Exposure to Dichlorodiphenyldichloroethylene (DDE) and Metallothionein Levels in Rats Fed with Normocaloric or High-Fat Diet: A Review.

The growing number of studies on metallothioneins (MTs), cysteine-rich metal-binding proteins, have been disclosing new functions of these proteins. Thanks to their inducibility, they were considered to play a pivotal role in regulating trace metals homeostasis and in detoxification from heavy metals; nowadays, it is known that they are involved in various physiological and pathological processes, such as regulation of apoptosis, elimination of free radicals, and protection of nucleic acids against toxic insults. MT induction has been demonstrated following stress factors other than heavy metals, such as endocrine-disrupting chemicals, insecticides, and herbicides. However, retrieved data are often controversial: in some cases, xenobiotics elicit MT expression and synthesis; under different conditions, they lead to a decrease in cellular MT content. This review describes the MT response to dichlorodiphenyltrichloroethane (DDT) contamination in mammalian tissues. In particular, attention focuses on changes in MT expression, synthesis, and localization in rat liver, kidneys, and testes following oral administration of dichlorodiphenyldichloroethylene (DDE), the main metabolite of DDT, under normal dietary conditions or in combination with a high fat diet potentially able to increase the cellular uptake of this lipophilic pesticide. The potential connection between MT expression and synthesis, lipophilic substances and trace metals availability is also discussed.

Metabolic Impairments Caused by a "Chemical Cocktail" of DDE and Selenium in Mice Using Direct Infusion Triple Quadrupole Time-of-Flight and Gas Chromatography-Mass Spectrometry.

Among organic contaminants, pesticides are one of the most important groups of chemicals due to their persistent character and toxicity. However, the biological systems are exposed to a complex environment in which the contaminants can interact in a synergistic/antagonistic fashion, and for this reason, the study of "chemical cocktails" is of great interest to fully understand the final biological effect. In this way, selenium is known for its antagonistic action against several toxicants. In this paper, metabolic impairments caused by the joint exposure of p,p'-dichloro diphenyl trichloroethane (DDE) and selenium (Se) have been issued for the first time. A metabolomic workflow was applied to mice fed DDE and DDE with Se diet, on the basis of the complementary use of two organic mass spectrometric techniques, combining direct infusion mass spectrometry (DI-ESI-QqQ-TOF MS) and gas chromatography-mass spectrometry (GC-MS). The results show a good classification between the studied groups caused by about 70 altered metabolites in the liver, kidney, or brain, including the pathways of energy metabolism, degradation of phospholipidic membrane, ß-oxidation, and oxidative stress, which confirm the potential of combined metabolomic platforms in environmental studies.

Adipose tissue dysfunction as a central mechanism leading to dysmetabolic obesity triggered by chronic exposure to p,p'-DDE.

Endocrine-disrupting chemicals such as p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), are bioaccumulated in the adipose tissue (AT) and have been implicated in the obesity and diabetes epidemic. Thus, it is hypothesized that p,p'-DDE exposure could aggravate the harm of an obesogenic context. We explored the effects of 12 weeks exposure in male Wistar rats' metabolism and AT biology, assessing a range of metabolic, biochemical and histological parameters. p,p'-DDE -treatment exacerbated several of the metabolic syndrome-accompanying features induced by high-fat diet (HF), such as dyslipidaemia, glucose intolerance and hypertension. A transcriptome analysis comparing mesenteric visceral AT (vAT) of HF and HF/DDE groups revealed a decrease in expression of nervous system and tissue development-related genes, with special relevance for the neuropeptide galanin that also revealed DNA methylation changes at its promoter region. Additionally, we observed an increase in transcription of dipeptidylpeptidase 4, as well as a plasmatic increase of the pro-inflammatory cytokine IL-1ß. Our results suggest that p,p'-DDE impairs vAT normal function and effectively decreases the dynamic response to energy surplus. We conclude that p,p'-DDE does not merely accumulate in fat, but may contribute significantly to the development of metabolic dysfunction and inflammation. Our findings reinforce their recognition as metabolism disrupting chemicals, even in non-obesogenic contexts.

Efficacy of indoor residual spraying with dichlorodiphenyltrichloroethane against malaria in Gambian communities with high usage of long-lasting insecticidal mosquito nets: a cluster-randomised controlled trial.

BACKGROUND: Although many malaria control programmes in sub-Saharan Africa use indoor residual spraying with long-lasting insecticidal nets (LLINs), the two studies assessing the benefit of the combination of these two interventions gave conflicting results. We aimed to assess whether the addition of indoor residual spraying to LLINs provided a significantly different level of protection against clinical malaria in children or against house entry by vector mosquitoes. METHODS: In this two-arm cluster, randomised, controlled efficacy trial we randomly allocated clusters of Gambian villages using a computerised algorithm to LLINs alone (n=35) or indoor residual spraying with dichlorodiphenyltrichloroethane plus LLINs (n=35). In each cluster, 65-213 children, aged 6 months to 14 years, were surveyed at the start of the 2010 transmission season and followed in 2010 and 2011 by passive case detection for clinical malaria. Exposure to parasite transmission was assessed by collection of vector mosquitoes with both light and exit traps indoors. Primary endpoints were the incidence of clinical malaria assessed by passive case detection and number of Anopheles gambiae sensu lato mosquitoes collected per light trap per night. Intervention teams had no role in data collection and the data collection teams were not informed of the spray status of villages. The trial is registered at the ISRCTN registry, number ISRCTN01738840. FINDINGS: LLIN coverage in 2011 was 3510 (93%) of 3777 children in the indoor residual spraying plus LLIN group and 3622 (95.5%) of 3791 in the LLIN group. In 2010, 7845 children were enrolled, 7829 completed passive case detection, and 7697 (98%) had complete clinical and covariate data. In 2011, 7009 children remained in the study, 648 more were enrolled, 7657 completed passive case detection, and 7545 (98.5%) had complete data. Indoor residual spraying coverage per cluster was more than 80% for both years in the indoor residual spraying plus LLIN group. Incidence of clinical malaria was 0.047 per child-month at risk in the LLIN group and 0.044 per child-month at risk in the indoor residual spraying plus LLIN group in 2010, and 0.032 per child-month at risk in the LLIN group and 0.034 per child-month at risk in the indoor residual spraying plus LLIN group in 2011. The incident rate ratio was 1.08 (95% CI 0.80-1.46) controlling for confounders and cluster by mixed-effect negative binomial regression on all malaria attacks for both years. No significant difference was recorded in the density of vector mosquitoes caught in light traps in houses over the two transmission seasons; the mean number of A gambiae sensu lato mosquitoes per trap per night was 6.7 (4.0-10.1) in the LLIN group and 4.5 (2.4-7.4) in the indoor residual spraying plus LLIN group (p=0.281 in the random-effects linear regression model). INTERPRETATION: We identified no significant difference in clinical malaria or vector density between study groups. In this area with high LLIN coverage, moderate seasonal transmission, and susceptible vectors, indoor residual spraying did not provide additional benefit. FUNDING: UK Medical Research Council.

Exposure to p,p'-dichlorodiphenyldichloroethylene (DDE) induces fasting hyperglycemia without insulin resistance in male C57BL/6H mice.

Approximately 8.3% of the United States (U.S.) population have either diagnosed or undiagnosed diabetes mellitus. Out of all the cases of diabetes mellitus, approximately 90-95% of these cases are type 2 diabetes mellitus (T2D). Although the exact cause of T2D remains elusive, predisposing factors include age, weight, poor diet, and a sedentary lifestyle. Until recently the association between exposure to environmental contaminants and the occurrence of diabetes had been unexplored. However, recent epidemiological studies have revealed that elevated serum concentrations of certain persistent organic pollutants (POPs), especially organochlorine pesticides, are positively associated with increased prevalence of T2D and insulin resistance. The current study seeks to investigate if this association is causative or coincidental. Male C57BL/6H mice were exposed to DDE (2.0mg/kg or 0.4mg/kg) or vehicle (corn oil; 1mL/kg) for 5 days via oral gavage; fasting blood glucose, glucose tolerance, and insulin challenge tests were performed following a 7 day resting period. Exposure to DDE caused significant hyperglycemia compared to vehicle and this hyperglycemic effect persisted for up to 21 days following cessation of DDE administration. Intraperitoneal glucose tolerance tests and phosphorylation of Akt in the liver, skeletal muscle, and adipose tissue following insulin challenge were comparable between vehicle and DDE treated animals. To determine the direct effect of exposure to DDE on glucose uptake, in vitro glucose uptake assays following DDE exposure were performed in L6 myotubules and 3T3-L1 adipocytes. In summary, subacute exposure to DDE does produce fasting hyperglycemia, but this fasting hyperglycemia does not appear to be mediated by insulin resistance. Thus, the current study reveals that subacute exposure to DDE does alter systemic glucose homeostasis and may be a contributing factor to the development of hyperglycemia associated with diabetes.

Biphasic hormonal responses to the adrenocorticolytic DDT metabolite 3-methylsulfonyl-DDE in human cells.

The DDT metabolite 3-methylsulfonyl-DDE (3-MeSO(2)-DDE) has been proposed as a lead compound for an improved adrenocortical carcinoma (ACC) treatment. ACC is a rare malignant disorder with poor prognosis, and the current pharmacological therapy o,p'-DDD (mitotane) has limited efficacy and causes severe adverse effects. 3-MeSO(2)-DDE is bioactivated by cytochrome P450 (CYP) 11B1 in mice and causes formation of irreversibly bound protein adducts, reduced glucocorticoid secretion, and cell death in the adrenal cortex of several animal species. The present study was carried out to assess similarities and differences between mice and humans concerning the adrenocorticolytic effects of 3-MeSO(2)-DDE. The results support previous indications that humans are sensitive to the adrenocorticolytic actions of 3-MeSO(2)-DDE by demonstrating protein adduct formation and cytotoxicity in the human adrenocortical cell line H295R. However, neither the irreversible binding nor the cytotoxicity of 3-MeSO(2)-DDE in H295R cells was inhibited by the CYP11B1 inhibitor etomidate. We also report biphasic responses to 3-MeSO(2)-DDE in cortisol and aldosterone secretion as well as in mRNA levels of the steroidogenic genes StAR, CYP11B1 and CYP11B2. Hormone levels and mRNA levels were increased at lower concentrations of 3-MeSO(2)-DDE, while higher concentrations decreased hormone levels. These biphasic responses were not observed with o,p'-DDD or with the precursor DDT metabolite p,p'-DDE. Based on these results, 3-MeSO(2)-DDE remains a viable lead compound for drug design, although the adrenocorticolytic effects of 3-MeSO(2)-DDE in human cells seem more complex than in murine cells.

Effects of maternal exposure to di-isononylphthalate (DINP) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) on steroidogenesis in the fetal rat testis and adrenal gland.

Exposure to antiandrogens during the critical developmental window (i.e. sexual differentiation) can permanently demasculinize the male phenotype. Here we have investigated the effects of developmental exposure to di-isononylphthalate (DINP) (250 and 750 mg/kg) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) (50 and 100mg/kg) on 19.5-day-old fetal Sprague-Dawley rat testicular and adrenal steroidogenesis. Maternal exposure to DINP or p,p'-DDE on embryonic days (EDs) 13.5-17.5 did not down-regulate the activity of steroidogenesis in ED 19.5 male rat fetus. Protein expression levels of testicular and adrenal StAR, P450scc, 3beta-HSD and androgen receptor (AR) did not show any changes. However, p,p'-DDE caused clear abnormalities in the ultrastructure of steroidogenic cells in ED 19.5 rat testis and adrenal. These structural alterations can disturb the development and function of fetal testis and adrenal that may become evident later in life.

Mechanisms of p,p'-DDE-induced apoptosis in human peripheral blood mononuclear cells.

p,p'-Dichlorodiphenyldichloroethylene (DDE), the most stable metabolite of organochlorine insecticide p,p'-dichlorodiphenyltrichloroethane (DDT), has been detected in human populations living in malaria-endemic areas of México where this insecticide was used. DDE induces apoptosis in peripheral blood mononuclear cells (PMBC); however, the molecular mechanism of cell death induced by this compound is poorly understood. In the present study, PBMC isolated from healthy individuals (not exposed to DDE) were incubated in the presence of increasing concentrations of p,p'-DDE (0-80 microg/ml) over time. When PBMC were treated with low p,p'-DDE concentration (10 microg/ml) an antioxidant response and biomarkers of inflammation were induced, indicating a pro-inflammatory state. Moreover, when PBMC were treated with high p,p'-DDE concentration (80 microg/ml) several apoptotic biochemical events were triggered, such as activation of caspase-8, Bid, caspase-9 and caspase-3, as well as degradation of PARP and ubiquitination. The results described in this study show a possible inflammatory condition and the involvement of both extrinsic and intrinsic pathways in the induction of apoptosis in DDE-treated PBMC.

trans,trans-2,4-decadienal induces mitochondrial dysfunction and oxidative stress.

Lipid peroxidation produces a large number of reactive aldehydes as secondary products. We have previously shown that the reaction of cytochrome c with trans,trans-2,4-decadienal (DDE), an aldehyde generated as a product of lipid peroxidation in cell membranes, results in the formation of adducts. Mass spectrometry analysis indicated that His-33, Lys-39, Lys-72 and Lys-100 in cytochrome c were modified by DDE. In the present work, we investigated the effect of DDE on isolated rat liver mitochondria. DDE (162 microM) treatment increases the rate of mitochondrial oxygen consumption. Extensive mitochondrial swelling upon treatment with DDE (900 nM-162 microM) was observed by light scattering and transmission electron microscopy experiments. DDE-induced loss of inner mitochondrial membrane potentials, monitored by safranin O fluorescence, was also observed. Furthermore, DDE-treated mitochondria showed an increase in lipid peroxidation, as monitored by MDA formation. These results suggest that reactive aldehydes promote mitochondrial dysfunction.

Menstrual cycle characteristics in European and Inuit women exposed to persistent organochlorine pollutants.

BACKGROUND: Previous inconsistent results suggest that menstrual cycles may be disturbed by exposure to polychlorinated biphenyls (PCBs) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (DDE). METHODS: Information on menstrual cycle characteristics were obtained by questionnaires, and PCB and DDE were measured in serum samples from a total of 1494 women from Greenland, Swedish fishermen's wives, and inhabitants of Warsaw in Poland and Kharkiv in Ukraine. RESULTS: No consistent effects of PCB and DDE exposure on menstrual cycle characteristics were observed across populations. Within populations, we observed increased risks of short cycles (< or =24 days) among Swedish fishermen's wives exposed to high levels of PCB [odds ratio (OR) 2.5, confidence interval (CI) 1.2-5.1], and increased risk of long cycles (> or =32 days) among Polish women exposed to high levels of DDE (OR 3.1, CI 1.1-8.6). However, in Greenland it seemed that high levels of PCB or DDE were protective against long menstrual cycles (OR 0.7 CI 0.5-0.96 and OR 0.7 CI 0.5-0.99, respectively). CONCLUSIONS: It is unlikely that exposure to PCB and DDE is a main cause of menstrual disturbances. Genetic differences or dietary factors may be involved in the non-homogenous associations of organochlorine exposure and menstrual cycle between countries.

OECD validation of the rodent Hershberger assay using three reference chemicals; 17alpha-methyltestosterone, procymidone, and p,p'-DDE.

The rodent Hershberger assay is being validated as an in vivo test method for detecting androgenic or antiandrogenic compounds by the Organization for Economic Cooperation and Development (OECD). As part of the international validation work, we studied 17alpha-methyltestosterone for evaluating androgenic activity, and procymidone and p,p'-DDE for evaluating antiandrogenic activity. Male Sprague-Dawley rats were castrated at postnatal day 42, and only the rats that showed preputial separation were used in this study. Seven days after castration, chemicals were administered daily by gavages to groups of rats for 10 days, as recommended by OECD phase-2 protocol. Administration of 17alpha-methyltestosterone induced increases of weights of accessory sex tissues and glands in a dose-dependent manner. Administration of procymidone and p,p'-DDE produced a dose-dependent decrease of weights of accessory sex tissues and glands in the rats co-treated with testosterone propionate (0.4 mg/kg/day) subcutaneously. Our data strongly suggested that the current protocol of OECD Hershberger assay (phase-2) should be used as a reliable method for the detection of endocrine related toxicity of other chemicals.

Effects of perinatal combined exposure to 1,1-dichloro-2,2 bis (p-chlorophenyl) ethylene and tributyltin on male reproductive system.

Prenatal or early postnatal exposure to some synthetic chemicals may affect the later reproductive system of the offspring. There may also be unique responses observed due to exposure to combinations of chemicals that are not observed when the chemicals are present individually. 1,1-Dichloro-2,2 bis (p-chlorophenyl) ethylene (p,p'-DDE) is a persistent metabolite of DDT and tributyltin (TBT) compounds are used primarily as antifouling agents, as they exert biocidal actions. p,p'-DDE and TBT are ubiquitously distributed in the environment. Oral p,p'-DDE and TBT intake through marine products is demonstrated to be high in Japan. Consequently, the foetus and neonate are supposed to be exposed much more to p,p'-DDE and TBT via the maternal body. Therefore, effects of perinatal exposure to p,p'-DDE and/or TBT on the reproductive system after maturation have been investigated in rat male offspring of dams orally administered 125 ppm p,p'-DDE (approximately 10 mg/kg) and 25 ppm TBT (approximately 2 mg/kg) during the gestational and lactational period. In this study, growth retardation attributed to TBT has sustained in rat male offspring after perinatal exposure. However, perinatal exposure to p,p'-DDE and TBT failed to affect the male reproductive organs and sperm parameters in matured male offspring.

Organ-specific patterns of P450arom gene isoforms are modulated by p,p'-DDE in adult male European common frog, Rana temporaria.

The organ-specific gene expression patterns of P450arom isoforms have been studied in European common frog, Rana temporaria after exposure to DDE, using real-time PCR. Four groups of frogs were subcutaneously injected with DDE at 0.01, 0.1, 1 and 10 mg/kg body weight and one group, serving as the control was injected with pure corn oil. Brain, kidney, testis and liver P450aromA and P450aromB gene expressions were evaluated at day 14 after exposure. P450aromB data show that 0.1 and 10 mg DDE/kg doses caused 76% and 63% (testis) and 79% and 80% reductions, respectively, of mRNA levels. Brain P450aromB mRNA decreased 10% and 34%, respectively, after exposure to 0.01 and 0.1 mg DDE/kg. Thereafter, a 185% and 177% induction response of brain P450aromB was observed in the groups treated with 1 and 10 mg DDE/kg, respectively. In the kidney, 0.01, 0.1, 1 and 10 mg DDE/kg induced a 516%, 178%, 466% and 247% induction of P450aronB mRNA, respectively. P450aromA expression was not quantified in any of the organs. The relative abundance of P450aromB gene expression in different organs is in the order: kidney > brain > liver > testis. The present data suggest potential detrimental effect of organochlorine pesticides (OCs) and their metabolites on the European frog steroidogenic pathways. Given the high persistency in the environment and continued use in developing countries coupled with the tendency for global atmospheric transport, OCs and their metabolites such as DDE will remain a focus of concern both for scientific and societal reasons.

Exposure to CB-153 and p,p'-DDE and bone mineral density and bone metabolism markers in middle-aged and elderly men and women.

The incidence of osteoporotic fractures is rising in western societies, partly due to unknown reasons. Persistent organochlorine compounds (POC) have in animal studies impaired the normal bone metabolism and resulted in increased bone fragility, which might have health implications for POC-exposed human populations. The aim of the present study was to assess whether a high dietary intake of POC through fatty fish from the Baltic may result in decreased bone mineral density (BMD) or disturbances in biochemical markers of bone metabolism. From a study base of fishermen and fishermen's wives from the Swedish east coast who are considerably more POC-exposed than the general Swedish population, 196 men (median age 59 years) and 184 women (median age 62 years) participated in an examination of their forearm BMD, using dual energy x-ray absorptiometry (DXA). Further, POC exposure was assessed by analysis of lipid-adjusted serum levels of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE). Cadmium in urine (U-Cd) was also analyzed. Biochemical markers in serum of osteoblastic (osteocalcin) and osteoclastic (CrossLaps) functions were measured. Adjustment for potential confounders was made by employing multiple regression analyses. Univariate analyses showed significant negative associations between CB-153 concentrations and BMD, but after adjustment for age and body mass index, these associations did not remain. None of the POC exposure variables were associated with CrossLaps or osteocalcin. There were no significant associations between U-Cd and BMD or any of the biochemical biomarkers. In conclusion, the results did not provide any support for the hypothesis that the current exposure levels to POC constitute a hazard for impaired bone metabolism in the general Swedish population.

Effects of azinphos-methyl on cholinergic responses and general health in zebra finches (Taeniopygia guttata) after previous treatment with p,p'-DDE.

Although organochlorine (OC) pesticides were replaced with organophosphates (OPs) in the early 1970s, they continue to persist in orchard environments today. Extensive research has been conducted to determine the effects of currently used OPs on cholinesterase (ChE) activity; however, although OCs continue to be prevalent in areas of previous use, few studies have looked at the toxicity of a combination of residual OC compounds with currently used OP pesticides. The focus of our study was to determine the effects of azinphos-methyl (a common OP used in apple orchards today) on ChE activity and general health in zebra finches (Taeniopygia guttata) previously exposed to p,p'-DDE (a commonly detected metabolite of DDT). The main results of our study were as follows: (1) azinphos-methyl alone caused a dose-dependent inhibition of plasma and brain ChE activity; (2) p,p'-DDE in combination with azinphos-methyl did not change azinphos-methyl inhibition of ChE activity; and (3) there were suggestions of immunostimulation in birds dosed 1 year previously to p,p'-DDE and of anemia when p,p'-DDE was combined with azinphos-methyl; however, there was no dose-response for these parameters in birds subsequently dosed with p,p'-DDE.

Effects of perinatal combined exposure to 1,4-dichlorobenzene and 1,1-dichloro-2, 2-bis (p-chlorophenyl) ethylene (p,p'-DDE) on rat female offspring.

1,4-Dichlorobenzene (DCB) is used as an air freshener and a moth repellent and 1, 1-dichloro-2, 2-bis (p-chlorophenyl) ethylene (p,p'-DDE) is a persistent metabolite of 1, 1, 1-trichloro-2, 2-bis (p-chlorophenyl) ethane (DDT) previously used as a pesticide. DCB concentrations of residential air and oral p,p'-DDE intake via marine products are demonstrated to be higher in Japan than elsewhere. Consequently, human foetuses and neonates may be exposed to DCB and p,p'-DDE via the mother. Therefore, the combined effects of DCB and p,p'-DDE have been investigated in rat female offspring of dams after ingestion of these contaminants. No deteriorated reproductive outcomes of dams and developmental effects on female offspring were observed following oral administration of 25 ppm DCB (approximately 2 mg/kg) and/or 125 ppm p,p'-DDE (approximately 10 mg/kg) to dams. In this study, the thymus weight of female offspring was preserved by DCB at 6 weeks of age though the biological relevance remains unknown. Simultaneous administration of p,p'-DDE with DCB inhibited this phenomenon, through a mechanism still to be elucidated.

Relationship between DDE concentrations and laying sequence in eggs of two passerine species.

Passerine eggs make useful biomonitors of environmental pollutants. Among passerines, it is not known whether organochlorine contaminants in eggs within the same clutch are independent observations or follow a laying order effect. Intraclutch variation of DDE (1,1-dichloro-2,2-bis[(p-chlorophenyl)]ethylene) concentrations was studied in eggs collected from prothonotary warblers (Protonotaria citrea) and European starlings (Sturnus vulgaris) nesting on National Priority List sites in lower Alabama and central Colorado, respectively. All 209 eggs collected for this study contained detectable levels of DDE. Mean concentration of DDE across all prothonotary warbler eggs (mean 8.71 microg/g +/- 1.19, n = 20) was almost two orders of magnitude greater than mean concentrations of DDE in all starling eggs (mean 0.70 microg/g +/- 0.06, n = 189). In both species, there was a large amount of variability among individual eggs of the same clutch and no significant relationship between laying order and DDE concentration. Variation among eggs laid in the same sequential order was high and effectively masked any potential trends in laying order effect. We hypothesized that the variability was caused by the spatial heterogeneity of DDE on our study sites, the nature of egg development within a female passerine, or a combination of these factors. Investigators focusing on lipophilic contaminants should exercise caution when making inferences about contaminant concentrations in an entire clutch of passerine eggs after the collection and analysis of a single egg because our data show that DDE levels in a single egg collected for analysis do not consistently reflect DDE levels in the eggs remaining in the nest.

In utero exposure to organochlorines and age at menarche.

BACKGROUND: To examine the effect of in utero exposure to polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE) on age at menarche in offspring, we conducted a cohort study over two generations. METHODS: Female participants (and their offspring) in a Michigan angler cohort in which organochlorine levels had been determined previously were studied. Of their 213 female offspring aged 20-50 years, 151 participated in the study (71%). We retrospectively determined age at first menstrual bleeding. Based on repeated maternal serum measurements between 1973 and 1991, we extrapolated PCB and DDE serum levels at the time of pregnancy. To estimate the association between in utero PCB and DDE exposure and age at menarche, we used linear regression analyses controlling for birth date period, maternal age at delivery, birth weight, breastfeeding, education status and maternal height. RESULTS: An increase in the in utero DDE exposure of 15 micro g/l reduced age at menarche by 1 year (P = 0.04). There was no association with maternal PCB exposure. When controlling for estimated body size at menarche, the DDE association was no longer significant, based on a subsample of 102 women. CONCLUSION: The DDE effect on age at menarche encourages further research about in utero exposures. Prospective studies including the offspring's DDE level before menarche are of particular interest.

Enhanced rat Hershberger assay appears reliable for detection of not only (anti-)androgenic chemicals but also thyroid hormone modulators.

Development of an internationally recognized standard for the Hershberger assay as a screening tool to detect potential (anti-)androgenic chemicals is in progress. In the present preliminary study, we evaluated the reliability of the enhanced Hershberger assay to detect thyroid hormone modulating activity, while concentrating attention on possible confounding influence on evaluation of (anti-)androgenic activity. Castrated or testosterone propionate (TP; 0.2 or 0.25 mg/kg/day)-injected castrated male Crj:CD(SD) IGS rats (seven weeks of age) were dosed for 10 days by oral gavage with vehicle (corn oil) or the following chemicals: propylthiouracil (PTU; 2.5 mg/kg/day), a potent inhibitor of thyroid hormone synthesis, phenobarbital (PB; 125 mg/kg/day) and 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE; 100 mg/kg/day), two hepatic enzyme inducers that enhance the clearance of thyroid hormones. PTU markedly increased thyroid weights, and decreased serum T3 and T4, and increased serum TSH, also causing marked microscopic alteration of the thyroid gland. In comparison, PB and p,p'-DDE only significantly affect serum T4 and revealed some histopathological findings. The alterations appeared to be more robust in the presence of TP. Furthermore, data for p,p'-DDE demonstrated its anti-androgenic effects, whereas PTU and PB had little or no effects on the weights of androgen-related accessory glands/tissues: the ventral prostate, dorso-lateral prostate, seminal vesicles with coagulating glands, glans penis, Cowper's glands, and levator ani plus bulbocavernosus (LABC) muscles. Weight of the LABC muscles was decreased by PB treatment in TP-treated castrated rats. These findings in the present study suggests that the enhanced Hershberger assay, with evaluation of thyroid histopathology and weights, and hormone levels, appears to be reliable for screening for not only (anti-)androgenic chemicals but also thyroid hormone modulators. In order to evaluate whether the sensitivity and specificity of such a thyroid assay is great enough for routine screening purposes, future experiments including dose-response studies using lower dose levels have to be performed.