Two-generation reproduction study with para-tert-octylphenol in rats

Chemical contaminants in Brazilian drinking water: a systematic review

The goals of this research are to evaluate which chemical contaminations were detected in Brazil's drinking water reported in papers published from 2012 to 2019, to propose guideline values for emerging contaminants and assess which are the priority parameters from a health risk perspective. The methodology used was a systematic review. The chemical contaminants quantified were evaluated according to Brazilian drinking-water standards, and Guideline Values were proposed for emerging pollutants using conservative endpoints from NOAEL and LOAEL available in literature. From 1351 articles evaluated, 15 reached the research goal. Seventy-seven parameters were quantified in Brazilian drinking water from underground, surface and rainwater sources. Soil composition, mining, sewage and agricultural activities were the main sources for the seven classes framed: pesticides, metals, organic, endocrine disruptors, drugs, personal care products and illicit drugs. Twenty-two parameters are listed in the current Brazilian drinking water quality standard and 54 are not. Water was not considered appropriate to drink due to cadmium, aluminum, iron, nickel, mercury, atrazine, propionaldehyde, beryllium, acetone and 17 α-ethinyl estradiol (carcinogenic). Measures to reduce chemical contamination in drinking water need to be taken such as the expansion of sewage treatment and upgrading to tertiary treatment, and controlling and reducing the application of pesticides.

Hepatic glucuronidation of 4-tert-octylphenol in humans: inter-individual variability and responsible UDP-glucuronosyltransferase isoforms

4-tert-Octylphenol (4-tOP) is an endocrine-disrupting chemical. It is mainly metabolized into glucuronide by UDP-glucuronosyltransferase (UGT) enzymes in humans. The purpose of this study was to assess inter-individual variability in and the possible roles of UGT isoforms in hepatic 4-tOP glucuronidation in the humans. 4-tOP glucuronidation activities in the liver microsomes and recombinant UGTs of humans were assessed at broad substrate concentrations, and kinetics were analyzed. Correlation analyses between 4-tOP and diclofenac or 4-hydroxybiphenyl activities in pooled and individual human liver microsomes were also performed. Typical CL_int values were 17.8 mL/min/mg protein for the low type, 25.2 mL/min/mg protein for the medium type, and 47.7 mL/min/mg protein for the high type. Among the recombinant UGTs (13 isoforms) examined, UGT2B7 and UGT2B15 were the most active of catalyzing 4-tOP glucuronidation. Although the K _m values of UGT2B7 and UGT2B15 were similar (0.36 and 0.42 µM, respectively), the CL_int value of UGT2B7 (6.83 mL/min/mg protein) >UGT2B15 (2.35 mL/min/mg protein). Strong correlations were observed between the glucuronidation activities of 4-tOP and diclofenac (a probe for UGT2B7) or 4-hydroxybiphenyl (a probe for UGT2B15) with 0.79-0.88 of Spearman correlation coefficient (r _s) values. These findings demonstrate that 4-tOP glucuronidation in humans is mainly catalyzed by hepatic UGT2B7 and UGT2B15, and suggest that these UGT isoforms play important and characteristic roles in the detoxification of 4-tOP.

Bisphenol A, 4-tert-octylphenol, and 4-nonylphenol in the Gulf of Gdańsk (Southern Baltic)

The organic derivatives of phenol are classed as dangerous compounds, and their presence has been detected in surface water, bottom water, phytoplankton, zooplankton, and mussel as well as liver and muscle of fish from the Gulf of Gdańsk and in liver, muscle, and guano of gulls residing in the coastal zone of this basin. The greatest sources of bisphenol A (BPA), 4-tert-octylphenol (OP), and 4-nonylphenol (NP) were found to be the Vistula River and the water purification plant in Dębogórze. In living organisms, concentrations of BPA, OP, and NP ranged between the limit of quantification and several hundred ng g(-1) dry weight (dw), and the highest concentrations were found for BPA. Prolonged alimentary exposure to BPA, OP, and NP in fish and birds was indicated by liver/muscle concentration ratios generally >1. The most influential factors on BPA and alkylphenol concentrations in the tissues of fishes and gulls were mainly diet and habitat. The study confirmed possible bioaccumulation in the food web. High BPA and NP concentrations in guano (≤2,700 and ≤300 ng g(-1) dw, respectively) indicated the ability of birds to detoxify and signalled the reintroduction of these compounds to seawater. Herring, flounder, and cod from the Southern Baltic are a safe food source for human consumption because their BPA and alkylphenol contents are low.

Estrogenic endocrine-disrupting chemicals: molecular mechanisms of actions on putative human diseases

Endocrine-disrupting chemicals (EDC), including phthalates, bisphenol A (BPA), phytoestrogens such as genistein and daidzein, dichlorodiphenyltrichloroethane (DDT), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are associated with a variety of adverse health effects in organisms or progeny by altering the endocrine system. Environmental estrogens, including BPA, phthalates, and phytoestrogens, are the most extensively studied and are considered to mimic the actions of endogenous estrogen, 17β-estradiol (E2). Diverse modes of action of estrogen and estrogen receptors (ERα and ERβ) have been described, but the mode of action of estrogenic EDC is postulated to be more complex and needs to be more clearly elucidated. This review examines the adverse effects of estrogenic EDC on male or female reproductive systems and molecular mechanisms underlying EDC effects that modulate ER-mediated signaling. Mechanisms of action for estrogenic EDC may involve both ER-dependent and ER-independent pathways. Recent findings from systems toxicology of examining estrogenic EDC are also discussed.

Regulatory decisions on endocrine disrupting chemicals should be based on the principles of endocrinology

For years, scientists from various disciplines have studied the effects of endocrine disrupting chemicals (EDCs) on the health and wellbeing of humans and wildlife. Some studies have specifically focused on the effects of low doses, i.e. those in the range that are thought to be safe for humans and/or animals. Others have focused on the existence of non-monotonic dose-response curves. These concepts challenge the way that chemical risk assessment is performed for EDCs. Continued discussions have clarified exactly what controversies and challenges remain. We address several of these issues, including why the study and regulation of EDCs should incorporate endocrine principles; what level of consensus there is for low dose effects; challenges to our understanding of non-monotonicity; and whether EDCs have been demonstrated to produce adverse effects. This discussion should result in a better understanding of these issues, and allow for additional dialog on their impact on risk assessment.

In vivo models for male reproductive toxicology

In Vivo Models for Male Reproductive Toxicology (Rochelle W. Tyl, Research Triangle Institute, Research Triangle Park, North Carolina). Assessment of male reproductive function requires a specific set of evaluations of the various steps in successful mating from sperm production to copulation to fertilization to production of a viable litter. This unit outlines the measurements that are standard for determining the effects of treatment with toxicant on the reproductive capacity of male mice and rats.

Hormones and endocrine-disrupting chemicals: low-dose effects and nonmonotonic dose responses

For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of "the dose makes the poison," because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal, and epidemiology literature. We illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.

Alkylphenols in adipose tissues of Italian population

Alkylphenols (APs) and AP ethoxylated compounds (APEs) were screened in human subcutaneous adipose tissue samples from Italy. The samples were collected during bariatric surgery from 16 subjects (three men and 13 women) and a total of seven alkylphenol compounds (APs) was detected. Nonylphenol (NP) was the compound found at the highest level (mean 122 ng g⁻¹ fresh weight; range 10-266 ng g⁻¹ fw). Several nonylphenol ethoxylates (NPEOs) were found in all the sample analysed though the frequency of detection decreased with the increasing number of ethoxylic groups. NP4EO was found only in four patients ranging from trace amounts to 41.3 ng g⁻¹ fw. Total nonylphenols (NPEs) ranged between 45 and 1131 ng g⁻¹ fw, whereas the concentration of total octylphenols (OPEs) was at least 10 times lower (range 6-80 ng g⁻¹ fw). Our findings show that the average concentration of NP is about two times higher than that found in women from Southern Spain and up to three times that of people from Switzerland. Similarly, OP mean level is two times that reported in Finland and Spain populations. This is the first study that reports the presence of alkylphenols in the Italian population adipose tissue and it draws a baseline for further researches in order to depict a trend in human exposure to these compounds and to investigate possible consequences for human health.

Oral p-tert-octylphenol exposures induce minimal toxic or estrogenic effects in adult female Sprague-Dawley rats

Contamination of the environment with endocrine-disrupting chemicals (EDC) has raised concerns about potential health hazards for humans and wildlife. Human and wildlife exposure to one such ubiquitous chemical, p-tert-octylphenol (OP), are likely, due to its persistence in the environment and its presence in food, water, and items of daily use. OP is reported to bind to the estrogen receptor (ER) and alter expression of estrogen-responsive genes. Detrimental effects of OP exposures on the reproductive system have been observed in most, but not all, in vivo experiments. This study examined estrogenic effects of oral exposures of adult female rats to OP. In vitro, OP bound weakly to human ER and a co-activator protein, and accelerated proliferation of MCF-7 cells. Adult Sprague-Dawley rats were given OP by gavage daily for 35 d (25, 50, or 125 mg/kg/d). Body and organ weights and ovarian follicle populations were not significantly altered in OP-exposed adult rats, despite detectable levels of OP in reproductive organs. The estrous cycle of rats was slightly altered, but there were no significant estrogen-like changes in histomorphology or gene expression of the uterus. Prepubertal rats given 125 or 250 mg/kg OP by gavage for 3 d had reduced body weight compared to vehicle-exposed rats but failed to show any uterotrophic response, although 17alpha-ethinyl estradiol (EE, 10 microg/kg/d, ip) induced a threefold increase in uterine weight. Overall, results suggest that toxicity will occur before estrogenic effects with oral exposures to OP. Relevant environmental exposures likely pose little risk for estrogenic effects.

Nonylphenol and octylphenol in adipose tissue of women in Southern Spain

Alkylphenols (APs) and AP ethoxylates are environmental contaminants with endocrine disrupting activities in wildlife and humans. They have been largely used in industrial, agricultural, and domestic applications. Despite strong concerns about the consequences of human exposure to endocrine disrupters, little information is available on the presence in humans of compounds such as APs. The aim of the present study was to determine 4-nonylphenol (NP) and 4-octylphenol (OP) residues in adipose tissue of non-occupationally exposed women living in Southern Spain. NP was detected in 100% (n=20/20) and OP in 23.5% (n=4/20) of samples, with median levels of 57 and 4.5 ng g(-1) adipose tissue, respectively. Body mass index emerged as a determinant of exposure since it was associated with NP levels (p=0.041). Adipose tissue NP and OP levels are similar to the few data previously published in other countries. This is the first report on NP and OP levels in a population in Southern Spain. Further research is needed to determine trends in human exposure to these compounds and to investigate their consequences.

Prepubertal octylphenol exposure up-regulate BRCA1 expression, down-regulate ERalpha expression and reduce rat mammary tumorigenesis

BACKGROUND

Endogenous estrogens play an important role in the development of breast cancer. Octylphenol (OP) and genistein (GEN) are estrogen-like chemicals. Prepubertal estradiol and genistein exposure can up-regulate BRCA1 mRNA in mammary gland and reduce futuer breast cancer risk. In the present study, the effects of prepubertal exposure to high-dose OP and GEN on mammary carcinogenesis and the association with the expression of BRCA1 and ERalpha were investigated.

METHODS

Prepubertal female Sprague-Dawley rats were exposed to 20, 40, 80mg/kg OP daily from postnatal day (PND) 22-28, subsequently, the rats were given a single dose of 100mg/kg 7,12-dimethylbenz [a] anthracene (DMBA) on PND42 to induce mammary tumor.

RESULTS

The incidence of DMBA-induced mammary tumors significantly decreased when rats were treated with 40mg/kg OP. BRCA1 mRNA and protein expression were found up-regulated and ERalpha expression was down-regulated in the mammary tumor when rats were exposed to 40mg/kg octylphenol.

CONCLUSION

Exposure 40mg/kg octylphenol can reduce later breast cancer risk in prepubertal Sprague-Dawley rats, the protective effect of OP is associated with persistent up-regulation of BRCA1 and down-regulation of ERalpha in the mammary tumor.

Toxicokinetics of p-tert-octylphenol in male and female Sprague-Dawley rats after intravenous, oral, or subcutaneous exposures

This study was undertaken to characterize the toxicokinetics of p-tert-octylphenol (OP), a weak estrogenic compound, in male and female rats. Male and female Sprague-Dawley rats were given a single dose of OP either by oral gavage (50, 125 or 250 mg/kg), by intravenous (iv) injection (2, 4, or 8 mg/kg), or by subcutaneous (sc) injection (125 mg/kg). In a repeated dosing experiment, rats were given OP (oral) daily (25, 50, or 125 mg/kg) for 35 d (female) or 60 d (male). Blood and tissue samples were collected and analyzed for OP content using gas chromatography with detection by mass spectrometry. Blood OP concentrations were generally higher in female than male rats following a single oral or sc administration but were similar following a single iv injection. Tissue OP concentrations were also higher in female than male rats following oral exposure, consistent with the faster metabolism of OP observed in male rat liver microsomes. After subchronic administration, blood OP concentrations were higher at the end of exposure for female (33 d) (2.26-fold, not significant) and male (57 d) (3.47-fold) rats than single dosing but there was no change in the tissue OP concentrations. Gender differences in tissue OP concentrations may contribute, in part, to gender differences in the toxicity of OP in rats. The fact that OP was found in all reproductive tissues confirms its potential for direct endocrine-like effects.

Nonylphenol and octylphenol in human breast milk

Human milk is the most important form of nourishment for newborn children. Its consumption is strongly recommended by health authorities also for other important advantages. Unfortunately, in the last three decades a great number of investigations have shown the occurrence of several environmental contaminants in human milk, especially those with lipophilic properties. This study investigates the presence of nonylphenol, octylphenol (OP), nonylphenol monoethoxylate (NP1EO) and two octylphenol ethoxylates (OPEOs) (namely OP1EO and OP2EO), in human breast milk of Italian women. NP was the contaminant found at the highest levels with mean concentrations of 32 ng/mL, about two orders of magnitude higher than OP (0.08 ng/mL), OP1EO (0.07 ng/mL) and OP2EO (0.16 ng/mL). In the group of study a positive correlation among fish consumption and levels of NP in the milk was observed, in accordance with the evidence that seafood represents one of the most important sources of exposure to this group of contaminants in Italy. On the basis of the concentrations found in the breast milk samples, a maximum NP daily intake of 3.94 microg/kg/day can be calculated, which is close to the Tolerable Daily Intake (TDI) of 5 microg/kg body weight (bw) proposed by the Danish Institute of Safety and Toxicology. In the cases of OP no TDI is available, but its intake is at least six orders of magnitude lower than the NOAEL of 10 mg/kg/day derived from a two generation study on rats.

Histopathological effects of 4-tert-octylphenol treatment through the pregnancy period, on the pituitary, adrenal, pancreas, thyroid and parathyroid glands of offspring rats at adulthood

The present study was carried out to investigate the effects of 4-tert-octylphenol (OP) exposure at fetal period on adrenal, pituitary, thyroid+parathyroid and pancreas tissues of male and female offsprings. Pregnant rats were treated with OP (100 or 250mg/(kgday)) in vehicle (corn oil) or vehicle alone daily from day 1 to 20 of pregnancy. After birth, young rats were allowed to growth until adulthood. While there were no differences in data of organ weight between control and treatment groups, in contrast, a decrease of relative organ weights of thyroid+parathyroid and adrenal in high dose treatment group in male rats, otherwise an increase of final body weights was found in 250mg/(kgday) treatment group in all rats. Also, a lot of histopathological findings were observed in investigated tissues. The results of this study suggest that, the octylphenol which was applied in fetal period causes negative effects on the adrenal, pituitary gland, thyroid+parathyroid and pancreas in rats.

Alkylphenols and their ethoxylates in seafood from the Tyrrhenian Sea

The present study reports the results of an investigation on occurrence of octylphenols (OPs), nonylphenols (NPs) and their respective ethoxylates (with 1-6 ethoxylic group) in aquatic species of commercial interest from the Tyrrhenian Sea. Samples were collected at Livorno, Fiumicino and Salerno commercial harbors, during September-October 2003. The data obtained showed that almost all of the tested compounds were found in all the samples. NP was generally detected at the highest concentrations. Among the tested species common to the three sampling sites, mullets and seabreams generally showed high values of total alkylphenols (APs) and alkylphenol ethoxylates (APEOs) (44-55 ng g(-1) and 27-525 ng g(-1) fw), yet, the maximum concentrations were found in shrimps from Fiumicino (1255 ng g(-1) fw). On the contrary, the lowest concentrations were observed in hakes and anchovies (34-36 ng g(-1) and 6-37 ng g(-1) fw). Tuna, exhibited very high concentrations of total alkylphenolic compounds (APEs) (889 ng g(-1) fw). Seafood from Fiumicino fishing area, which is under the influence of the River Tiber, showed a degree of contamination of at least one order of magnitude higher than the other two sites. On the basis of the results of this study, the corresponding daily intakes of NPs are much lower than the TDI proposed by the Danish Environmental Agency.

Multigenerational study of the hepatic effects exerted by the consumption of nonylphenol- and 4-octylphenol-contaminated drinking water in Sprague-Dawley rats

Our multigenerational study evaluates the hepatic effects of the xenoestrogens nonylphenol (NP), and 4-octylphenol (4OP) on male and female rats when they are exposed uninterruptedly, from conception to adult age, to tap water containing 25ppm of NP or 4OP. Our results showed that these compounds did not induce any change in liver/body weight ratio (relative liver weight, RLW). In the morphological analysis we did not find evident signs of cytotoxicity. The most relevant findings were the presence of both an increase in the apoptotic index and in the percentage of binuclear hepatocytes in livers from exposed animals. Additionally, our study revealed the presence of hepatocellular glycogenosis (mainly in 4OP-exposed rats): the type of glycogen accumulated was in aggregates (gamma-glycogen), a non-functional form of glycogen. This study demonstrates that, at levels close to those described in the environment, NP and 4OP are capable of inducing a number of hepatic effects, potentially related with adaptive, and/or metabolic alterations of liver tissue.

Effects of p-nonylphenol and 4-tert-octylphenol on the anterior pituitary functions in adult ovariectomized rats

p-Nonylphenol (NP) and 4-tert-octylphenol (OP) are known to mimic the action of estrogens as endocrine disruptors. However, their acute effects on the pituitary and the hypothalamus functions in vivo have been uncertain. We therefore determined their effects on the anterior pituitary, in particular, gonadotropin secretion. Two weeks after ovariectomy, the rats were given a subcutaneous injection of 10 mg NP, 10 mg OP, 10 mg bisphenol A, 1 microg 17beta-estradiol, or sesame oil alone as control. Twenty-four hours after the treatment, the expression of progesterone receptor mRNA in the anterior pituitary and the level of luteinizing hormone (LH), follicle-stimulating hormone, and prolactin were determined. The expression of progesterone receptor mRNA in the anterior pituitary was significantly increased by either NP, OP, bisphenol A, or estradiol, but bisphenol A was less effective. The level of LH was significantly decreased by either NP or OP, but not by bisphenol A and estradiol. Only estradiol significantly increased the level of prolactin. The level of follicle-stimulating hormone was unchanged by any of the treatments. To check the effects of NP and OP on pulsatile LH secretion, blood samplings were done at 6-min intervals for 3 h. Twenty-four hours after treatment in ovariectomized adult rats, we found that the injection of NP significantly decreased the amplitude of LH pulses and the mean LH concentrations, but not the frequency of LH pulses. The injection of OP significantly decreased the mean LH concentrations without affecting the frequency and amplitude of the LH pulses. Finally, the rats given an injection of NP or sesame oil were intravenously injected with 50 ng of gonadotropin-releasing hormone (GnRH) to check whether NP affected the LH secretory responsiveness of the anterior pituitary to GnRH. We found that the responsiveness to GnRH in NP-injected rats was significantly attenuated compared to the sesame oil-injected rats. The present study suggests that NP, even with a single injection, suppresses the pulsatile LH secretion in adult ovariectomized rats, probably by affecting the anterior pituitary level.

Alkylphenols and alkylphenol ethoxylates contamination of crustaceans and fishes from the Adriatic Sea (Italy)

This paper presents the results of an investigation on the occurrence of alkylphenols (APs) and their ethoxylates (APEs) in 8 edible marine species from the Adriatic Sea and tries to estimate the corresponding intake for the Italian population. Two crustaceans, Nephrops norvegicus (Norway lobster) and Squilla mantis (spottail mantis shrimp), plus six fish species, Engraulis enchrascicolus (anchovy), Scomber scombrus (Atlantic mackerel), Merluccius merluccius (European hake), Mullus barbatus (red mullet), Solea vulgaris (common sole) and Lophius piscatorius (angler) were analyzed for their content of nonylphenol (NP), octylphenol (OP) and octylphenol polyethoxylates (OPEs). These compounds were found in all analysed samples. NP was detected at the highest concentrations: 118-399 and 9.5-1431 ng g(-1) fresh weight (fw) respectively in crustaceans and fish. OP was found at respective levels of 2.7-4.7 and 0.3-3.8 ng g(-1) fw in crustaceans and fish, whereas OPE was determined at respective concentrations of 1.2-16.8 and 0.2-21.1 ng g(-1) fw in the same species. These results, together with those from a previous study on 4 edible mollusc, allow to estimate respective daily intakes for NP, OP, and OPE of about 12, 0.1, and 0.1 microg day(-1) for an Italian adult living along the Adriatic Coast. In relation to NP and OP, these intakes are much lower than the doses associated with toxic effects in laboratory animals (9 mg kg(-1) bw for rats). Nevertheless, data of exposure from other sources to these chemicals and others with similar biological characteristics are needed.

Comparative study of estrogenic potencies of estradiol, tamoxifen, bisphenol-A and resveratrol with two in vitro bioassays

This study was undertaken to compare the sensitivity of two in vitro screening test methods and to determine the accuracy of predicted response to spiked laboratory water samples. A newly developed enzyme-linked receptor assay (ELRA) and a widely used yeast estrogen screen (YES) assay were selected to evaluate the estrogenic responses. Four natural, pharmaceutical, xenobiotic or phytobiotic chemicals: 17beta-estradiol (E2), tamoxifen, bisphenol-A and resveratrol were examined, and 17beta-E2 was used as a positive control. 17beta-E2 can strongly induce estrogenic response in both test systems, however, ELRA was found to be more sensitive to 17beta-E2 with a detection limit of 0.07 microg/l compared to 0.88 microg/l in YES assay. Similar results were obtained for bisphenol-A and resveratrol, and their estrogen potencies relative to E2 (100%) determined by ELRA were at least 5.6 times greater than produced by YES assay. ELRA was unable to distinguish the anti-estrogen tamoxifen and YES assay is also poor at distinguishing. Comparison of response to spiked laboratory water samples show that ELRA can give accurate determination to all four chemicals with recoveries among 70-120%, while YES can only give accurate determination to 17beta-E2 and bisphenol-A with recoveries among 69-112%. The comparative results provide evidence that ELRA is more suitable for rapid screening estrogenic potency of the environmental samples. Combination of ELRA and mammalian cellular assay will constitute an advantageous test to specify agonistic or antagonistic effects.

Reproductive toxicity evaluation of dietary butyl benzyl phthalate (BBP) in rats

Butyl benzyl phthalate (BBP) was administered in the diet at 0, 750, 3750, and 11,250 ppm ad libitum to 30 rats per sex per dose for two offspring generations, one litter/breeding pair/generation, through weaning of F2 litters. Adult F0 systemic toxicity and adult F1 systemic and reproductive toxicity were present at 11,250 ppm (750 mg/kg per day). At 11,250 ppm, there were reduced F1 and F2 male anogenital distance (AGD) and body weights/litter during lactation, delayed acquisition of puberty in F1 males and females, retention of nipples and areolae in F1 and F2 males, and male reproductive system malformations. At 3750 ppm (250 mg/kg per day), only reduced F1 and F2 offspring male AGD was present. There were no effects on parents or offspring at 750 ppm (50 mg/kg per day). The F1 parental systemic and reproductive toxicity no observable adverse effect level (NOAEL) was 3750 ppm. The offspring toxicity NOAEL was 3750 ppm. The offspring toxicity no observable effect level (NOEL) was 750 ppm, based on the presence of reduced AGD in F1 and F2 males at birth at 3750 ppm, but no effects on reproductive development, structures, or functions.

Absorption, bioavailability, and metabolism of para-nonylphenol in the rat

To better interpret the responses to para-nonylphenol (NP; CASRN84852-15-3) in in vivo toxicity studies, including estrogen-like activity, the bioavailability of 14C-radiolabelled NP has been determined in male and female CD rats following either single oral doses of 10 and 100 mg/kg, single i.v. doses of 10 mg/kg, or repeated daily oral doses of 10 mg/kg for up to 14 d. Up to 80% of an oral dose of NP was rapidly absorbed, the remainder being excreted unchanged in faeces. Excretion was largely complete within 24 h of dosing. Following absorption, NP was metabolised in the liver, with the majority of the metabolites excreted in bile, mainly as glucuronide conjugates. Unchanged NP was found only in bile and urine from female rats given a 100 mg/kg dose, indicating that metabolic saturation occurred. Following repeated dosing, steady state was reached within 7 d. There was no evidence of significant accumulation into tissue compartments nor of a significant change in clearance or the metabolite profiles in urine. These data suggest that the estrogen-like effects observed in toxicity studies with female rats at oral NP doses of approximately 50 mg/kg/d and greater are a result of the increased bioavailability of NP which occurs following metabolic saturation.

Estrogenic effects of phenolic compounds on glucose-6-phosphate dehydrogenase in MCF-7 cells and uterine glutathione peroxidase in rats

In this study, we tested phenolic compounds such as bisphenol A (BPA), 4-nonylphenol (NP), 4-octylphenol (OP) and 4-propylphenol (PP) by using glucose-6-phosphate dehydrogenase (G6PD) in estrogen sensitive human breast cancer cells (MCF-7 cells) and glutathione peroxidase (GPx) in female immature Sprague-Dawley (SD) rats. This study was designed to investigate whether phenolic compounds have estrogenic effects in these useful screening methods for endocrine disruptors. We chose 6 h as the incubation period for the G6PD assay through a preliminary experiment using 17beta-estradiol (E2). Above the concentration of 1 x 10(-8) M, BPA significantly increased the G6PD activity in a concentration-dependent manner, relative to the control. NP (over the concentration of 1 x 10(-9) M) also enhanced the G6PD activity by about 1.8 times that of the control. OP produced weaker effects on G6PD than NP, and showed a tendency to increase the G6PD activity. PP did not affect the G6PD activity. These results show that BPA and NP have the effect of enhancing G6PD activities in MCF-7 cells. In the in vivo GPx assay, both BPA and E2 significantly increased the uterus wet weights and dramatically enhanced uterine GPx activities in immature female rats in a dose-dependent manner. Treatment with NP (500 mg/kg/day) increased significantly both the uterine GPx activity and the uterus wet weights in immature female rats. OP (500 mg/kg/day) also caused a significant increase in uterine GPx activity, but had no effect on the uterus wet weights. This finding indicates that the change in uterine GPx activities could be a more sensitive parameter than that of uterus wet weights in immature rats. This study implies that phenolic compounds have a weak estrogenic effects.

Scientific issues associated with the validation of in vitro and in vivo methods for assessing endocrine disrupting chemicals

The assays required to assess the potential of chemicals to act as endocrine disrupting (ED) agents are either in place or are under current development. However, the validation and utilisation of these assays is currently being hampered by uncertainties regarding their purpose and required sensitivity, and uncertainties as to the intrinsic variability of the parameters being measured. This article discusses these several sources of uncertainty and the intrinsic variability of many of the key assay parameters. It is concluded that current uncertainties regarding the use of ED assays, and the extrapolation of rodent effects to humans, are due to the absence of an extensive agreed rodent control database for the developmental parameters under study, coupled to the established intrinsic variability of these parameters between strains/species of test animals and test protocols. Only when these factors are generally accepted, well studied and controlled for, will it be possible to employ ED assays with confidence and to relate assay data to effects likely to be seen in humans.

Determination of endocrine-disrupting compounds in environmental samples using gas and liquid chromatography with mass spectrometry

This paper describes certain applications for endocrine-disrupting compounds determination. LC-MS was applied using an electrospray ionization (ESI) technique in positive mode for alcohol polyethoxylates and nonylphenol and octylphenol polyethoxylates (NPEOn and OPEOn), and in negative mode for 4-nonylphenol (4-NP) and 4-octylphenol (4-OP) to determine targeted compounds in wastewater and sludge. GC-MS and GC-MS-MS were used to determine 4-NP, 4-tert.-octylphenol (4-t-OP), bisphenol A, estradiol-17beta, estriol estrone, testosterone, 17alpha-ethynylestradioL cholesterol, coprostan-3-ol, coprostan and coprostan-3-one in both surface water and wastewater after derivatization with N,O-bis(trimethyl-silyl)trifluoroacetamide (BSTFA). Extraction from the water samples was by an SPE technique, using either a copolymeric (Oasis HLB) or C18 silica sorbents, depending on the target contaminants. Extraction from the sludge samples was by a Soxtec system using methanol. Percentage recoveries for most of the selected compounds, using either a copolymeric (Oasis HLB) or C18 silica sorbents, were satisfactory (>60%). Quantification limits for the target compounds were at ppb levels in both water and sludge samples when using LC-ESI-MS in both positive and negative modes. They reached ppt levels in water when using GC-MS (in large volume injection mode) and GC-MS-MS. The results revealed 4-NP, NPEOn and AEOs in sludge samples at a concentration range of 1.3-8.5 microg/g, and NPEOn, OPEOn and other compounds, such as coprostan and bisphenol A, in surface water and/or wastewater samples at concentrations ranging from the ppt to ppb levels.

Effects of perinatal octylphenol on ultrasound vocalization, behavior and reproductive physiology in rats

A rodent diet containing paraffin wax was designed to administer the environmental estrogen octylphenol (OP) to nonpregnant, pregnant and lactating rats. The estrogenic activity of OP via this diet was first confirmed in ovariectomized adult animals: 20 mg OP/kg/day increased the mitoses in the vaginal epithelium, and 60 mg OP/kg/day stimulated mitoses in the uterine luminal epithelium. The effects on a variety of reproductive and nonreproductive parameters were then investigated in the offspring of dams fed OP (100-250 mg/kg/day during gestation and lactation). A number of modest reproductive and morphological effects observed in the offspring including decreased body weights in adults of both sexes, disrupted vaginal cyclicity and decreases in seminiferous tubule diameter and testis, kidney, spleen and ovary weights. Behavioral effects included increased sexual arousal in males, increased sexual motivation in females towards a female teaser and increased motor activity by females. Ultrasonic vocalizations by pups at Postnatal Day (PND) 7 were reduced in number and duration in both sexes. There were no effects of perinatal OP on ano-genital distance, prepuce separation, aggressive behavior or adult ultrasound vocalization. These observations confirm that the dietary intake of estrogenic amounts of OP during pregnancy and lactation can have a wide variety of effects in the offspring.

Evaluation of acute hepatotoxic effects exerted by environmental estrogens nonylphenol and 4-octylphenol in immature male rats

Nonylphenol (NP) and 4-Octylphenol (4OP) have shown estrogenic properties both in vivo and in vitro. Researchers have known for years that estrogens induce a wide number of hepatotoxic actions in rodents. In order to study the acute hepatic effects exerted by NP and 4OP on rat liver the following endpoints were evaluated: relative liver weight (RLW), morphology, cell cycle and ploidy status, monooxygenase enzymes content and levels of both, cytosolic estrogen receptor (cER) and microsomal binding sites for estrogens (mEBS). Immature male Sprague-Dawley rats were injected intraperitoneally (i.p.) with 60 mg/kg of NP or 4OP for 1, 5 or 10 days. Despite the fact that RLW of the animals was not modified but any treatment, the histopathological study revealed the presence of an increase in the percentage of both, mitotic activity and Ki-67-labeling index (LI) in the livers from animals treated with alkylphenols in absence of any degenerative lesion. Furthermore, all the livers from alkylphenols-treated groups showed the presence of abnormal mitosis and c-mitosis. Although the levels of both, cER and cytochrome P450 (Cyt. P450) were not affected by any treatment, concentration of the mEBS was decreased after 10 days of treatment with alkylphenols. These findings taken together suggest that the exposition to alkylphenols induce cell proliferation and spindle disturbances and that these compounds are capable of modulating the expression of putative membrane receptors for estrogens.

Effects of perinatal exposure to flutamide on sex hormones and androgen-dependent organs in F1 male rats

Flutamide, which has antiandrogenic properties, was administered to pregnant rats, and effects on male offspring were examined. Crj: CD (SD) IGS (SPF) females were administered flutamide (0.15, 0.6, 2.5, 10.0, 100 mg/kg, p.o.) from gestation Day 14 to post parturition Day 3. The number of pups, body weights, clinical features, anogenital distance (AGD), nipple retention, testicular descent, and urogenital malformation in F1 males were examined. Hormone measurement, necropsy and histopathological examination were carried out at post-neonatal Day 4 (PND 4) and PND 60. Sperm analysis was also carried out at PND 60. Decrease in body weight was seen in the 100 mg/kg group and the AGD was decreased at 2.5 mg/kg and above. Retention of nipples, hypospadia, vaginal pouches, penis malformation, unilateral ectopic testis, and decrease of organ weights (prostate, seminal vesicles, levator ani muscle plus bulbocavernosus muscle, testis) were observed at 10 mg/kg and above. Testicular testosterone (T) was increased significantly with 100 mg/kg at PND 4 and tendencies for increase were observed in serum T, LH and FSH at 10 mg/kg and more at the same time point. In contrast, elevated levels of LH and FSH were seen with 100 mg/kg at PND 60. Histopathological examination revealed defects or hypoplastic changes of genital organs (> or = 10 mg/kg), squamous metaplasia (10 mg/kg) or mucification (100 mg/kg) of the urethral diverticulum epithelium and inflammation of genital organs (100 mg/kg). Though only undescended testes lacked spermatogenesis at 10 mg/kg, atrophic change of seminiferous tubules and azoospermia were observed in the 100 mg/kg group, despite testicular descent. Perinatal administration of flutamide affected F1 male rats at 2.5 mg/kg and above. In addition to urogenital malformation, 100 mg/kg flutamide caused high LH and FSH levels at PND 60. This study indicates that the most sensitive parameter is AGD, whereby reduction was observed at 2.5 mg/kg. A clear no-effect level (NOEL: 0.6 mg/kg) was obtained in this perinatal study of an antiandrogenic chemical.

Effect of nonylphenol on serum testosterone levels and testicular steroidogenic enzyme activity in neonatal, pubertal, and adult rats

Previous dose range-finding studies with nonylphenol (NP) administered to rats in a soy- and alfalfa-free diet showed apparent feminization of several endpoints in male rats at doses of 25 ppm and above. One possible mechanism contributing to these effects is a reduction of testosterone at critical developmental periods. The present study was conducted as an adjunct to a multigeneration study and was designed to examine the effect of NP on testosterone production. Male rats in the F1 and F2 generations were exposed through their dams or directly to various dietary doses of NP (0, 25, 200 and 750 ppm) throughout gestation and until sacrifice at either postnatal day 2 (PND2), PND50, or PND140. Male pups in the F3 generation were examined only on PND2. At PND2, serum testosterone levels were significantly decreased in all groups exposed to NP in the F1 generation, but not in the F2 or F3 generations. The activity of 17alpha-hydroxylase/C17, 20 lyase (P450c17) in PND2 testicular homogenates was not affected by NP treatment. In F1 and F2 PND50 and PND140 rats, NP treatment did not affect serum testosterone levels. The absolute dorsolateral prostate weight was increased in the 200 and 750 ppm dose groups only in the F1 PND50 rats, however, no significant effects were observed in other male reproductive organs. NP treatment did not affect P450c17 activity in microsomes prepared from testes of F1 PND50 or PND140 rats. However, P450c17 activity was significantly decreased in testicular microsomes of F(2) PND50 (200 and 750 ppm dose groups) and PND140 (25, 200, and 750 ppm dose groups) rats. A decrease in testicular beta-nicotinamide adenine dinucleotide phosphate (NADPH) P450 reductase was also observed in all PND50 and PND140 NP-exposed rats of the F1 and F2 generations. The ability of NP to directly inhibit P450c17 activity in vitro at concentrations of 1-100 microM was also demonstrated. These results indicate that NP can inhibit the activity of enzymes involved in testosterone synthesis, but suggest minimal effects on testosterone or testosterone-dependent endpoints via this mechanism.

Neonatal low- and high-dose exposure to estradiol benzoate in the male rat: I. Effects on the prostate gland

Brief exposure of rats to high doses of natural estrogens early in life results in permanent alterations of the prostate gland, which include differentiation defects, altered gene expression, and dysplasia with aging. Whether low-dose treatments can cause similar effects in the developing prostate remains controversial. The current project was designed to determine the dose-response relationship of the prostate gland to estradiol exposure during the developmentally critical neonatal period in the rat. Male Sprague-Dawley (SD) rats were treated on Days 1, 3, and 5 of life by s.c. injections of a 7-log range of doses (0.015 microg/kg to 15.0 mg/kg) of beta-estradiol-3-benzoate (EB) in 25 microl of peanut oil (Arachis) as vehicle. In a separate block, neonatal Fisher 344 (F344) rats received 0.15, 15.0, or 1500.0 microg EB/kg. Rats were killed on Postnatal Day (PND) 35 or 90, and the prostates were microdissected, weighed, and frozen for immunohistochemistry. Preputial separation and hepatic testosterone hydroxlase activities were monitored and measured to determine the onset of puberty. On PND 35, there was an increase in prostate weights of SD rats treated with low doses of EB and a decrease in prostate weights of SD rats treated with high doses. The low-dose effect was entirely abolished by PND 90, and only high-dose suppression of organ sizes was found. The transient nature of the effect in low-dose animals suggests an advancement of puberty as the cause for increased reproductive organ weights on PND 35. F344 rats were more sensitive than SD rats to the suppressive effects of high doses of neonatal EB on PND 90. Despite this heightened responsiveness in the F344 rats, a low-dose estrogenic effect on adult prostate weights was not observed. Thus, in the rat model a sustained effect at low doses of natural estrogens is not present in the prostate glands.

Reproductive effects in male and female rats from neonatal exposure to p-octylphenol

A number of alkylphenolic compounds are used in a variety of commercial products and have been shown in in vitro studies to be weakly estrogenic, but in vivo data are not available addressing this issue in mammals. Human exposure to alkylphenols may occur not only from these environmental contaminants but also through contact with manufactured and metabolic breakdown products. In this study, Sprague-Dawley rats were exposed to octylphenol by oral gavage at doses of 0 (vehicle: corn oil), 12.5, 25, 50, or 100 mg/kg once daily on postnatal days 1 through 5 to examine its effects on male and female reproductive function after puberty. In addition, preputial separation and vaginal opening as endpoints of sexual maturation, estrous cycling, sperm count, serum testosterone concentration, and histopathologic changes of the reproductive organs of male and female rats were examined. Male reproductive organs were weighed at necropsy. Body weights of male and female rats exposed to octylphenol at 50 and 100 mg/kg throughout the study after the administration period, those of both sexes at 7 and 9 weeks of age in the 25 mg/kg group, and that of females at 9 weeks of age in the 12.5 mg/kg group were lower than those of controls. Significant delays in acquisition of puberty in males and females exposed to octylphenol at 50 and 100 mg/kg were observed. Estrous cycle, copulation and fertility, sperm count, and serum testosterone concentration were not affected by neonatal exposure to octylphenol. Significant decrease in absolute and relative prostate weight in the 12.5, 25, 50, and 100 mg/kg groups, and absolute epididymal weight in the 100 mg/kg group, increase in relative testes weight in the 100 mg/kg group, and relative seminal vesicle weights in the 50 and 100 mg/kg groups were found. Histopathologic analyses of reproductive organs in male and female rats exposed neonatally to octylphenol revealed no marked alterations. The results of this study indicate that early neonatal exposure to octylphenol by oral gavage did not cause dysfunction of reproductive performance (mating and fertility) in male or female rats, and no disruption of development of the reproductive tract was observed in male or female rats, while significant decreases in body weights in the 25 mg/kg and more groups, delays of sexual maturation in the 50 mg/kg and greater groups, and decrease in ventral prostate weights in all octylphenol-treated groups were found. Therefore, it is concluded that NOAEL (no-observed adverse effect level) for systemic toxicity was < or =12.5 mg/kg/day and that for reproductive toxicity was 100 mg/kg/day under the present experimental condition.

Differential effects of octylphenol, 17beta-estradiol, endosulfan, or bisphenol A on the steroidogenic competence of cultured adult rat Leydig cells

In the current studies, we evaluated the effects of 4-tert-octylphenol (OP), endosulfan, bisphenol A (BPA), and 17beta-estradiol on basal or hCG-stimulated testosterone formation by cultured Leydig cells from young adult male rats. Exposure of Leydig cells to increasing concentrations of OP (1 to 2000 nM), 17beta-estradiol (1 to 1000 nM), endosulfan (1 to 1000 nM) or BPA (1 to 1000 nM), alone or with 10 mIU/mL hCG for 4 or 24 h, did not lower ambient testosterone levels, although cells exposed to higher OP concentrations + hCG for 24 h often had modest declines in testosterone (10 to 20%). Of interest, exposure to the highest concentration OP (2000 nM) alone for 4 or 24 h increased testosterone levels (approximately 2-fold in 4-h exposed cells). Whether prior exposure to OP + hCG for 24 h affects the subsequent conversion of steroid substrates to testosterone over 4 h was evaluated. Progressive declines in 1 microM 22(R) hydroxycholesterol, 1 microM pregnenolone, or 1 microM progesterone conversion to testosterone was observed beginning at 100 to 500 nM OP exposure (maximal declines of 40 to 12% of controls were observed); however, the conversion of 1 microM androstenedione to testosterone was not affected by OP. These results suggested that 24-h exposure to OP + hCG has no effect on 17beta-hydroxysteroid dehydrogenase, which converts androstenedione to testosterone, but that it inhibits the 17alpha-hydroxylase/C17-20 lyase step, which converts progesterone to androstenedione. In addition, potentially, OP could inhibit cholesterol side/chain cleavage activity, which converts cholesterol to pregnenolone, and/or 3beta-hydroxysteroid dehydrogenase, which converts pregnenolone to progesterone. Of interest, exposure to increasing concentrations of 17beta-estradiol (1 to 1000 nM), endosulfan (1 to 1000 nM), or BPA (1 to 1000 nM) + hCG for 24 h had no effect on subsequent conversion of 22(R)hydroxycholesterol to testosterone. Furthermore, the inhibiting effects of OP + hCG exposure on subsequent conversion of progesterone to testosterone was unaffected by concomitant exposure to the pure estrogen antagonist, ICI 182,780, or the antioxidants, ascorbate or dimethyl sulfoxide, suggesting that the actions of OP are not mediated through binding to estrogen receptor alpha or beta or by free radical induced damage to steroidogenic enzymes, respectively. These results demonstrate that direct exposure of adult Leydig cells to OP may have subtle effects on their ability to produce testosterone, which may not be detected by measuring ambient androgen levels. In addition, the effects of OP on Leydig cell testosterone formation appear to be different from those of the native estrogen, 17beta-estradiol, and from other reported weak xenoestrogens such as endosulfan and BPA.

Alkylphenolic compounds in edible molluscs of the Adriatic Sea (Italy)

This paper reports the first group of results on alkylphenol (APE) contamination of seafood in the Adriatic Sea, in the framework of a national project on the quality of this Sea (PRISMA 2). Nonylphenol (NP), octylphenol (OP), and their ethoxylates (NPE and OPE) were detected in edible molluscs, either filter feeders or predators (clams, mussels, cuttlefishes, and squids), caught from 15 harbors along the Italian coast in the Adriatic Sea in 1997. NP was the compound found always at levels much higher than the other APEs in all the examined species. It reached the maximum concentration of 696 ng/g fresh weight in the squids from the central Adriatic Sea. OP generally occurred at levels 30 times lower than NP. OP was found up to a level of 18.6 ng/g in squids from central Adriatic Sea. OPE was the compound always spotted at the lowest concentrations, up to 0.43 ng/g. NPE was always below the detection limit. The pattern of contamination in the three areas examined was different between bivalve and cephalopod species. No exhaustive risk assessment for marine organisms and human health can be conducted on the basis of these results because data are insufficient. Yet, the occurrence of NP suggests a negligible risk for mussels, which represent the only molluscs for which data are adequate. As to the possible human health implications, the consumption of molluscs of the Adriatic Sea implies APE intakes that are some orders of magnitude lower than those responsible for toxic effects in laboratory animals. Despite these apparently low risks for mussels and human health, the reasons for concern still remain because the levels of alkylphenols found in this study indicate a general contamination of the Adriatic Sea even far from the cost. Furthermore, these levels might represent an unacceptable hazard for other marine organisms. Finally, they contribute to the general environmental estrogen pool.

Effects of neonatal exposure to a high-dose p-tert-octylphenol on the male reproductive tract in rats

Time-course alterations in morphological changes of the reproductive tract including spermatogenesis as well as pituitary and gonadal hormones, reproductive ability, and the size of the sexually dimorphic nucleus of the preoptic area (SDN-POA) were investigated in male rats neonatally exposed to 100 mg/kg p-tert-octylphenol (OP) subcutaneously. OP treatment affected hormone levels of follicle stimulating hormone (FSH) and testosterone, reproductive organ weights and sperm counts. Slightly depressed FSH levels at prepuberty and prolonged suppression of testosterone till 7 weeks of age were observed as two hormonal alterations. The lasting reduction in testosterone appeared to be associated with growth inhibition of male reproductive organs such as the testis, prostate and epididymis, these demonstrating low organ weights compared with those of age-matched controls till 7 weeks of age. The FSH concentrations after puberty showed a rise to values equal to or higher than those of the control group, suggesting recovery of maturation of the reproductive tract. No morphological abnormalities, even with morphometric stage analysis of spermatogenesis, were detected in the male reproductive tract throughout the study. Size of the SDN-POA and reproductive ability was comparable to those in controls. At the termination (18 weeks of age), however, a reduction in the sperm count in the epididymis of OP-treated animals demonstrated a possibility that the male reproductive system might be still affected by neonatal exposure to OP. The results observed demonstrate that neonatal exposure to a high-dose OP exerts estrogenic action directly or indirectly, resulting in slight but prolonged impairment of the male reproductive tract. The suppression of FSH caused by modulation of the hypothalamus-pituitary control system may be the trigger for the impairment, while the possibility of direct estrogenic action of OP is not ruled out. Our results also indicate that more sensitive endpoints should be established to detect the effects of neonatal exposure to estrogens or estrogenic compounds on the male reproductive tract.

Testing for endocrine disruption post-EDSTAC: extrapolation of low dose rodent effects to humans

The study of chemically-induced endocrine disruption in mammals is a relatively new field of endeavour, and it has been assailed by an unusual level of disagreement among investigators regarding the developmental effects produced by chemicals in animals. This article discusses the several sources of uncertainty in endocrine toxicity studies, and the intrinsic variability of many of the key experimental parameters. It is concluded that current uncertainties regarding extrapolation of rodent effects to humans are due to the absence of an extensive agreed rodent control database for the developmental parameters under study, coupled to the established intrinsic variability of these parameters between strains/species of test animals and test protocols. Only when these factors are generally accepted and well studied will it be possible to relate effects seen in rodents to humans.

Effects of 4-tert-octylphenol on initiation and maintenance of pregnancy following oral administration during early pregnancy in rats

4-tert-Octylphenol (OP) is an alkylphenol that is an intermediate in the production of alkylphenol ethoxylates. OP has been reported to be the most potent estrogenic alkylphenol in vitro. In the present study, the effects of OP on initiation and maintenance of pregnancy were investigated in rats. Inseminated female rats were orally given OP at 0,15.6,31.3,62.5 and 125 mg/kg on day 0 through day 8 of pregnancy. Female rats were sacrificed on day 20 of pregnancy, and pregnancy outcome was determined. Decreases in body weight gain and food consumption on days 0-9 were found at 31.3 mg/kg and above, and at 15.6 mg/kg and above, respectively. The pregnancy rate was not adversely affected by OP administration during early pregnancy even at 125 mg/kg. The incidence of post-implantation loss per litter at 31.3 mg/kg and above was significantly higher than that in the control group. The body weights of live fetuses in the OP-treated groups were not significantly different from those in the control group. No increase in the incidence of fetuses with external malformations was found in any OP-treated group. We concluded that OP during early pregnancy caused post-implantation embryonic loss at doses that showed maternal toxicity.

Endocrine disrupting compounds: effect of octylphenol on reproduction over three generations

With the growing concern that environmental chemicals might impair human and animal fertility, it is important to investigate the possible influence of these substances on sexual differentiation and genital development of mammals. Many of these substances are suspected to interfere with endocrine processes, and exposure during critical periods of prenatal development might affect reproductive performance over several generations. Alkylphenols and their metabolites are lipophilic substances exerting apparent estrogenic action in in vitro and in vivo testing systems. With the widespread industrial use of alkylphenols, these are disseminated in the environment with sewage sludge, and domestic animals and humans are likely to be exposed via the food chain. Using the pig as an in vivo model, we studied the effect of intrauterine exposure to tertiary octylphenol (OP) on essential reproductive parameters over 3 generations. Sows were treated daily from D 23 to 85 of pregnancy with either 0, 10 or 1000 micrograms OP/kg body weight. Treatment with OP extended pregnancy length and induced basal cell proliferation in the cervical epithelium of the parental generation. In F1 offspring of sows treated with the low dosage of OP, onset of puberty was accelerated. Furthermore, when F1 gilts and F1 boars originating from sows treated with high dosages of OP were bred, the litter size was reduced. The results of the present study are compared with previous reports on estrogenicity of OP, and the usefulness of in vivo animal or embryo models for the evaluation of possible consequences of human exposure to endocrine disrupting compounds is discussed. Furthermore, possible consequences of exposure to endocrine disrupting compounds for the embryo transfer industry are addressed.

Getting the problem of endocrine disruption into focus: the need for a pause for thought

The study of chemically-induced endocrine disruption in mammals is a relatively new field of endeavour, and it has been assailed by an unusual level of disagreement among investigators regarding the developmental effects produced by chemicals in animals. This article discusses the several sources of uncertainty in endocrine toxicity studies, and the intrinsic variability of many of the key experimental parameters. It is concluded that current uncertainties are due to the absence of an extensive agreed control database for the developmental parameters under study, coupled to the established intrinsic variability of these parameters between strains/species of test animals and test protocols. Only when these factors are generally accepted and well studied will it be possible to design studies capable of distinguishing the possible subtle endocrine toxicity of chemicals and chance observations that cannot be independently reproduced.

Reduced sperm counts in guppies (Poecilia reticulata) following exposure to low levels of tributyltin and bisphenol A

There is increasing evidence that normal male reproductive function can be disrupted by exposure to pollutants in the environment that can exogenously mimic, antagonize or block sex-hormone function. One possible consequence of exposure to these xenobiotics is disruption to spermatogenesis, but results thus far provide only indirect and inconsistent evidence. In this study we exposed adult male guppies (Poeciliidae: Teleostei) to environmentally relevant levels of the common xenobiotics tributyltin (11.2-22.3 ngl-1) and bisphenol A (274-549 micrograms l-1) in experimental aquaria. After 21 days of exposure, we found significant declines (by 40-75%) in total sperm counts for male fishes exposed to tributyltin and bisphenol A compared with controls. This short-term decline in sperm count is unlikely to be the result of endocrine-mediated alteration of the germ line, and we found no change in testis size or sperm lengths between treatments. However, Sertoli cells, which facilitate the transport of maturing sperm into the testicular deferent duct (where they are stored prior to ejaculation), are directly sensitive to xenobiotic action and it is therefore possible that spermatogenesis was inhibited through in vivo interference with normal Sertoli-cell function.

Comparative effects of neonatal exposure of male rats to potent and weak (environmental) estrogens on spermatogenesis at puberty and the relationship to adult testis size and fertility: evidence for stimulatory effects of low estrogen levels

This study investigated whether neonatal exposure of male rats to estrogenic compounds altered pubertal spermatogenesis (days 18 and 25) and whether the changes observed resulted in long-term changes in testis size, mating, or fertility (days 90-100). Rats were treated neonatally with a range of doses (0.01-10 microg) of diethylstilbestrol (DES; administered on alternate days from days 2-12), a high dose of octylphenol (OP; 2 mg administered daily from days 2-12) or bisphenol A (Bis-A; 0.5 mg administered daily from days 2-12), or vehicle, while maintained on a standard soy-containing diet. The effect on the same parameters of rearing control animals on a soy-free diet was also assessed as was the effect of administering such animals genistein (4 mg/kg/day daily from days 2-18). Testis weight, seminiferous tubule lumen formation, the germ cell apoptotic index (apoptotic/viable germ cell nuclear volume), and spermatocyte nuclear volume per unit Sertoli cell nuclear volume were used to characterize pubertal spermatogenesis. Compared with (soy-fed) controls, DES administration caused dose-dependent retardation of pubertal spermatogenesis on day 18, as evidenced by decreases in testis weight, lumen formation, and spermatocyte nuclear volume per unit Sertoli cell and elevation of the germ cell apoptotic index. However, the two lowest doses of DES (0.1 and 0.01 microg) significantly increased spermatocyte nuclear volume per unit Sertoli cell. Similarly, treatment with either OP or Bis-A significantly advanced this and some of the other aspects of pubertal spermatogenesis. Maintenance of control animals on a soy-free diet also significantly advanced lumen formation and spermatocyte nuclear volume per unit Sertoli cell compared with controls fed a soy-containing diet. Administration of genistein reversed the stimulatory effects of a soy-free diet and significantly retarded most measures of pubertal spermatogenesis. In general, plasma FSH levels in the treatment groups changed in parallel to the spermatogenic changes (reduced when pubertal spermatogenesis retarded, increased when pubertal spermatogenesis advanced). By day 25, although the changes in FSH levels largely persisted, all of the stimulatory effects on spermatogenesis seen on day 18 in the various treatment groups were no longer evident. In adulthood, testis weight was decreased dose dependently in rats treated neonatally with DES, but only the lowest dose group (0.01 microg) showed evidence of mating (3 of 6) and normal fertility (3 litters). Animals treated neonatally with OP or Bis-A had normal or increased (Bis-A) testis weights and exhibited reasonably normal mating/fertility. Animals fed a soy-free diet had significantly larger testes than controls fed a soy-containing diet, and this difference was confirmed in a much larger study of more than 24 litters, which also showed a significant decrease in plasma FSH levels and a significant increase in body weight in the males kept on a soy-free diet. Neonatal treatment with genistein did not alter adult testis weight, and although most males exhibited normal mating and fertility, a minority did not mate or were infertile. It is concluded that 1) neonatal exposure of rats to low levels of estrogens can advance the first wave of spermatogenesis at puberty, although it is unclear whether this is due to direct effects of the estrogen or to associated elevation of FSH levels; 2) the effect of high doses of OP and Bis-A on these processes is essentially benign; and 3) the presence or absence of soy or genistein in the diet has significant short-term (pubertal spermatogenesis) and long-term (body weight, testis size, FSH levels, and possibly mating) effects on males.

Subcutaneous treatment of p-tert-octylphenol exerts estrogenic activity on the female reproductive tract in normal cycling rats of two different strains

Effects of p-tert-octylphenol (OP), an endocrine disrupting chemical (EDC), on the female reproductive tract of normal cycling Fischer 344 (F344) and Donryu rats were investigated. OP was subcutaneously injected at concentrations of 12.5, 25, 50 or 100 mg/kg for 28 days. The most notable changes were the disappearance of normal cyclicity in the 50 mg/kg or more OP-treated groups of both the strains, and the appearance of persistent estrus (PE) evident on examination of vaginal smears in the 100 mg/kg groups of both the strains, the effects being time- and dose-dependent. In PE rats of both the strains, the uterine morphology deviated from the normal for each estrous stage of the cycling rats, and proliferation in the endometrium was slightly increased. The data for uterine weights, luminal epithelial cell-heights and/or numbers of epithelial cells in the endometrium demonstrated equivocal alteration. In both the strains, the serum 17beta-estradiol (E2) levels were decreased with 50 mg/kg of OP or more. Serum concentrations of the administrated chemical were dose and duration-dependently increased in all the treated groups of both the strains. The results demonstrate that subcutaneous administration of OP at doses of 50 mg/kg or more exerts time- and dose-dependent estrogenic activity on the reproductive tract of normal cycling female Donryu and F344 rats, indicating similar qualitative sensitivity to the effects in both the strains. Vaginal cytology may be the most sensitive endpoint for the detection of estrogenic activity of potential EDCs using adult cycling rats.

Irreversible effects of neonatal exposure to p-tert-octylphenol on the reproductive tract in female rats

It has been known for many years that administration of androgens or estrogens at critical periods of development in mammals causes severe long-term effects on the endocrine/genital systems. The environmental pollutant p-tert-octylphenol (OP) possesses a weak but clear estrogen agonist activity in in vitro and in vivo studies. In the present study, effects of neonatal exposure to OP on the reproductive tract of female rats were investigated. Newborn female pups were injected with 100 mg/kg OP subcutaneously within 24 h after birth. Administration was repeated every other day until postnatal day 15 (total of eight doses). Before weaning, serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) remained at low levels during OP exposure, although the serum FSH peak and the high LH level were obvious in the controls. Histologically, inhibition of uterine gland genesis was apparent. The day of vaginal opening was about 4 days earlier in OP-treated animals than in controls. Persistent estrus was consistently observed in OP-treated animals. Atrophic and polycystic ovaries without corpora lutea showed anovulation. In the endometrium, cell-proliferative activity and cell-death were increased and decreased, respectively, and expression of estrogen receptor alpha mRNA was apparent by in situ hybridization. Unexpectedly, endometrial hyperplasias appeared at 8 weeks of age. After ovariectomy, vaginal smears immediately became of castration type and the uterus was atrophied. These results suggested that neonatal exposure to a high dose of OP alters developmental hormonal secretion presumably due to a hypothalamo-pituitary-ovarian disorder, with accelerated vaginal opening, subsequent persistent estrus, and uterine endometrial hyperplasia. The changes in the uterus and vagina are ovary-dependent.

Endocrine-disrupting chemicals: prepubertal exposures and effects on sexual maturation and thyroid function in the male rat. A focus on the EDSTAC recommendations. Endocrine Disrupter Screening and Testing Advisory Committee

Puberty in mammalian species is a period of rapid interactive endocrine and morphological changes. Therefore, it is not surprising that exposure to a variety of pharmaceutical and environmental compounds has been shown to dramatically alter pubertal development. This concern was recognized by the Endocrine Disrupter Screening and Testing Advisory Committee (EDSTAC) that acknowledged the need for the development and standardization of a protocol for the assessment of the impact of endocrine-disrupting compounds (EDC) in the pubertal male and recommended inclusion of an assay of this type as an alternative test in the EDSTAC tier one screen (EPA, 98). The pubertal male protocol was designed to detect alterations of pubertal development, thyroid function, and hypothalamic-pituitary-gonadal (HPG) system peripubertal maturation. In this protocol, intact 23-day-old weanling male rats are exposed to the test substance for 30 days during which pubertal indices are measured. After necropsy, reproductive and thyroid tissues are weighed and evaluated histologically and serum taken for hormone analysis. The purpose of this review was to examine the available literature on pubertal development in the male rat and evaluate the efficacy of the proposed protocol for identifying endocrine-disrupting chemicals. The existing data indicate that this assessment of puberty in the male rat is a simple and effective method to detect the EDC activity of pesticides and toxic substances.