a nuclear receptor and transcription factor regulating proteins involved in xenobiotic metabolism. Agonist activation of the CAR can trigger metabolic activation and toxification as well as detoxification and clearance; accordingly, xenobiotic substances acting as CAR ligands may pose a threat to human and animal health. We used yeast cells transduced with the human CAR and the response pathway to measure the CAR-agonistic activities of 549 synthetic or natural compounds: 216 of the tested compounds exhibited CAR-agonistic effects. Eighty-four percent of CAR-activating compounds were aromatic compounds, and >65% of these active compounds were aromatic hydrocarbons, bisphenols, monoalkyl phenols, phthalates, styrene dimers, diphenyl ethers, organochlorines, and organophosphates. The ten most potent compounds were 4-tert-octylphenol (4tOP; reference substance), 4-nonylphenol, diethylstilbestrol, benzyl n-butyl phthalate, 2-(4-hydroxyphenyl)-2,4,4-trimethylchroman, o,p'-DDT, methoxychlor, di-n-propyl phthalate, hexestrol, and octachlorostyrene. The activities of these nine non-reference compounds exceeded 10% of the 4tOP activity. Analysis of para-monoalkyl phenols suggests that branching of the alkyl group and chlorination at the ortho position raises potency. This study provides critical information for identifying the potential of CAR-mediated toxic hazards and for understanding the relevant mechanism.

Screening data for the endocrine disrupting activities of 583 chemicals using the yeast two-hybrid assay.

We screened 583 chemicals for receptor binding activity to the human estrogen receptor (hER), the Japanese medaka estrogen receptor (medER), and the aryl hydrocarbon receptor (AhR) using the yeast two-hybrid assay. The substances tested included substances that could potentially be produced unintentionally by industrial processes, such as halogenated steroids and phenols. Antagonistic effects on hER and the androgen receptor were also screened. The test chemicals were selected for screening on the basis of chemical structure associated with possible estrogen receptor binding activity. The current study presents the report on the screening of 583 chemicals for different kinds of endocrine disrupting activity.

Detection and measurement of the agonistic activities of PCBs and mono-hydroxylated PCBs to the constitutive androstane receptor using a recombinant yeast assay.

Polychlorinated biphenyls (PCBs) are thought to exert their toxicities mainly by binding to the aryl hydrocarbon receptor and by stimulating transcription of various genes, notably metabolizing enzymes including the cytochrome P450 (CYP) 1 family. However, PCBs and their metabolites could have potential to activate other nuclear receptors and subsequent events. We focused on the constitutive androstane receptor (CAR) inducing CYP2B and measured the agonistic activity of PCBs and mono-hydroxylated PCBs (OH-PCBs) to the CAR using yeast cells transduced with the human CAR and its response pathway. Twenty-nine of 34 tested PCBs and 72 of 91 OH-PCBs exhibited CAR agonistic effects. Of 41 OH-PCBs that had the same chlorination patterns as the tested PCBs, 9 had activities more than twice those of their non-hydroxylated analogs. In particular, 2',4',6'-trichlorobiphenyl-4-ol and 2,2',4',6'-tetrachlorobiphenyl-4-ol were 332- and 22-fold more potent than their analogs and were 15 times and 2.8 times, respectively, as active as a reference substance, 4-tert-octylphenol. The activities of 17 of the OH-PCBs were reduced to less than half those of their non-hydroxylated analogs. Four OH-PCBs derived from 3 active PCBs were inactive. However, a consistent relationship between hydroxyl substituent position and activity could not be discerned. Comprehensive evaluation of the toxic potential of PCBs and their hydroxylated metabolites and their concentrations in the environment are required.

Combining Passive Sampling with Recombinant Receptor-Reporter Gene Bioassays to Assess the Receptor Activity of Victorian Rivers.

This pilot study was initiated to provide new information on the 'hormonal' activity of Victorian rivers. Chemcatcher™ passive sampler systems containing Empore™ C18FF disks were deployed at eight riverine sites near Melbourne. Little estrogenic activity [<0.4-1.8 ng estradiol equivalents (EQ)/disk] and no retinoic acid activity (RAR, all samples <0.8 ng trans-retinoic acid EQ/disk) was observed. Almost all sample extracts showed aryl hydrocarbon receptor activity (from <4 to 29 ng ß-naphthoflavone EQ/disk). Overall, the disk extracts were eminently compatible with the bioassay screening technology, enabling the relative levels of 'hormonal activity' to be observed in the surface waters in and around Melbourne. From a practical perspective, the in situ sampling and pre-concentration provided by passive sampling reduces the manual handling risks associated with sample transport, and the number of laboratory operations required to obtain assay-ready solutions for analysis.

Evaluation of sensitizers found in wastewater from paper recycling areas, and their activation of the aryl hydrocarbon receptor in vitro.

The in vitro potential of sensitizers and related compounds (SRCs) originating from impurities in waste paper in activating the human aryl hydrocarbon receptor (AhR) α was assessed using yeast reporter gene as well as cytochrome P450 (CYP)1A1 and ethoxyresorufin O-deethylase (EROD) assays. In the yeast assay, eight compounds exhibited agonist activity, and their activity relative to ß-naphthoflavone (BNF) ranged from 1.4 × 10(-4) to 8.3 × 10(-2), with the highest activity observed for benzyl 2-naphthyl ether (BNE). In the EROD assay, six compounds caused a more significant induction of CYP1A-dependent activity than did the vehicle control at 50 µM (p<0.01), and their induction levels were 5.1- to 11-fold more potent; 1,2-bis(3-methylphenoxy)ethane (BME) was the most effective inducer. The water from the waste paper recycling area was fractioned using solid-phase extraction (SPE) combined with a C18 disk and florisil cartridge. In gas chromatography-mass spectrometry (GC-MS) analysis, SRCs were detected in the first fraction, at a total concentration of 5.5 µg/L. This fraction also activated AhR, and its activity, expressed as a BNF equivalent value, was 0.42 nM in the yeast assay. The contribution ratio of active compounds accounted for up to 34% and 4.4% observed activity of the fraction and total samples, respectively. To our knowledge, this is the first study to show that paper industry-related compounds, namely aromatic sensitizers, activate AhR by using a yeast assay and HepG2 cells.

Benchmarking organic micropollutants in wastewater, recycled water and drinking water with in vitro bioassays.

Thousands of organic micropollutants and their transformation products occur in water. Although often present at low concentrations, individual compounds contribute to mixture effects. Cell-based bioassays that target health-relevant biological endpoints may therefore complement chemical analysis for water quality assessment. The objective of this study was to evaluate cell-based bioassays for their suitability to benchmark water quality and to assess efficacy of water treatment processes. The selected bioassays cover relevant steps in the toxicity pathways including induction of xenobiotic metabolism, specific and reactive modes of toxic action, activation of adaptive stress response pathways and system responses. Twenty laboratories applied 103 unique in vitro bioassays to a common set of 10 water samples collected in Australia, including wastewater treatment plant effluent, two types of recycled water (reverse osmosis and ozonation/activated carbon filtration), stormwater, surface water, and drinking water. Sixty-five bioassays (63%) showed positive results in at least one sample, typically in wastewater treatment plant effluent, and only five (5%) were positive in the control (ultrapure water). Each water type had a characteristic bioanalytical profile with particular groups of toxicity pathways either consistently responsive or not responsive across test systems. The most responsive health-relevant endpoints were related to xenobiotic metabolism (pregnane X and aryl hydrocarbon receptors), hormone-mediated modes of action (mainly related to the estrogen, glucocorticoid, and antiandrogen activities), reactive modes of action (genotoxicity) and adaptive stress response pathway (oxidative stress response). This study has demonstrated that selected cell-based bioassays are suitable to benchmark water quality and it is recommended to use a purpose-tailored panel of bioassays for routine monitoring.

Effects of transovarian exposure to p,p'-DDT and p,p'-DDE on avian reproduction using Japanese quails.

In the 1950s to 1970s developed countries reported declines in populations of raptorial and fish-eating birds and dichlorodiphenyltrichloroethane (DDT) and its metabolites were considered causative substances because they accumulated significantly in the tissues of wild birds and animals. However, except for the estrogenic effects of o,p'-DDT, a minor component of commercial DDT, there has been no compelling evidence that DDT directly affects avian reproductive systems. To assess the possible impact of DDT on development and reproduction of birds, exposure experiments to the major component of commercial DDT, p,p'-DDT, and its persistent metabolite, p,p'-dichlorodiphenyldichloroethylene (DDE), were performed using Japanese quail (Coturnix japonica) eggs; the test substances (3 to 100 µg/g) were injected into the yolk prior to incubation, and hatched chicks were raised to adulthood. p,p'-DDT had no significant effects on the morphology and function of the reproductive systems, although the hatchability of treated eggs was reduced at the highest dose (100 µg/g). High doses of p,p'-DDE slightly enhanced the eggshell forming ability of female quails; eggshell mass and thickness were increased at 30 µg/g or more although no morphological changes were observed in the oviduct. Transcriptions of the CYP11A1 gene in the ovaries, and of AHR and ARNT in the livers, of adult females were significantly increased at 3 µg/g or more of p,p'-DDT. Except for low hatchability, transovarian exposure to p,p'-DDT or p,p'-DDE did not markedly impair the avian reproductive systems, but the hormonal actions of these compounds are likely to change reproductive and hepatic functions even after maturation.

Characteristics of the transformation frequency at the tumor promotion stage of airborne particulate and gaseous matter at ten sites in Japan.

We used a high-volume air sampler in the summer of 2007 and the winter of 2008 at ten Japanese sites (Sapporo, Sendai, Maebashi, Tsukuba, Shinjuku, Sagamihara, Shizuoka, Touhaku, Kitakyushu, and Kagoshima) to collect total suspended particulate (TSP) and gaseous matter for evaluation. We evaluated the transformation frequency at the tumor promotion stage of these samples in a cell transformation assay using Bhas 42 cells, which were established from BALB/c 3T3 cells transfected with the v-Ha-ras oncogene. All samples collected from the gaseous matter were negative for transformed foci. There were several patterns of transformation frequency at the tumor promotion stage by area for the TSP samples. At Sapporo, the transformation frequency at the tumor promotion stage was remarkably higher in winter than in summer as well as in winter at the other sites. At six urban cities from Sendai to Shizuoka, the levels of transformed frequencies per µg of suspended particulates in winter were almost the same, and were higher than those of the remaining three sites. At three sites, Touhaku, Kitakyushu and Kagoshima, the transformation results in winter were judged as negative. The characteristics of the transformed frequencies of the compounds adsorbed on particulate matter at the sampling sites were significant in winter. We also studied the correlation between the transformation frequency at the tumor promotion stage of the TSP samples and the results of quantitative analysis of 16 polyaromatic hydrocarbons (PAHs) at the ten sites. We found that the transformation frequency at the tumor promotion stage of airborne samples could not be predicted based on the quantitative results of the PAHs in those samples. These data suggest that direct risk assessment of air samples with a bioassay is more valuable than quantitative analysis of compounds such as PAHs for predicting carcinogenicity.

Screening for potential effects of endocrine-disrupting chemicals in peri-urban creeks and rivers in Melbourne, Australia using mosquitofish and recombinant receptor-reporter gene assays.

Sexually mature male mosquitofish (Gambusia holbrooki) were collected from various sites around Melbourne in 2009 to evaluate the performance of gonopodial indices as a biomarker for endocrine disruption in Melbourne's waterways. The mosquitofish indices assessed were body length (BL), gonopodial length (GL)/BL ratio, ray 4:6 ratio and the absence or presence of hooks and serrae, and these varied between sites. The study was complemented by measurements of estrogenic, retinoid, thyroid and aryl hydrocarbon (AhR) receptor activities of the water. Male mosquitofish were 16.3-21.5 mm in length, and although there was a statistically significant positive relationship showing that bigger fish had longer gonopodia than small fish (r2 = 0.52, p < 0.001), there were few significant differences in GL/BL ratio of fish between sites. Measured estrogenic activity was mostly in the range 0.1-1.7 ng/L EEQ, with one site having much higher levels (~12 ng/L EEQ). Aryl hydrocarbon (AhR) receptor activity was observed in all water samples (7-180 ng/L ßNF EQ), although there was no consistent pattern in the level of AhR activity observed, i.e., 'clean' sites were as likely to return a high AhR activity response as urban or wastewater treatment plant (WWTP)-impacted sites. There was no correlation between measurements of receptor actvity and gonopodial length (GL):BL ratio and BL. We conclude that the mosquitofish gonopodia only fulfills part of the criteria for biomarker selection for screening. The mosquitofish indices assessed were cheap and easy-to-perform procedures; however, there is no baseline data from the selected sites to evaluate whether differences in the morpholical indices observed at a site were a result of natural selection in the population or due to estrogenic exposure.

A pilot survey of 39 Victorian WWTP effluents using a high speed luminescent umu test in conjunction with a novel GC-MS-database technique for automatic identification of micropollutants.

In 2007, samples of treated effluent were collected at point of discharge to the environment from 39 wastewater treatment plants (WWTPs) located across Victoria, Australia grouped by treatment type. Sample genotoxicity was assessed with a high-throughput luminescent umu test method using Salmonella typhimurium TL210 strain, with and without addition of a commercially available metabolic activation system. Samples were also screened using a gas chromatographic-mass spectrometric mass-structure database recognition method. A genotoxic response was observed in half of the samples tested without metabolic activation system (

A pilot study of the water quality of the Yarra River, Victoria, Australia, using in vitro techniques.

A pilot study was initiated to provide the first information on the recombinant receptor-reporter gene bioassay (hormonal) activity of freshwaters in Victoria. The project involved the collection of water samples from six stations on the main stem of the Yarra River in and upstream of the city of Melbourne, Australia in April 2008 and April 2009. Samples were prepared for measurement of sample toxicity using a modified photobacterium test, genotoxicity using a high-throughput luminescent umu test method, and human and medaka estrogen receptor (hERα and medERα), retinoic acid receptor (RAR), aryl hydrocarbon receptor (AhR) and thyroid receptor (TR) assay activity using the relevant yeast-based bioassays. Most samples were only weakly or moderately toxic, with no relationship observed to location along the river. The data for 2008 suggests that at that time the Yarra River samples contained few compounds that were, in and of themselves, genotoxic. No estrogenic or thyroid, and <1 ng/L retinoic acid receptor activity was observed. AhR activity increased with progressed downstream. AhR activity was higher in April 2009 than at the same time in 2008, perhaps as a result of extensive bush fires in the catchment in the months immediately prior to sampling. About 24% of the total AhR activity observed was associated with suspended solids.

The feasibility of using mosquitofish (Gambusia affinis) for detecting endocrine-disrupting chemicals in the freshwater environment.

We evaluated the utility of gene-transcriptional responses in the liver of mosquitofish (Gambusia affinis), a species introduced to many countries and therefore widely available, for detecting endocrine-disrupting activity in water. Exposure to ß-naphthoflavone, an aryl hydrocarbon receptor (AhR) agonist, significantly increased the transcript of the cytochrome P4501A gene (cyp1a), peaking at 24 h, in both sexes at concentrations of 10 µg/L or more. 17ß-Estradiol (E(2) ) at 500 ng/L increased the number of males showing gene transcription of precursors of yolk protein, vitellogenin (Vtga, Vtgb, and Vtgc), at 24, 48, and 72 h. Exposure for 48 h to bisphenol A (BPA), an estrogen mimic, also increased vtg-positive males at 1 mg/L or more. Leachate from a Japanese stable-type landfill significantly increased vtg-positive males after 48 h exposure, and the in vitro activity of the leachate against the estrogen receptor (ER) was estimated as an E(2) equivalent of 240 ng/L by yeast transfected with the ER. Chemical analysis showed that major contributors to the ER activation were BPA and 4-tert-octylphenol. This leachate and drainage water from a control-type landfill had AhR activities, estimated by yeast with the AhR, but had no significant effect on cyp1a transcription. These results showed that mosquitofish are suitable for detecting in vivo AhR and ER effects, but are insensitive to E(2).