Toxicity and metabolism of monoethylhexyl phthalate and diethylhexyl phthalate: a survey of recent literature

Trophic transfer of nanoplastics and di(2-ethylhexyl) phthalate in a freshwater food chain (Chlorella Pyrenoidosa-Daphnia magna-Micropterus salmoides) induced disturbance of lipid metabolism in fish

Nanoplastics and di(2-ethylhexyl) phthalate (DEHP) are ubiquitous emerging contaminants that are transferred among organisms through food chain in the ecosystem. This study evaluated the trophic transfer of polystyrene nanoplastics (PSNPs) and DEHP in a food chain including Chlorella pyrenoidosa, Daphnia magna and Micropterus salmoides (algae-crustacean-fish) and lipid metabolism at a higher trophic level in fish. Our results showed that the PSNPs and DEHP accumulated in C. pyrenoidosa or D. magna were transferred to the M. salmoides, of which the DEHP were not biomagnified, while the PSNPs were trophically amplified by the food chain. It is suggested that more PSNPs might be accumulated by higher level consumers in a longer food chain. Additionally, the trophic transfer of PSNPs and DEHP resulted in antioxidant response and histopathological damage in M. salmoides. Moreover, the lipid biochemical parameters and lipid metabolism related genes (fasn, hsl, cpt1a, atgl, apob, fabp1, lpl, cetp) of M. salmoides were significantly affected, which indicated disturbance of lipid metabolism. This study offers great insight into the transfer of contaminants by trophic transfer and their negative effects on organisms at higher trophic levels, which cause human exposure to MNPs and organic contaminants in the ecosystem.

Di-(2-ethylhexyl) phthalate increases plasma glucose and induces lipid metabolic disorders via FoxO1 in adult mice

Di-(2-ethylhexyl) phthalate (DEHP), an endocrine-disrupting chemical (EDC) commonly used as a plasticizer, is responsible for widespread environmental pollution. Epidemiological and experimental data implicate DEHP and its metabolite mono(2-ethylhexyl) phthalate (MEHP) in the occurrence and development of metabolic syndrome. However, the specific effects and potential mechanisms of action of DEHP on glucose and lipid metabolism in adults are currently unclear. In the current study, adult male mice were continuously exposed to DEHP (0, 5, and 25 mg/kg/day) via oral administration and changes in glucose and lipid metabolism explored. Notably, exposure to DEHP led to a significant increase in plasma glucose and hepatic lipid accumulation but had no effect on insulin secretion. Western blot and real-time quantitative PCR showed that DEHP induced insulin resistance and promoted gluconeogenesis and lipid accumulation via overexpression of forkhead box protein O1 (FoxO1), in keeping with hepatic RNA sequencing data. Variations in gut microbiota aggravated these effects while inhibition of FoxO1 reversed the adverse effects of DEHP. Our findings support a key role of FoxO1 in disorders of glucose and lipid metabolism caused by DEHP.

Effect of phthalates exposure during perinatal period on hormonal profile in Mexican males during their first months of life

Phthalates affect development of male reproductive system acting as an antiandrogenic agents. We sought to explore if perinatal exposure to phthalates could alter male hormone levels in humans during the first months of life. A cohort of 83 pregnant women and their male infants were studied. Five phthalate metabolites were measured in the mother's urine during the first, second, and third trimesters of pregnancy and during the first, third, and sixth months of life in the infants. Luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone and inhibin B were analyzed. Association between phthalate exposure and hormone variation was assessed using regression models for longitudinal data. Mono-butyl phthalate reduced FSH concentration (ß = -0.0012 international units [IU]/L, p < 0.01), mono-ethylhexyl phthalate reduced inhibin B (ß = -0.0094 pg/mL, p = 0.02), monoethyl phthalate reduced testosterone (ß = -0.0071 ng/L, p = 0.07), mono-ocytl phthalate reduced LH (ß = -0.0041 IU/L, p = 0.13). No effects were observed for exposure to mono-methyl phthalate. Our results are consistent with the findings in animal and human studies. Special precaution should be taken when measuring phthalate exposure in susceptible populations such as pregnant women and infants.

Phthalates exposure during pregnancy a study in a Mexican cohort

A prospective cohort study was conducted to measure the concentration levels of three primary phthalate metabolites (MBP, MEHP, MEP) during pregnancy in a group of women from the State of Mexico. The urinary concentration levels of the three phthalate primary metabolites were measured by gas chromatography mass spectrometry during the first, second and third trimesters of pregnancy. The geometric mean and 95 % CI for MBP was 20.38 μg/mL (15.35-27.09); for MEHP 13.43 μg/mL (8.93-20.20), and MEP 52.47 μg/mL (39.88-69.04) adjusted to one g of creatinine. No significant trends were observed among the studied metabolites during the pregnancy period. MBP was higher in less educated women, while women who resided in industrialized zones showed higher levels of MEHP and MEP than women from non-industrialized zones. Consumption of plastic bottled beverages was associated with MBP and MEHP phthalate exposure. Women who used non-registered brands of plastic food containers for storage or for microwave oven use showed the highest levels of MBP and MEP phthalates. The pregnant women in our study were exposed to the three studied primary phthalate metabolites, and this could present a risk to their newborns. To better integrate public health policies, major exploration of potential exposure sources and effects at the regional level is required.

System Biology-Guided Chemical Proteomics to Discover Protein Targets of Monoethylhexyl Phthalate in Regulating Cell Cycle

Chemical proteomics methods have been used as effective tools to identify novel protein targets for small molecules. These methods have great potential to be applied as environmental toxicants to figure out their mode of action. However, these assays usually generate dozens of possible targets, making it challenging to validate the most important one. In this study, we have integrated the cellular thermal shift assay (CETSA), quantitative proteomics, metabolomics, computer-assisted docking, and target validation methods to uncover the protein targets of monoethylhexyl phthalate (MEHP). Using the mass spectrometry implementation of CETSA (MS-CETSA), we have identified 74 possible protein targets of MEHP. The Gene Ontology (GO) enrichment integration was further conducted for the target proteins, the cellular dysregulated proteins, and the metabolites, showing that cell cycle dysregulation could be one primary change due to the MEHP-induced toxicity. Flow cytometry analysis confirmed that hepatocytes were arrested at the G1 stage due to the treatment with MEHP. Subsequently, the potential protein targets were ranked by their binding energy calculated from the computer-assisted docking with MEHP. In summary, we have demonstrated the development of interactomics workflow to simplify the redundant information from multiomics data and identified novel cell cycle regulatory protein targets (CPEB4, ANAPC5, and SPOUT1) for MEHP.

A Novel Mechanism of Monoethylhexyl Phthalate in Lipid Accumulation via Inhibiting Fatty Acid Beta-Oxidation on Hepatic Cells

Monoethylhexyl phthalate (MEHP) is one of the main active metabolites of the plasticizer di(2-ethylhexyl) phthalate. It has been known that MEHP has an impact on lipolysis; however, its mechanism on the cellular lipid metabolism remains largely unclear. Here, we first utilized global lipid profiling to fully characterize the lipid synthesis and degradation pathways upon MEHP treatment on hepatic cells. Meanwhile, we further identified the possible MEHP-targeted proteins in living cells using the cellular thermal shift assay (CETSA) method. The lipidomics results showed that there was a significant accumulation of fatty acids and other lipids in the cell. The CETSA identified 18 proteins and fatty acid β-oxidation inhibition pathways that were significantly perturbed. MEHP's binding with selected proteins HADH and HSD17B10 was further evaluated using molecule docking, and results showed that MEHP has higher affinities as compared to endogenous substrates, which was further experimentally confirmed in the surface plasma resonance interaction assay. In summary, we found a novel mechanism for MEHP-induced lipid accumulation, which was probably due to its inhibitive effects on the enzymes in fatty acid β-oxidation. This mechanism substantiates the public concerns on the high exposure level to plasticizers and their possible role as an obesogen.

MEHP/ethanol co-exposure favors the death of steatotic hepatocytes, possibly through CYP4A and ADH involvement

Liver steatosis has been associated with various etiological factors (obesity, alcohol, environmental contaminants). How those factors work together to induce steatosis progression is still scarcely evaluated. Here, we tested whether phthalates could potentiate death of steatotic hepatocytes when combined with ethanol. Pre-steatotic WIF-B9 hepatocytes were co-exposed to mono (2-ethylhexyl) (MEHP, 500 nM; main metabolite of di (2-ethylhexyl) phthalate or DEHP) and ethanol (5 mM) for 5 days. An increased apoptotic death was detected, involving a DNA damage response. Using 4-Methypyrazole to inhibit ethanol metabolism, and CH-223191 to antagonize the AhR receptor, we found that an AhR-dependent increase in alcohol dehydrogenase (ADH) activity was essential for cell death upon MEHP/ethanol co-exposure. Toxicity was also prevented by HET0016 to inhibit the cytochrome P450 4A (CYP4A). Using the antioxidant thiourea, a role for oxidative stress was uncovered, notably triggering DNA damage. Finally, co-exposing the in vivo steatosis model of high fat diet (HFD)-zebrafish larvae to DEHP (2.56 nM)/ethanol (43 mM), induced the pathological progression of liver steatosis alongside an increased Cyp4t8 (human CYP4A homolog) mRNA expression. Altogether, these results further emphasized the deleterious impact of co-exposures to ethanol/environmental pollutant towards steatosis pathological progression, and unraveled a key role for ADH and CYP4A in such effects.

Simultaneous determination of 22 phthalate esters in polystyrene food-contact materials by ultra-performance convergence chromatography with tandem mass spectrometry

A method for the determination of 22 phthalate esters in polystyrene food-contact materials has been established using ultraperformance convergence chromatography with tandem mass spectrometry. In this method, 22 phthalate esters were analyzed in <3.5 min on an ACQUITY Tours 1-AA column by gradient elution. The mobile phase, the compensation solvent, the flow rate of mobile phase, column temperature, and automatic back pressure regulator pressure were optimized, respectively. There was a good linearity of 20 phthalate esters with a range of 0.05-10 mg/L, diisodecyl phthalate and diisononyl phthalate were 0.25-10 mg/L, and the correlation coefficients of all phthalates were higher than 0.99 and those of 16 phthalates were higher than 0.999. The limits of detection and the limits of quantification of 15 phthalates were 0.02 and 0.05 mg/kg, meanwhile diallyl phthalate, diisobutyl phthalate, dimethyl phthalate, di-n-butyl phthalate, and di(2-ethylhexyl) phthalate were 0.05 and 0.10 mg/kg, and diisodecyl phthalate and diisononyl phthalate were 0.10 and 0.25 mg/kg. The spiked recoveries were in the range of 76.26-107.76%, and the relative standard deviations were in the range of 1.78-12.10%. Results support this method as an efficient alternative to apply for the simultaneous determination of 22 phthalate esters in common polystyrene food-contact materials.

Adsorption of benzoic acid, phthalic acid on gold substrates studied by surface-enhanced Raman scattering spectroscopy and density functional theory calculations

Benzoic acid (BA) and phthalic acid (PTA) are the simplest aromatic carboxylic acids, and they can be regarded as typical model compounds in investigating the interaction of aromatic carboxylic acids with metal surfaces by use of SERS spectroscopy. In this work, we have investigated the structure and adsorption behavior of benzoic acid and phthalic acid on the gold surface with combination of SERS and DFT calculation methods. The experimental results show that both BA and PTA may be adsorbed on the Au surface with a bidentate bridging structure, namely, the carboxylate group(s) being bound to gold via two oxygen atoms in the carboxylate group(s). Comparison of the observed SERS and predicted spectra of the complexes of these two substances with Au atoms indicates that BA is favorable to adsorb on the gold surface with a vertical orientation rather than a flat one, and PTA could "stand up" on the Au surface as a slight tilt with a two-legged geometry, i.e. all four oxygen atoms in two carboxylate groups interact on the metal surface. Apart from that, we compare the discrepancy of SERS spectra between those two molecules, which could be taken as a potential analysis technique in food safety field.

Presence of phthalate esters in intravenous solution evaluated using gas chromatography-mass spectrometry method

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer widely used in the production of poly-(vinyl) chloride (PVC) materials. It is a reproductive and developmental toxicant in animals and a suspected endocrine modulator in humans. DEHP is not covalently bound within the PVC molecule, which is why migration into a suitable medium can be expected. Since application of infusion solutions is one of the most common medical treatments, the objective of this study was to determine the migration of phthalates from softened PVC storage bags into infusion solution in different time periods within one year from date of production using a gas chromatography-mass spectrometry method. The measured values of DEHP ranged between 0.22 and 14.00 µg l(-1) , but the unexpected presence of other phthalate esters was also detected. It was concluded that values obtained in infusion solutions match the reference data and represent a minor risk for the patient. The presence of other phthalate esters leads to the conclusion that the pharmacopeic requirement for polymer cleanness was not fully met. Since phthalate esters are among the most extensively used industrial chemicals and are widely distributed in the environment, special precautions and further monitoring should be conducted to minimize any possible health risks.

Effects of di-iso-butyl phthalate on testes of prepubertal rats and mice

Di-iso-butyl phthalate (DiBP), a special plasticizer, is used as a substitute for di(n-butyl) phthalate (DBP). The effects of DiBP on testes in prepubertal rodents still remain to be obscure. Testicular toxicity of DiBP was investigated in 21-day-old Sprague-Dawley rats and C57BL/6N mice, using with in situ TUNEL method. For an acute exposure experiment, animals were once given DiBP at various concentrations by oral gavage. For a subchronic exposure experiment, they were daily given DiBP at various concentrations for consecutive 7 days. Controls were treated with corn oil under the same condition. For a recovery experiment, rats were once given DiBP (1000 mg/kg), and were sacrificed at day 1 to 8 after administration. Furthermore, the disorder of vimentin filaments in Sertoli cells after daily administration of DiBP (500 mg/kg) for consecutive 7 days in rats also identified by immunohistochemistry using anti-vimentin antibody. As a result, the present study demonstrated that DiBP can induce testicular atrophy in rats due to the increase of TUNEL-positive spermatogenic cells in both acute and subchronic exposure experiments. At the same time, the disorder of vimentin filaments in Sertoli cells was recognized. However, no such damages could be found in mouse testis. For the recovery experiment, the testis weight and testicular morphology returned to normal at day 6 after administration. In conclusion, the present study indicates that DiBP causes the significant increase of TUNEL-positive spermatogenic cells and the disorder of vimentin filaments in Sertoli cells in rats and that DiBP shows a species-specific toxicity.

Phagocytosis plays an important role in clearing dead cells caused by mono(2-ethylhexyl) phthalate administration

The role of phagocytosis in eliminating apoptotic spermatogenic cells caused by mono(2-ethylhexyl) phthalate (MEHP) was studied. Twenty-one-day-old C57Bl/6N male mice were given a single dose of 800 mg/kg MEHP in corn oil by oral gavage and sacrificed at 1, 3, 5, 7 and 9 days after initial exposure. At the same time, the role of phagocytosis in MEHP related apoptosis was examined using microinjection of annexin V into the seminiferous tubules of living mice. Results showed that mice treated with MEHP had a lower rate of testis weight gain (lower regression line) and a significant TUNEL-positive spermatogenic cell number compared to control. However, this incident was reversible, and the number of TUNEL-positive cells returned to normal after 9 days. Mice microinjected with annexin V and later treated with MEHP showed a large amount of TUNEL-positive cells compared to mice treated with MEHP only. This clearly proves that phagocytosis plays an efficient and highly important role in eliminating dead cells in the injured testis of mice treated with MEHP.

Di-2-ethylhexyl phthalate in the fruits ofBenincasa hispida

Di-2-ethylhexyl phthalate (DEHP) is a commonly used plasticizer that is harmful to human health. magnetic resonance spectroscopy from the edible fruit flesh of Benincasa hispida (wax gourd) of the plant family Curcurbitaceae. The DEHP content of seven wax gourd samples collected from southern and northern provinces in China was determined as (mean +/- SD): 18.3 +/- 0.43, 2.64 +/- 0.44, 44.0 +/- 0.34, 62.5 +/- 0.48, 52.0 +/- 0.42, 58.3 +/- 0.55 and 75.5 +/- 0.63 mg kg-1 fresh weight, respectively, indicating that most wax gourds were severely contaminated with DEHP.

Application of single-drop microextraction to the determination of dialkyl phthalate esters in food simulants

A fast and simple method, using static single-drop microextraction (SDME), has been developed to facilitate the identification and quantification of seven dialkyl phthalate esters in the three aqueous food simulants. The simulants were: A, distilled water; B, 3% (w/v) acetic acid/water; and C, 15% (v/v) ethanol/water. The extraction is performed by simply suspending a drop of organic solvent in the aqueous sample using a conventional gas chromatography (GC) microsyringe. Following extraction, the organic phase is withdrawn into the syringe and analyzed by gas chromatography and flame ionization detection (FID). The optimized method yields a linear calibration curve over three orders of magnitude for all the simulants, and method detection limits (MDLs) allowing detection of all the studied compounds at concentrations below migration limits established by the European Union. The accuracy of the SDME method was tested and compared to that of solid-phase microextraction (SPME) by recovery experiments using spiked samples, with results ranging from 85 to 115% in most cases.

DEHP enrichment in the surface microlayer of a small eutrophic lake

Investigation of di-2-ethylhexyl phthalate (DEHP) in the surface microlayer (SM) and subsurface water (SSW) of a small eutrophic lake was carried out from April to June 2002. Results obtained from the field samples showed that tens to several hundred mug/L of DEHP was found in each sample of SM and SSW, indicating that the lake has been polluted by DEHP. Linear regression analysis showed that concentrations of DEHP were more strongly correlated with sampling temperature than with chlorophyll a concentrations. Correlation between DEHP concentrations and total phosphor concentrations was also obtained. Enrichment factors (EFs) of DEHP in the SM comparing with the corresponding SSW were ranging over 0.85-2.12 with an average of 1.35. DEHP EFs were significantly related to both enrichment of chlorophyll a in the SM and sampling temperature.

Determination of isotopically labelled monoesterphthalates in urine by high performance liquid chromatography-mass spectrometry

A method of analysis for monoesters of phthalic acid ('monoesterphthalates') in human urine has been developed. The method was needed to determine the hydrolysis and excretion efficiency of isotopically-labelled phthalate diesters ('phthalates') when they were fed to volunteers as part of a biomarker study to estimate total exposure to phthalates. The targeted substances were 13C-monobutylphthalate (MBP), 2H4-monobutylphthalate (MBP), 2H4-monobenzylphthalate (MBeP), 13C-monocyclohexylphthalate (MCHP), 13C-monoethylhexylphthalate (MEHP), and 13C-monoisodecylphthalate (MIDP). The monoesters in urine were deconjugated enzymatically, extracted into solvent, and then determined by high performance liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure chemical ionisation in the negative ion mode. The limits of determination were 10 ng ml(-1) for MBP, MCHP, MBeP and MEHP, and 40 ng ml(-1) for MIDP. The recovery from urine spiked at 100 ng ml(-1) was in the range from 70 to 85% except for MIDP which was lower at 55%. The between-batch reproducibility of the analysis was in the range 8 to 17% (n = 6 batches on separate days).

A biomarker approach to measuring human dietary exposure to certain phthalate diesters

Three groups of eight volunteers were administered stable isotope-labelled phthalate diesters in a single dose and the amount of the corresponding phthalate monoesters excreted in the urine was measured. Amongst the phthalates administered were the symmetrical dibutyl-, di-2-ethyl- and diisooctyl- phthalates along with the unsymmetrical benzylbutylphthalate. The control group received no dose, the low dose group received 168-255 microg of each phthalate and the high dose group received 336 to 510 microg of each phthalate. The excreted phthalate monoesters were measured by LC-MS following hydrolysis of conjugates. The bulk of phthalate monoester was excreted in the first 24 hour period following the dose. For dibutylphthalate, 64% and 73% on a mole basis of the low, and high dose respectively was excreted as monobutylphthalate. For dioctylphthalate (sum of the 2-ethylhexyl and the isooctyl species) the yield was 14 and 12% of the low and high dose excreted as monooctylphthalate. For benzylbutylphthalate, 67% and 78% was eliminated as monobenzylphthalate and only 6% (measured for the high dose only) was eliminated as monobutylphthalate. These conversion factors can be used in future studies to assess exposure to phthalate esters via measuring urinary levels of the monoester metabolites.

A critical assessment of some biomarker approaches linked with dietary intake

In this review many examples are given of the complexities involved in using some biomarkers in relation to assessing the effects of dietary exposure, when there is frequently a need to determine changes following long-term low level exposure to dietary components. These range from understanding why the biomarker might be valuable and how best it can be measured, to the pitfalls which can occur in the interpretation of data. Analytical technique is considered in relation to folate and selenium, and flavonoid and carotenoid species are used to illustrate how the metabolism of a compound may alter the validity or adequacy of a marker. Vitamin A is discussed in relation to the difficulties which can arise when there are several biomarkers that may be available to assess exposure to one nutrient. Vitamin B12 is discussed in relation to the dietary choices made by individuals. Possible interactions and the role of measuring total antioxidant capacity is considered in some detail. In contrast to most nutrients, there is a marked lack of biomarkers of either exposure or effect for most non-nutrients. The role of biological effect monitoring is considered for dietary contaminants, fumonisins and polyhalogenated aromatic hydrocarbons. Aflatoxins are discussed to exemplify food contaminants for which the biomarker approach has been extensively studied. Finally some compounds which are deliberately added to foods and some which appear as processing contaminants are each considered briefly in relation to the requirement for a biomarker of exposure to be developed.

A single dose of Di-(2-ethylhexyl) phthalate in neonatal rats alters gonocytes, reduces sertoli cell proliferation, and decreases cyclin D2 expression

In this study, we explored the impact on both Sertoli cells and gonocytes of a single, relatively low dose of di-(2-ethylhexyl) phthalate (DEHP; 20-500 mg/kg) administered in vivo to 3-day-old rat pups. In parallel, we assessed the potential for two immediate metabolites of DEHP to produce similar testicular changes and began to explore the possible mechanisms involved. Morphological examination revealed the presence of many abnormally large, multi-nucleated germ cells by 24 h posttreatment with DEHP and with its metabolite, mono-ethylhexyl phthalate (MEHP), but not with another metabolite, 2-ethylhexanol (2-EH; all at 1.28 mmol/kg) or with vehicle alone. These cells persisted through 48 h posttreatment, the longest time point examined in our study. We also assessed the rate of Sertoli cell proliferation in pups at intervals after dosage with either chemical or vehicle by administering bromodeoxy uridine (BrdU) 3 h before euthanasia. By 24 h after treatment with DEHP or MEHP, but not 2-EH or vehicle, the number of BrdU-labeled Sertoli cells was obviously diminished in testicular sections. Quantitation of DEHP-treated pups and controls indicates that a dose-response relationship exists between chemical treatment and labeling index (LI) of Sertoli cells, with a LI at the highest DEHP dose tested that was only 20% of that in controls. In addition, when we examined the time course of the effect of an intermediate dose of DEHP, we found that there the LI of Sertoli cells rebounds by 48 h after dosage, when we found the rate of proliferation in treated pups to be significantly higher than in controls. We also explored the potential mechanism involved in the response to DEHP and found serum levels of FSH to be unaffected by the chemical. In addition, study of cell cycle-related proteins including p27kip1 and cyclins D1, D2, and D3 with Western and Northern analysis indicated that cyclin D2 mRNA is specifically down-regulated by DEHP in a dose-dependent manner, and this decrease is manifest as a small, transient but reproducible reduction in the amount of cyclin D2 protein detectable in samples from treated pups compared to controls. Our findings characterize the changes in neonatal Sertoli cells and gonocytes that follow in vivo to low levels of DEHP and its metabolite, MEHP, as well as providing new information on the underlying mechanism and highlighting the extreme sensitivity of the neonatal testis to injury by this toxicant.

Effects of relatively low levels of mono-(2-ethylhexyl) phthalate on cocultured Sertoli cells and gonocytes from neonatal rats

Di-(2-ethylhexyl) phthalate (DEHP), one of the abundant man-made environmental chemicals, induces testicular damage in both developing and adult animals. However, the nature and mechanism underlying the action of phthalates on testicular development remain largely unexplored. In the present study, we used cocultures of neonatal Sertoli cells and gonocytes (precursors of spermatogonia) to characterize in detail the effects of mono-(2-ethylhexyl) phthalate (MEHP; the active metabolite of DEHP) on these cells and to explore the underlying mechanism(s). Sertoli cells and gonocytes were isolated from rat pups on the 2nd day after birth, cocultured, and exposed to MEHP at concentrations of 0.01, 0.1, or 1.0 microM, or to 0.5% DMSO (vehicle control), or 10 microM DEHP (negative control) for a total of 48 h. We found that exposure to MEHP induced gonocyte detachment from the Sertoli cell monolayers in a time- and dose-dependent manner. When exposed to 1.0 microM MEHP, many gonocytes started to detach after 12 h of exposure and most gonocytes were lost during the media change at 24 h. Gonocyte detachment was also observed in cocultures treated with 0.1 microM MEHP for 24 h of exposure, but not in cultures treated with 0.01 microM MEHP for 48 h. Detached gonocytes were viable as indicated by their ability to exclude trypan blue. Furthermore, when proliferation of cultured Sertoli cells was detected by BrdU labeling and subsequently quantified, we found that exposure to 0.1 or 1.0 microM MEHP for 48 h resulted in a decrease in labeling indices of 33.6 and 83.6%, respectively, compared to the vehicle control (p < 0.01), while the labeling index was unchanged by treatment with 0.01 microM MEHP. In addition, we also tested the potential effect of MEHP on FSH-stimulated Sertoli cell proliferation by simultaneously treating cultures with 200 ng/ml human FSH and different concentrations of MEHP for 48 h. Exposure to 0.1 or 1.0 microM MEHP resulted in decreases of 24.2 and 74.2%, respectively, in FSH-stimulated Sertoli cell proliferation (p < 0. 01). Furthermore, MEHP also inhibited dibutyl cAMP-stimulated Sertoli cell proliferation, regardless of whether dibutyl cAMP was added to the cultures before or at the same time as MEHP. Finally, addition of FSH or dibutyl cAMP had no effect on MEHP-induced gonocyte detachment, and none of the observed effects on either Sertoli cells or gonocytes were detected in control cultures treated with 0.5% DMSO only or with 10 microM DEHP. Therefore, short exposure to low levels of MEHP disrupted adhesion of gonocytes to Sertoli cells and inhibited both basal and FSH-stimulated Sertoli cell proliferation in a dose-dependent manner. The lowest effective dose of MEHP in vitro was 0.1 microM, which is about 10- to 1, 000-fold lower than the dose shown to affect Sertoli cells from prepubertal animals. Moreover, our data indicate that MEHP impairs division of neonatal Sertoli cells by acting at a post-cAMP site in the FSH-response pathway or via a mechanism independent of FSH. These data provide direct new evidence that relatively low levels of MEHP disrupt Sertoli cell-gonocyte physical interactions and suppress Sertoli cell proliferation in neonates via mechanisms specific to neonatal testis where the foundations of adult fertility are established. The results also highlight the neonatal period of testicular development as one particularly sensitive to environmental chemicals.

Ingestion of sludge applied organic chemicals by animals

Intake of sludge-borne chemicals is related to the crop and animal management systems, the species and physiological status of animals, and the properties of the chemicals. The greatest intake occurs when sludge is applied to established crops and animals have immediate access. Intake is reduced when access is delayed to allow losses by weathering and dilution by plant growth, or when sludge is incorporated into soil because vapour transport from soil to plants and lower concentrations at the surface reduce intake via soil ingestion. Animals that consume forage are the most subject to contaminant exposure, which is maximized when pasture is the major component of the diet because soil ingestion is an additional exposure pathway. Of the many organic contaminants in sludges, only lipophilic halogenated hydrocarbons accumulate in animal tissues and products. Compounds like phthalate esters, PAHs, acid phenolics, nitrosamines, volatile aromatics, and aromatic surfactants are metabolized and do not accumulate. Among halogenated hydrocarbons, compounds with low degrees of halogenation are metabolized and do not accumulate, but higher degrees of halogenation block metabolism, and concentrations in milk and tissue fat may be several-fold greater than in the diets.

Chromatographic fractionation and analysis by mass spectrometry of conjugated metabolites of bis(2-ethylhexyl)phthalate in urine

Mono(2-ethylhexyl)phthalate (MEHP), the primary metabolite of the plasticizer bis(2-ethylhexyl)phthalate (DEHP), was given to guinea pigs and mice and the methods for the isolation, separation and analysis of its metabolites in urine were developed. Following solid-phase extraction with octadecylsilane-bonded silica, individual metabolites were purified and separated using a combination of ion-exchange chromatography on lipophilic gels and reversed-phase high-performance liquid chromatography. Analysis of intact conjugates, as well as nonconjugated metabolites, was performed by fast atom bombardment mass spectrometry (FAB-MS) and, after derivatization, by gas chromatography-mass spectrometry. Enzymatic methods were used for further characterization. The study confirms glucuronidation as the major conjugation pathway for MEHP in the investigated species. Although less important quantitatively, glucosidation is shown to be an alternative conjugation pathway in mice. The methods developed were applied to a sample of urine from a hyperbilirubinemic newborn infant subjected to DEHP-exposure in conjunction with an exchange transfusion. It was demonstrated that metabolites of DEHP were excreted in amounts which could be analyzed by FAB-MS.

Poly(vinyl chloride) formulations: acute toxicity to cultured human cell lines

Two quantitative cytotoxicity assay methods (cytoplasmic retention of carboxyfluorescein and mitochondrial cleavage of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)) have been used to evaluate the response of two cultured human cell lines; HepG2 (hepatoma) and W138va13 (transformed lung fibroblasts) to extracts of a range of poly(vinyl chloride) (PVC) formulations. Two plasticizers; di(2-ethylhexyl)phthalate (DEHP) and di-isooctyl phthalate and a range of tin and non-tin stabilizers were incorporated in the study. Only those formulations containing both a plasticizer and a tin-based stabilizer produced extracts which were toxic. Extracts of those formulations which contained both plasticizer and dibutyl tin dimaleate stabilizer were toxic to both cell lines in both assay methods. Extracts of a formulation containing plasticizer and a dioctyl tin mercaptide were toxic to both cell lines in the carboxyfluorescein assay but were only toxic to the WI38va13 cells in the MTT assay. The WI38va13 cells were generally more sensitive to the extracts than the HepG2 cells. When serial dilutions of the extracts were evaluated, the carboxyfluorescein assay proved to be the more sensitive of the two. The acute toxicity of extracts of these PVC formulations cannot be directly attributed to the plasticizers or to the tin stabilizers. It is likely that a synergistic mechanism, such as plasticizer facilitated extraction of the tin stabilizer, exists.

Transport of organic environmental contaminants to animal products

A large number of chemical contaminants potentially may be present in agricultural environments, leading to exposure of animals and potential residues in animal products. The contamination may be either widespread, as a result of aerial transport of industrial emissions, or localized, as a result of accidental emissions and spills, improper waste disposal, contaminants in useful products, and areas of past use of products now banned. The halogenated hydrocarbons, including the polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and persistent organochlorine insecticides remaining from past use, are the contaminants of most concern. Depending on the degree and pattern of chlorine substitution, these compounds are resistant to degradation and tend to accumulate in the fat of animals and their products. Other classes of environmental contaminants as exemplified by the PAHs, phthalate esters, acid phenolics, and nitrosamines also may occur widely in the environment. These compounds are unlikely to be transported to animal products because the compounds are water-soluble or can be metabolized to water-soluble products, which are excreted in the urine and thus do not bioaccumulate in products such as milk and meat. The points of entry of environmental contaminants into agricultural environments usually are plants and soils. Lipophilic compounds such as the halogenated hydrocarbons are not taken up and translocated by plants. Contamination of plants is mainly a surface phenomenon resulting from aerial deposition of emissions or deposition of compounds volatilized from the surface of contaminated soil. Thus, fibrous roughages used primarily in feeding cattle and other ruminants will be the most important pathway of animal exposure and transport to human foods. The second pathway of animal exposure is by ingestion of contaminated soil while grazing or when confined to unpaved facilities. As in the case of feed sources, cattle is the species most vulnerable to exposure by the soil ingestion pathway under most commercial management systems, but poultry and swine are more vulnerable in those infrequent situations in which these species have access to contaminated soil.

Di(2-ethylhexyl)phthalate-induced changes in liver estrogen metabolism and hyperplasia

Exposure to a common phthalate, di(2-ethylhexyl)phthalate (DEHP), is associated with liver hyperplasia prior to the development of hepatocellular carcinoma in rodents. The exact mechanism of liver hyperplasia as well as tumorigenesis by this agent is not known. Since other lines of evidence point to estrogens as mediators of liver hyperplastic changes, we investigated whether DEHP exposure might alter hepatic estrogen metabolism and induce hyperplasia. Male Fischer 344 rats were fed either control or 1.2% DEHP-containing diets and sacrificed after 4, 8 and 16 weeks of exposure; activities of several sex hormone-responsive markers were measured. Rats fed DEHP had significantly increased serum estradiol levels, but hepatic activity of both cytosolic and nuclear estrogen receptor (ER) was significantly reduced. The serum content of ceruloplasmin, an estrogen-responsive protein synthesized by the liver, was also reduced, perhaps as a consequence of loss of ER activity. The rise in serum estradiol in DEHP-treated rats may be explained by the observation that these rats showed significant losses in hepatic activity of both a major male estrogen-metabolizing enzyme, estrogen 2-hydroxylase, and a male-specific estrogen-sequestering protein. In contrast to reductions in these activities, the expression of proliferating cell nuclear antigen and mRNAs for both ER and fos increased significantly as a result of exposure to DEHP. Our results suggest that changes in estrogen metabolism, receptor activity and activation of genes for cell proliferation are among the earliest metabolic alterations induced by DEHP. These changes together with the induced hyperplasia could play a crucial role in hepatocellular carcinoma development as a result of continuous exposure to DEHP.

Testicular effects of di-n-butyl phthalate (DBP): biochemical and histopathological alterations

Di-n-butyl phthalate (DBP) was administered to young male rats by gavage at the doses of 250, 500 and 1,000 mg/kg body weight/day for 15 days. A significant decrease in testes weight was observed at 500 and 1,000 mg/kg doses of DBP. Histopathological examination revealed marked degeneration of seminiferous tubules. The activities of testicular enzymes associated with postmeiotic spermatogenic cells, such as sorbitol dehydrogenase and acid phosphatase, were decreased significantly, while that of lactate dehydrogenase was significantly increased, coincident with degeneration of spermatogenic cells. The activities of enzymes associated with premeiotic spermatogenic cells, Sertoli cells or interstitial cells, beta-glucuronidase, gamma-glutamyl transpeptidase and glucose-6-phosphate dehydrogenase were significantly increased. Thus the alterations in activity of these testicular cell specific enzymes suggest that DBP exposure during early life could affect the testicular functions.

Mechanism of testicular atrophy induced by di-n-butyl phthalate in rats. Part 1

Repeated oral doses of di-n-butyl phthalate (DBP) to male rats caused a decrease in testicular fructose and glucose and a sloughing of the germ cells on the first day of treatment. On day 2, more severe sloughing was seen and was accompanied by decreases in testicular iron and zinc levels and increases in the level of inositol and cholesterols. The sloughing was followed by atrophy, accompanied by dissociation of the germ cells from the Sertoli cells and reduction of triglycerides, cholesterols and phospholipids containing choline and ethanolamine residues in the testis.

Effects of co-administration of di(2-ethylhexyl)phthalate and testosterone on several parameters in the testis and pharmacokinetics of its mono-de-esterified metabolite

The administration of 1 g/kg di(2-ethylhexyl)phthalate (DEHP) or 5 mg/kg testosterone for 1 week did not affect the testicular and prostatic gland weights in rats. However, co-administration of DEHP and testosterone induced severe testicular atrophy accompanied by a decrease of zinc concentration in the testis and reduction of the activity of testicular specific lactate dehydrogenase isozyme. These changes were similar to the results of high dose administration of DEHP alone. Values of biological half-life and area under the concentration-time curve (AUC) of mono(2-ethylhexyl)phthalate, the main metabolite of DEHP, in testes after a single co-administration of DEHP (p.o.) and testosterone (i.p.) were higher than those after DEHP administration alone. Results suggest that the co-administration of DEHP and testosterone enhanced the adverse effects of DEHP on testes as the result of changes in pharmacokinetic values of MEHP.

The metabolism of mono-(2-ethylhexyl) phthalate (MEHP) and liver peroxisome proliferation in the hamster

This study has investigated the in vivo metabolism of mono-(2-ethylhexyl) phthalate (MEHP), the initial metabolite of di-(2-ethylhexyl) phthalate in mammals, and the hepatic peroxisome proliferation induced by this compound following multiple oral administration to hamsters. Hamsters received [14C]-MEHP, by gavage, at doses of 50 and 500 mg/kg body wt on each of three consecutive days. Urine was collected every 24 hours and metabolite profiles were determined using capillary gas-chromatography. Multiple high doses of MEHP (500 mg/kg) induced a change in the relative proportions of metabolites produced. As previously reported for the rat, metabolites derived from sequential omega- following by beta-oxidation were increased. This increase was correlated with a parallel 3-fold increase in peroxisomal beta-oxidation--a marker for peroxisome proliferation. Hamsters were less responsive than rats to peroxisome proliferation elicited by MEHP. In contrast to the rat, a large proportion of hamster omega-1 oxidation products of MEHP (metabolites 6 and 9, mono (2-ethylhexyl-5-oxohexyl) phthalate and mono (2-ethyl-5-hydroxyhexyl) phthalate, respectively) were found as their glucuronide conjugates. This metabolic species difference may relate to differences in sensitivity to MEHP as a peroxisome proliferator. The relationship between metabolite conjugation, peroxisome proliferation and production of omega-oxidation metabolites is discussed.

Analysis by fast atom bombardment mass spectrometry of conjugated metabolites of bis(2-ethylhexyl) phthalate

Mono(2-ethylhexyl) phthalate was given to guinea pigs and mice and its metabolites were isolated from urine. A procedure consisting of sorbent extraction, ion-exchange chromatography and reversed-phase high-performance liquid chromatography was used in the purification scheme. The metabolites were analysed by fast atom bombardment mass spectrometry. It is concluded that the purification procedure is very mild and that fast atom bombardment is a useful ionization technique for intact conjugates of metabolites of bis(2-ethylhexyl) phthalate.

Di-(2-ethylhexyl)-phthalate as plasticizer in PVC respiratory tubing systems: indications of hazardous effects on pulmonary function in mechanically ventilated, preterm infants

Several PVC medical devices contain the plasticizer Di-(2-ethylhexyl)-phthalate (DEHP) in high concentration. Taken systematically DEHP only has minor toxic effects in the human organism. In three preterm infants artificially ventilated with PVC respiratory tubes unusual lung disorders resembling those observed in hyaline membrane disease, verified both clinically and radiologically, were observed during the fourth week of life. It was assumed that these lung disorders were causally related to the exposure to high doses of DEHP, which was released from the walls of the respiratory tubes. DEHP was found in the lung tissue of one patient who died of pneumothorax soon after birth after being artificially ventilated. It is strongly recommended that for disposable PVC respiratory devices the plasticizer DEHP should be used with more restrictions.

Hepatic peroxisome proliferation and hypolipidemic effects of di(2-ethylhexyl)phthalate in neonatal and adult rats

To determine the relative sensitivity of suckling rats as compared to adults to the effects of di(2-ethylhexyl) phthalate (DEHP), five daily oral doses of 0, 10, 100, 1000, or 2000 mg DEHP/kg body weight were given to male Sprague-Dawley rats beginning at 6, 14, 16, 21, 42, and 86 days of age. Twenty-four hours after the last dose, rats were sacrificed and plasma cholesterol and triglyceride levels and the activities of the hepatic peroxisomal enzymes, palmitoyl CoA oxidase and carnitine acetyltransferase, were determined. Suckling rats (1-3 weeks of age) suffered severe growth retardation at doses of 1000 mg/kg and death at 2000 mg/kg while older rats only showed decreased weight gain at 2000 mg/kg. Of particular interest was the lethality at doses of 1000 mg/kg at 14 days of age but not at 16 days or at other ages. Increases in relative liver weight and hepatic peroxisomal enzyme activities were similar in all age groups except the 14-day old group in which the increases were greater. Relative kidney weight was increased in 21-, 42-, and 86-day-old rats at the highest doses but not in younger rats. Hypolipidemia was observed only in 21-, 42-, and 86-day-old rats at doses of 1000 and 2000 mg/kg, while elevated plasma cholesterol levels were observed in 6- and 14-day-old rats at the 1000 mg/kg dose, possibly due to the dietary differences between suckling and weaned rats. The results suggest that neonatal and suckling rats are more sensitive to the lethal and growth retardation effects of DEHP than are adult rats, but the hepatic peroxisome proliferation is similar at all ages with the exception of a greater increase at 14 days of age.

Testicular atrophy induced by di(2-ethylhexyl)phthalate: changes in histology, cell specific enzyme activities and zinc concentrations in rat testis

Daily administration of 2g/kg/day di(2-ethylhexyl)phthalate (DEHP) to immature rats was found to cause testicular atrophy and reduce zinc concentration. Specific activities of testicular enzymes associated with postmeiotic spermatogenic cells, such as lactate dehydrogenase isozyme-X, hyaluronidase and sorbitol dehydrogenase, were lower than those of control by day 10, coincident with degeneration of spermatogenic cells. The specific activities of enzymes associated with premeiotic spermatogenic cells, Sertoli cells or interstitial cells (beta-glucuronidase, gamma-glutamyl transpeptidase and malate dehydrogenase) were higher than those of control by day 10. The specific activities of alcohol dehydrogenase and aldolase, zinc containing enzymes, increased after DEHP treatment in spite of the decrease in zinc concentration in the testis. In conclusion, changes in several testicular cell-specific enzymes appear to be useful biochemical markers of testicular injury induced by testicular toxicants such as DEHP. However, these changes occurred after or simultaneous with massive histological or morphological changes rather than prior to such changes.

The influence of prolonged di(2-ethylhexyl)phthalate treatment on the dolichol and dolichyl-P content of rat liver

Dolichols and glycosyl transferase activities were studied in rat liver fractions after treatment with the plasticizer di(2-ethylhexyl)phthalate, an inducer of peroxisomes and mitochondria. After a few weeks of treatment with 2% plasticizer in the diet, the amount of dolichol is more than doubled in the lysosomes but not in the microsomes while dolichyl-P decreased by 50% in the microsomes but not in the lysosomes. The isoprenoid pattern for dolichol and dolichyl-P, respectively, is modified to longer polyprenols in the two fractions as seen in the percent distribution of the individual isoprenes. Dolichyl-P and protein glycosylation by N-acetylglucosamine and mannose decreased considerably. Incubation with mixtures containing exogenous dolichyl-P did not increase protein glycosylation. Phthalate ester treatment for 2 years increased dolichol content above the control values even when the dose was decreased a hundred times, to 0.02%. The results demonstrate a compartmentalization of dolichol and dolichyl-P distribution, and the induction studies suggest that hepatocytes possess separate regulating mechanisms for these two compounds.

The metabolism of di(2-ethylhexyl) phthalate (DEHP) and mono-(2-ethylhexyl) phthalate (MEHP) in rats: in vivo and in vitro dose and time dependency of metabolism

This study investigated the in vivo metabolism of di(2-ethylhexyl) phthalate (DEHP) and mono(2-ethylhexyl) phthalate (MEHP) in rats after multiple dosing, the metabolism of MEHP in primary rat hepatocyte cultures for periods of up to 3 days, and the biotransformation of some major metabolites of MEHP. Rats were orally administered [14C]DEHP or [14C]MEHP at doses of 50 and 500 mg/kg body wt for three consecutive days. Urine was collected at 24-hr intervals, and metabolite profiles were determined. After a single dose of either compound, urinary metabolite profiles were similar to those previously reported. However, after multiple administration of both DEHP and MEHP at 500 mg/kg, increases in omega-/beta-oxidation products [metabolites I and V, mono(3-carboxy-2-ethylpropyl) phthalate and mono(5-carboxy-2-ethylpentyl) phthalate, respectively] and decreases in omega - 1-oxidation products [metabolites VI and IX, mono(2-ethyl-5-oxohexyl) phthalate and mono(2-ethyl-5-hydroxyhexyl) phthalate, respectively] were seen. At the low dose of 50 mg/kg little or no alteration in urinary metabolite profiles was observed. At 500 mg/kg of MEHP a 4-fold stimulation of CN- -insensitive palmitoyl-CoA oxidation (a peroxisomal beta-oxidation marker) was seen after three consecutive daily doses. At the low dose of 50 mg/kg only a 1.8-fold increase was noted. Similar observations were made with rat hepatocyte cultures. MEHP at concentrations of 50 and 500 microM was extensively metabolized in the rat hepatocyte cultures. Similar metabolic profiles to those seen after in vivo administration of MEHP were observed. At the high (500 microM) concentration of MEHP, changes in the relative proportions of omega- and omega- 1-oxidized metabolites were seen. Over the 3-day experimental period, omega-/beta-oxidation products increased in a time-dependent manner at the expense of omega - 1-oxidation products. At a concentration of 500 microM MEHP, a 12-fold increase of CN- -insensitive palmitoyl CoA oxidation (a peroxisomal beta-oxidation marker) was observed. At the low concentration of MEHP (50 microM) only a 3-fold increase in CN- -insensitive palmitoyl-CoA oxidation was noted and little alteration in the metabolite profile of MEHP was observed with time. Biotransformation studies of the metabolites of MEHP confirmed the postulated metabolic pathways. Metabolites I and VI appeared to be endpoints of metabolism, while metabolite V was converted to metabolite I, and metabolite IX to metabolite VI. It was also possible to reduce the transformation of metabolite X [mono(2-ethyl-6-hydroxyhexyl) phthalate] to metabolite V.(ABSTRACT TRUNCATED AT 400 WORDS)

Circulating concentrations of di(2-ethylhexyl) phthalate and its de-esterified phthalic acid products following plasticizer exposure in patients receiving hemodialysis

The degree of exposure to the plasticizer di(2-ethylhexyl) phthalate (DEHP) was assessed in 11 patients undergoing maintenance hemodialysis for the treatment of renal failure. The amount of DEHP leached from the dialyzer during a 4-hr dialysis session was estimated by monitoring the DEHP blood concentration gradient across the dialyzer. Circulating concentrations of the biologically active products of DEHP de-esterification, viz., mono(2-ethylhexyl) phthalate (MEHP) and phthalic acid, were also determined during the dialysis session. On the average, an estimated 105 mg of DEHP was extracted from the dialyzer during a single dialysis session, with a range of 23.8 to 360 mg. The rate of extraction of DEHP from the dialyzer was correlated with serum lipid content as expressed by the sum of serum cholesterol and triglyceride concentrations (r = +0.65, p less than 0.05). Time-averaged circulating concentrations of MEHP during dialysis (1.33 +/- 0.58 micrograms/ml) were similar to those of DEHP (1.91 +/- 2.11 micrograms/ml). Blood concentrations of phthalic acid (5.22 +/- 3.94 micrograms/ml) were higher than those of the esters. The length of time patients had been receiving regular dialysis treatment was not a determinant of circulating concentrations of DEHP or MEHP. In contrast, time-averaged circulating concentrations of phthalic acid correlated strongly with the duration (in years) of dialysis treatment (r = +0.92, p less than 0.001). The results indicated substantial exposure to DEHP during hemodialysis and that the de-esterified products of DEHP are present in significant concentrations in the systemic circulation. Further study is needed to assess the contribution of these metabolites to the biological actions of DEHP in man.

Determination of phthalic acid, mono-(2-ethylhexyl) phthalate and di-(2-ethylhexyl) phthalate in human plasma and in blood products

Pretreatment for the determination of phthalic acid, mono-(2-ethylhexyl) phthalate (MEHP) and di-(2-ethylhexyl) phthalate (DEHP) in human serum or plasma, and the determination of these compounds in blood products by high-performance liquid chromatography was studied. The amount of phthalic acid, MEHP and DEHP, migrated into blood products from a flexible bag, was studied. About 0.1% of DEHP in a flexible bag was found to have migrated into human platelet plasma. Most of the MEHP and phthalic acid detected in human platelet plasma was not derived from the flexible bag but was produced by enzymatic hydrolysis of the migrated DEHP. The amount of DEHP eluted into blood products from the flexible bag differed, depending upon storage time, storage temperature, etc.

Phthalic acid esters inhibit arachidonate metabolism by rat peritoneal leucocytes

Phthalic acid esters concentration-dependently inhibited the formation of both cyclo-oxygenase and lipoxygenase arachidonate products by rat peritoneal leucocytes. Phthalates are extracted by human transfusion blood stored in pvc bags, and might similarly affect the blood cells when administered to patients.