The adsorption, kinetics, and interaction mechanisms of various types of estrogen on electrospun polymeric nanofiber membranes.

This study focuses on the adsorption kinetics of four highly potent sex hormones (estrone (E1), 17ß-estradiol (E2), 17α-ethinylestradiol (EE2), and estriol (E3)), present in water reservoirs, which are considered a major cause of fish feminization, low sperm count in males, breast and ovarian cancer in females induced by hormonal imbalance. Herein, electrospun polymeric nanostructures were produced from cellulose acetate, polyamide, polyethersulfone, polyurethanes (918 and elastollan), and polyacrylonitrile (PAN) to simultaneously adsorbing these estrogenic hormones in a single step process and to compare their performance. These nanofibers possessed an average fiber diameter in the range 174-330 nm and their specific surface area ranged between 10.2 and 20.9 m2g-1. The adsorption-desorption process was investigated in four cycles to determine the effective reusability of the adsorption systems. A one-step high-performance liquid chromatography technique was developed to detect and quantify concurrently each hormone present in the solution. Experimental data were obtained to determine the adsorption kinetics by applying pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Findings showed that E1, E2 and EE2 best fitted pseudo-second-order kinetics, while E3 followed pseudo-first-order kinetics. It was found that polyurethane Elastollan nanofibers had maximum adsorption capacities of 0.801, 0.590, 0.736 and 0.382 mg g-1for E1, E2, EE2 and E3, respectively. In addition, the results revealed that polyurethane Elastollan nanofibers had the highest percentage efficiency of estrogens removal at ∼58.9% due to its strong hydrogen bonding with estrogenic hormones, while the least removal efficiency for PAN at ∼35.1%. Consecutive adsorption-desorption cycles demonstrated that polyurethane maintained the best efficiency, even after being repeatedly used four times compared to the other polymers. Overall, the findings indicate that all the studied nanostructures have the potential to be effective adsorbents for concurrently eradicating such estrogens from the environment.

Sex steroid hormone receptors of telocytes - potential key role in leiomyoma development.

BACKGROUND: Uterine leiomyoma is the most widespread benign tumor affecting women of childbearing age. There are still gaps in the understanding of its pathogenesis. Telocytes are unique cells found in more than 50 different locations inside the human body. The functional relationship between cells could clarify the pathogenesis of leiomyomata. Examination of membrane receptors on telocytes could explain their role in fibrosis, oxidative stress, and myometrial contractility. AIM: This research was conducted to assess the density of telocytes in terms of their putative role in leiomyoma formation by focusing on their correlation with the expression of estrogen and progesterone receptors. METHODS: For gross evaluation of uterine tissue samples from leiomyoma, routine histology of adjacent and unaffected myometrium was performed. Immunohistochemical analysis of c-kit, tryptase, CD34, PDGFRα (telocyte-specific), and ER and PRs (estrogen and progesterone receptors) was performed to examine uterine telocytes and the expression of sex steroid receptors. RESULTS: The decline in telocyte density in leiomyoma foci was correlated with high progesterone expression and low estrogen receptor expression. The unchanged myometrium showed the opposite correlation and balance between both steroid hormone receptors. The difference in sex steroid receptor expression is correlated with the density of uterine telocytes, which emphasizes their conductor function. CONCLUSIONS: A reduction in telocyte density and the changes in examined marker expression demonstrate the involvement of telocytes in local homeostasis. The expression of membrane receptors explicitly indicates their functional potential in the human myometrium, focusing attention on contractility and local homeostasis.

Uptake of natural and synthetic estrogens by maize seedlings.

Runoff from manure-fertilized crop fields constitutes a significant source of natural estrogens (e.g., estradiol [17ß-E2] and estrone [E1]) and synthetic estrogen mimics (e.g., zeranol [α-ZAL] and zearalanone [ZAN]) in the environment. However, processes such as sorption to and uptake by plants may inhibit the environmental mobility of hormonally active compounds. Sorption to dried root tissue was assessed in batch sorption tests, and resulting sorption isotherms were nonlinear at aqueous concentrations below 0.1 µM and linear above that limit. To evaluate the role of crop plants in the environmental fate of such compounds, we exposed hydroponic solutions containing 2 µM 17ß-E2, E1, α-ZAL, or ZAN to maize seedlings. After 22 days of exposure, α-ZAL and ZAN concentrations decreased by more than 96%, and 17ß-E2 and E1 were undetectable. The decrease in α-ZAL and ZAN concentrations in maize-exposed solutions was initially slow, but the observed uptake exceeded that predicted by sorption alone within 3 d. All four estrogens were detected in root tissues at concentrations up to 0.19 µmol g(-1), with concentrations peaking after 1-3 days of exposure. Only 17ß-E2 and α-ZAL were detected in shoots, and maximum concentrations were measured after 2 days for 17ß-E2 (0.02 µmol g(-1)) and 16 days for α-ZAL (0.8 nmol g(-1)). Concentrations measured in root and shoot tissues were 82% or less than those predicted by a partition-limited uptake model, which is attributed to transformation and possibly irreversible binding processes.

A randomized, multiple-dose parallel study to compare the pharmacokinetic parameters of synthetic conjugated estrogens, A, administered as oral tablet or vaginal cream.

OBJECTIVE: A randomized, parallel-design study was conducted to determine the pharmacokinetic profile of synthetic conjugated estrogens A (SCE-A) vaginal cream (0.625 mg SCE-A/g) when administered at intervals (1 g once daily for 7 d, then twice weekly) over a 27-day period as compared with the pharmacokinetic profile of 0.3 mg SCE-A tablets administered once daily orally for 27 days. METHODS: Blood samples were collected 48 hours before initial dosing for baseline levels and at multiple occasions during the study until 48 hours after final study dosing (day 29). Maximum plasma concentration, time to maximum plasma concentration (Tmax), and area under the curve from 0 to 24 hours were calculated at days 1, 7, and 27; in addition, area under the curve from 0 to 48 hours was calculated at days 7 and 27, and area under the curve weekly (AUCweekly) values were calculated for both groups. For purposes of comparison, ratios of AUCweekly values for vaginal cream and oral tablets were analyzed. RESULTS: Compared with an oral daily dose of 0.3 mg SCE-A, the steady-state systemic exposure from vaginal cream application was considerably less, with the cream-to-oral ratio being 0.45 for baseline-adjusted (BA) unconjugated estradiol, 0.30 for BA unconjugated estrone, and 0.04 for unconjugated equilin (AUCweekly). At steady-state, the systemic blood levels of BA unconjugated estrone, BA unconjugated estradiol and unconjugated equilin were significantly lower in women who received biweekly application of 1 gm vaginal cream compared to women who took an oral daily dose of 0.3 mg SCE-A tablet. CONCLUSIONS: After intravaginal application of SCE-A vaginal cream, absorption of estrogens was lower compared with absorption after oral administration. At steady state, the systemic exposure of equilin, estradiol, and estrone was significantly lower after twice-weekly administration of 1 g SCE-A vaginal cream compared with that achieved with an oral daily dose of a 0.3 mg SCE-A tablet.

Pharmacokinetics of a modified-release estrogen tablet.

OBJECTIVE: To determine steady-state plasma concentrations and the pharmacokinetic profile of the essential components of synthetic conjugated estrogens, B (SCE-B), particularly total estrone and delta8,9-dehydroestrone (DHE), after oral administration of a modified-released tablet. STUDY DESIGN: A randomized, multiple-dose, pharmacokinetic study of 28 healthy, postmenopausal women randomly assigned to receive two SCE-B 0.3-mg tablets or one 1.25-mg tablet daily for 14 days. Blood samples were obtained before and after dosing at designated times. Total (conjugated and free) and unconjugated estrogens, namely estrone, equilin, and delta8,9-DHE, were determined, and pharmacokinetic analysis was performed. RESULTS: Steady-state plasma levels of total estrone and total delta8,9-DHE measured on day 14 over a 24-hour period showed minor fluctuations and a similar time to maximum concentration (Tmax): mean Tmax of total estrone = 7.94 and 8.36 hours for 0.3-mg and 1.25-mg tablets, respectively; mean Tmax of total delta8,9-DHE = 7.08 and 8.36 hours for 0.3-mg and 1.25-mg tablets, respectively. Consistency in pharmacokinetic parameters was seen between the two doses of SCE-B. CONCLUSION: SCE-B 0.3-mg and SCE-B 1.25-mg tablets achieved consistent pharmacokinetic parameters and steady-state levels when administered to healthy postmenopausal women. Achieving smooth, predictable levels of component estrogens may result in more consistent relief of menopausal symptoms.

Degradation rate constants of steroids in sewage treatment works and receiving water.

Steroid estrogens are one of the most important groups of endocrine disrupting chemicals (EDCs) which can cause adverse effects on wildlife species and humans. Natural estrogens, including estrone (E1) and estradiol (E2), and synthetic estrogen 17alpha-ethinylestradiol (EE2) together contribute to most of the estrogenic activity in sewage effluents and receiving water. Degradation, particularly aerobic biodegradation was found to be the dominant removal mechanism in these environments. There are a number of factors such as temperature, pH, SRT, HRT and biomass concentration that can affect the rate of biodegradation. This paper reports the results of investigations in to the relationship between the equivalent biomass concentration and degradation rate constants for compounds E1, E2 and EE2 in various environments. It was found that a higher biomass concentration leads to higher rate constants, and relatively good linear correlations (R2 =0.73, 0.79 and 0.73) between the logarithm of the rate constants and the corresponding logarithm equivalent biomass concentration (EBC) values were obtained.

Synthetic estrogen derivatives demonstrate the functionality of intracellular GPR30.

Estrogen mediates its effects through multiple cellular receptors. In addition to the classical nuclear estrogen receptors (ERalpha and ERbeta), estrogen also signals through the seven-transmembrane G-protein-coupled receptor (GPCR) GPR30. Although estrogen is a cell-permeable ligand, it is often assumed that all GPCRs function solely as cell surface receptors. Our previous results showed that GPR30 appeared to be expressed predominantly in the endoplasmic reticulum. A critical question that arises is whether this localization represents the site of functional receptor. To address this question, we synthesized a collection of cell-permeable and cell-impermeable estrogen derivatives. We hypothesized that if functional GPR30 were expressed at the cell surface, both permeable and impermeable derivatives would show activity. However, if functional GPR30 were predominantly intracellular, like ERalpha, only the permeable ligands should show activity. Cell permeability was assessed using cells expressing ERalpha as a model intracellular estrogen-binding receptor. Our results reveal that despite exhibiting similar binding affinities for GPR30, only the cell-permeable ligands are capable of stimulating rapid calcium mobilization and phosphoinositide 3-kinase (PI3K) activation. We conclude that GPR30 expressed intracellularly is capable of initiating cellular signaling and that there is insufficient GPR30 expressed on the cell surface to initiate signaling in response to impermeable ligands in the cell lines examined. To our knowledge, this is the first definitive demonstration of a functional intracellular transmembrane estrogen receptor.

Comparison of the effects of a new conjugated oral estrogen, estradiol-3beta-glucoside, with oral micronized 17beta-estradiol in postmenopausal women.

The objective of this article is to evaluate the pharmacokinetics of serum estrone and estradiol levels in women who were taking either 17beta-estradiol-3beta-glucoside (E(2)-3beta-glucoside) or 17beta-estradiol (E(2)) daily and to examine the effects of E(2)-3beta-glucoside and E(2) on postmenopausal symptoms, gonadotropins, hepatic metabolism, and coagulation factors. Healthy postmenopausal women on estrogen who had undergone a hysterectomy were recruited. Subjects were randomly assigned to receive equivalent doses of either E(2)-3beta-glucoside or micronized E(2) for 28 days. Pharmacokinetic studies of estrone and estradiol were performed on days 1, 2, 28, and 29. Gonadotropin levels and Kupperman Index (KI) scores were determined at baseline and on treatment day 28. Mean serum estradiol and estrone concentrations in those taking E(2)-3beta-glucoside were comparable with those taking E(2). Mean baseline follicle stimulating hormone (FSH) levels were 84 +/- 27 mIU/mL and 71 +/- 24 mIU/mL in the E(2)-3beta-glucoside and E(2) groups, respectively, with significant decreases (P < 0.01) of 54 +/- 21 mIU/mL and 38 +/-18 mIU/mL, respectively, by treatment day 28. Baseline KI scores in the E(2)-3beta-glucoside group were 10 +/- 6 compared with 5 +/- 4 on treatment day 28, which is equivalent to a 50% reduction in menopausal symptoms (P = 0.003). The change in KI scores in the E(2) group was not statistically significant. Total serum estradiol and estrone levels in women taking E(2)-3beta-glucoside are comparable with those in women taking E(2). E(2)-3beta-glucoside reduces serum gonadotropin levels to the premenopausal range and is effective at reducing postmenopausal symptoms. E(2)-3beta-glucoside is a novel synthetic estrogen that is well tolerated and has promise as a hormone replacement therapy.

P-glycoprotein (P-gp/MDR1)-mediated efflux of sex-steroid hormones and modulation of P-gp expression in vitro.

PURPOSE: To determine whether female sex-steroid hormones and their metabolites can modulate P-glycoprotein (P-gp) expression and catalytic activity and to investigate P-gp mediated transport of these sex-steroids across MDR1-transfected Madine-Darby canine kidney (MDCK) cells. METHODS: Changes in P-gp protein and MDR1 mRNA expression levels were examined in the presence of various estrogens and progestins after a 72-h induction period in the LS180 human colon carcinoma cell line via Western blotting and semiquantitative Reverse-transcription-polymerase chain reaction (RT-PCR), respectively. Concentration-dependent stimulation of vanadate-sensitive P-gp ATPase activity was measured in membranes of Sf9 insect cells infected with a recombinant baculovirus containing the human MDR1 cDNA used with appropriate control membranes. MDCK and MDR1-transfected MDCK cell lines were then used to measure bidirectional P-gp transport of various steroids in the presence and absence of the P-gp inhibitor, GG918. Samples obtained were quantified using LC/MS. RESULTS: Our findings show that P-gp protein levels are inducible by estrone (4-fold over control), estriol (2-fold), and ethynyl estradiol (3-fold). MDR1 mRNA expression levels were also inducible in a concentration-dependent manner from 25 nM to 10 microM. Bidirectional transport studies indicate that ethynyl estradiol, estrone, and estriol are all substrates for P-gp with respective efflux ratios of 10.3, 6.9, and 2.8. Norethindrone was not found to be a substrate for P-gp. Ethynyl estradiol and progesterone were able to significantly stimulate P-gp ATPase activity in a concentration-dependent manner. CONCLUSIONS: Our studies indicate that several sex-steroid hormones are substrates for P-gp-mediated transport and are also able to induce P-gp expression at both the protein and mRNA level in vitro. Stimulation of P-gp ATPase catalytic activity by steroid hormones was also observed, suggesting physical interactions and identifying a need for further investigations to understand the in vivo effects of endogenous and synthetic steroid hormones on the expression and function of P-gp.

Dietary exposure to xenoestrogens in New Zealand.

Continuing evidence of the feminising effects of xenoestrogens on a range of wildlife species increases the need to assess the human health risk of these estrogen mimics. We have estimated the exposure of New Zealand males, females and young men to a range of naturally occurring and synthetic xenoestrogens found in food. Only estrogenic compounds that act by interaction with the estrogen receptor have been included. Theoretical plasma estrogen activity levels were derived from estrogen exposure estimates and estrogenic potency data. Theoretical plasma levels were compared with published data for specific xenoestrogens. There was surprisingly close agreement. Xenoestrogenicity from dietary intake was almost equally attributed to naturally occurring and synthetic xenoestrogens. Relative contributions for a male, for example were isoflavones (genistein and daidzein) (36%) and bisphenol A (34%) with smaller contributions from alkyl phenols (18%) and the flavonoids (phloretin and kaempferol) (12%). It is suggested that dietary xenoestrogens might have a pharmacological effect on New Zealand males and postmenopausal women, but are unlikely to be significant for pre-menopausal women.

The combined contraceptive ring NuvaRing and spermicide co-medication.

The effects of nonoxynol-9 on etonogestrel and ethinylestradiol release and absorption from NuvaRing were studied in 12 subjects for two cycles: one control and one interaction cycle (nonoxynol-9 was administered on day 8). Nonoxynol-9 had no effect on release or absorption and, consequently, serum levels. Therefore, nonoxynol-9 did not compromise the contraceptive efficacy of NuvaRing.

Estrogenic activity of an environmental pollutant, 2-nitrofluorene, after metabolic activation by rat liver microsomes.

In this study, the metabolic activation of 2-nitrofluorene (NF) to estrogenic compounds was examined. NF was negative in estrogen reporter assays using estrogen-responsive yeast and human breast cancer cell line MCF-7. However, the compound exhibited estrogenic activity after incubation with liver microsomes of 3-methylcholanthrene-treated rats in the presence of NADPH. Minor estrogenic activity was observed when liver microsomes of untreated or phenobarbital-treated rats were used instead of those from 3-methylcholanthrene-treated rats. When the compound was incubated with the liver microsomes of 3-methylcholanthrene-treated rats in the presence of NADPH, 7-hydroxy-2-nitrofluorene (7-OH-NF) was formed as a major metabolite. However, little of the metabolite was formed by liver microsomes of untreated or phenobarbital-treated rats. Rat recombinant cytochrome P450 1A1 exhibited a significant oxidase activity toward NF, affording 7-OH-NF. Liver microsomes of phenobarbital-treated rats also enhanced oxidase activity toward NF. In this case, 9-hydroxy-2-nitrofluorene was formed. 7-OH-NF exhibited a significant estrogenic activity, while the activity of 9-hydroxy-2-nitrofluorene was much lower. These results suggest that the estrogenic activity of NF was due to formation of the 7-hydroxylated metabolite by liver microsomes.

The effect of food on the bioavailability of norethindrone and ethinyl estradiol from norethindrone acetate/ethinyl estradiol tablets intended for continuous hormone replacement therapy.

As part of the development of a combination product containing norethindrone acetate and low-dose ethinyl estradiol for continuous hormone replacement therapy in postmenopausal women, a study was conducted to determine the effect of a high-fat meal on the bioavailability of norethindrone and ethinyl estradiol from tablets containing 1 mg norethindrone acetate/10 micrograms ethinyl estradiol. Eighteen healthy postmenopausal women participated in an open-label, single-dose, randomized, three-way crossover study in which 2 x 1/10 norethindrone acetate/ethinyl estradiol tablets were administered fasting and with a high-fat breakfast, and the same dose was administered in solution. Following each treatment, serial blood samples were collected for 48 hours, and plasma ethinyl estradiol and norethindrone concentrations were determined by a validated gas chromatography/mass spectrometry (GC/MS) method. Individual plasma ethinyl estradiol and norethindrone pharmacokinetic parameters were calculated by noncompartmental methods for each treatment and analyzed by ANOVA to obtain differences between least squares treatment mean values and associated 90% confidence intervals. Rates of ethinyl estradiol and norethindrone availability from tablets administered with food were slower than availability rates from tablets administered while fasting. Systemic exposure to ethinyl estradiol was unaffected by administration of tablets with food, whereas exposure to norethindrone increased by 27%. Because administration of norethindrone acetate/ethinyl estradiol 1/10 tablets with a high-fat meal did not decrease systemic exposure to norethindrone and ethinyl estradiol, this formulation can be taken without regard to meals.

Permeability characteristics of endocrine-disrupting chemicals using an in vitro cell culture model, Caco-2 cells.

The purpose of this study was to evaluate the permeability characteristics of endocrine disrupting chemicals utilizing epithelial monolayers of Caco-2 cells. The drugs tested in this study were bisphenol A (BPA), tert-octylphenol (tOP), tert-butylphenol (tBP), di(2-ethylhexyl)phthalate (DOP), dibutylphthalate (DBP), and butylbenzylphthalate (BBP), all of which are used in plastic materials. The Caco-2 cell line was grown on cell culture inserts with polyethylene terephthalate membranes, and Hank's balanced salt solution (HBSS, pH 7.4) was used for the transport experiments. The barrier properties were assessed by measuring transepithelial electrical resistance (TEER) using a volt ohmmeter, and transport of these endocrine disrupting chemicals was examined in both directions. The permeated amounts of these chemicals within 180 min in the apical to basolateral (A-to-B) and the basolateral to apical (B-to-A) directions without verapamil, a P-glycoprotein (P-gp) inhibitor, were in the rank order of tBP > tOP > BPA > DOP > DBP > BBP and BPA >> tBP > tOP > DOP > DBP > BBP, respectively. In the presence of 100 microM verapamil, the permeated amounts of BPA, tOP and tBP within 180 min in the B-to-A direction decreased by 12-, 2.6- and 3.1-fold, respectively. In the case of phthalate esters, the permeated amount of DOP within 180 min in the B-to-A direction decreased by 1.6-fold, while that of DBP and BBP showed no significant changes. The ratios of apparent permeability coefficient of B-to-A against A-to-B, P(app) ratios, for BPA, tOP and tBP were markedly decreased in the presence of 100 microM verapamil. These findings indicated that both BPA and alkyl phenols are substrates of the P-gp located in the apical side of Caco-2 cells, and suggested that the P-gp in the small intestine may act as an organic barrier against BPA and alkyl phenols.

Effect of concomitant hormone replacement therapy containing estradiol and levonorgestrel on the pharmacokinetics of selegiline.

OBJECTIVE: The aim of this study was to investigate the effect of hormone-replacement therapy (HRT) on the pharmacokinetics of the selective monoamine oxidase B inhibitor selegiline and its primary metabolites desmethylselegiline and l-metamphetamine. METHODS: In this randomised, double-blind, cross-over trial, 12 healthy female subjects received once daily for 10 days either HRT containing 2 mg estradiol valerate and 250 microg levonorgestrel or matched placebo. On day 10, they took a single 10-mg oral dose of selegiline. The serum concentrations of selegiline, desmethylselegiline and metamphetamine were measured for 32 h. RESULTS: There was a 59% difference ( P=0.14) in the area under the serum concentration-time curve (AUC) of selegiline during the HRT compared with the placebo phase, but only a little or no concomitant reduction in the AUC of desmethylselegiline (-7%, P=0.071) or metamphetamine (2%, P=0.614) was observed. Maximum plasma concentration (C(max)) of selegiline was not changed, but a small, statistically significant, reduction in the C(max) of desmethylselegiline (-17%, P=0.03) was seen during the HRT phase. The C(max) of methamphetamine was slightly but not significantly reduced (-5%, P=0.06). The unchanged AUC ratios of desmethylselegiline/selegiline and metamphetamine/selegiline indicate that the primary metabolism of selegiline was not affected by HRT. All study treatments were well tolerated. CONCLUSION: Unlike oral contraceptives, HRT is not likely to have clinically significant pharmacokinetic interaction with selegiline.

Distribution and unspecific protein binding of the xenoestrogens bisphenol A and daidzein.

Physiological toxicokinetic (PT) models are used to simulate tissue burdens by chemicals in animals and humans. A prerequisite for a PT model is the knowledge of the chemical's distribution among tissues. This depends on the blood flow and also on the free fraction of the substance and its tissue:blood partition coefficients. In the present study we determined partition coefficients in human tissues at 37 degrees C for the two selected xenoestrogens bisphenol A (BA) and daidzein (DA), and their unspecific binding to human serum proteins. Partition coefficients were obtained by incubating blood containing BA or DA with each of the following tissues: brain, liver, kidney, muscle, fat, placenta, mammary gland, and adrenal gland. Blood samples were analysed by HPLC. For BA and DA, all partition coefficients in non-adipose tissues were similar (average values: BA 1.4, DA 1.2). However, the lipophilic properties of both compounds diverge distinctly. Fat:blood partition coefficients were 3.3 (BA) and 0.3 (DA). These values indicate that with the exception of fat both compounds are distributed almost equally among tissues. In dialysis experiments, the unspecific binding of BA and DA with human serum proteins was measured by HPLC. For BA, the total concentration of binding sites and the apparent dissociation constant were calculated as 2000 and 100 nmol/ml, respectively. Because of the limited solubility of DA, only the ratio of the bound to the free DA concentration could be determined and was found to be 7.2. These values indicate that at low concentrations only small percentages of about 5% (BA) and 12% (DA) are as unbound free fractions in plasma. Since only the unbound fraction can bind to the estrogen receptor, binding to serum proteins represents a mechanism that limits the biological response in target tissues.

Prediction of the bioaccumulation factors and body burden of natural and synthetic estrogens in aquatic organisms in the river systems.

This study undertakes an initial prediction of the bioaccumulation factors and body burden of the steroid estrogens, estrone, estradiol, estriol and ethinylestradiol in a range of aquatic organisms (plankton, benthic and free-living invertebrates and fish) in river systems using a food-web model. These data are compared to that derived from less complex predictions based on octanol-water partition coefficient and molecular connectivity index. The model predicted that bioaccumulation of steroid estrogens occurred in all organisms, however, the values were small, and the maximum and minimum bioaccumulation factors in this study were found in the fish at the lowest trophic level with ethinylestradiol (332) and the fish at the highest trophic level with estriol (1.8), respectively. Moreover, the bioaccumulation factors were sensitive to the metabolic rates of the estrogens in the free living organisms, while the concentration of estrogens in sediment was a significant factor in determining these values in benthic invertebrates. Biomagnification contributed little to the overall bioaccumulation, but the importance increased in fish exposed to ethinylestradiol. The predicted bioaccumulation factors from the food web model were generally smaller than the calculated bioconcentration factors from the simpler octanol-water partition coefficient/molecular connectivity index based estimates. Compared to literature measured data, the predicted values for fish were approximately 1000 times less than the values observed in laboratory tests, while for invertebrates, the modeled values were less than two orders of magnitude below laboratory results. However, the model predicted a similar bioconcentration factor for plankton in relation to experimental data for Chlorella vulgaris for estrone and estriol.

Comparative assessment of endocrine modulators with oestrogenic activity. II. Persistent organochlorine pollutants.

Risk assessments of synthetic chemicals with oestrogen-like activity must take into account the high dietary levels of natural endocrine modulators in food. In view of current regulations of the European Union, a hygiene-based margin of safety (HBMOS) for xeno-oestrogens was defined as a quotient of estimated human daily intakes weighted by relative rodent in vivo potencies of the compounds. Such comparisons of intakes and potencies of natural isoflavones, with short half-lives, with those of polychlorinated organic pollutants (POP) displaying significant toxicokinetic accumulation, deserves the special consideration of toxicokinetics. For slowly accumulating compounds such comparison is much more favourable when based on comparative blood and tissue levels, not on scenarios of daily exposures. Observing these principles, the present communication extends the HBMOS concept to POP, using o,p'-DDT, the oestrogenic component of DDT mixtures, as a prototype. An HBMOS of 137 is derived for o,p'-DDT indicative of a sufficient margin of safety to ensure the absence of risk to human health due to its hormonal action, under exposure conditions now prevailing in Western countries.

Pharmacokinetics of a contraceptive patch (Evra/Ortho Evra) containing norelgestromin and ethinyloestradiol at four application sites.

AIMS: To determine the pharmacokinetic profile of norelgestromin (NGMN) and ethinyloestradiol (EE) following application of the contraceptive patch, Evra/Ortho Evra, at each of four anatomic sites (abdomen, buttock, arm, and torso). METHODS: Thirty-seven healthy, nonpregnant women aged 20-45 years participated in this open-label, four-period crossover study. Subjects were randomized to one of four treatment (site of application) sequences. Each patch was worn for 7 days, with a 1 month washout between treatments. Blood samples were collected before and at various times up to 240 h after application of each patch. Serum samples were assayed for NGMN and EE by validated methods. RESULTS: The serum concentration reference ranges for NGMN and EE are 0.6-1.2 ng ml-1 and 25-75 pg ml-1, respectively, based on studies of the mean Cave of oral norgestimate 250 microg and EE 35 microg. For all application sites, mean concentrations of NGMN and EE remained within these ranges during the 7 day wear period. Absorption of NGMN and EE during patch application on the buttock, arm, and torso was equivalent. Absorption of NGMN and EE during patch application on the abdomen was approximately 20% less than observed for the other three sites, although mean serum concentrations were still within reference ranges. A previous study demonstrated therapeutic equivalence of patches worn on the abdomen vs other sites. CONCLUSIONS: Serum concentrations of NGMN and EE from the contraceptive patch remain within the reference ranges throughout the 7 day wear period, regardless of the site of application (abdomen, buttock, arm, or torso).