Effects of pesticides and related compounds on steroid metabolism and function

Human health risk assessments of organochlorine pesticides in some food crops from Esa-Oke farm settlement, Osun State, Nigeria

Seasonal levels of organochlorine pesticides (OCPs) in yam, cassava, sweet potato and cocoyam samples collected from Esa-Oke Farm Settlement, Osun State, Nigeria were evaluated. Sampling regiment for three sites lasted four months each during the dry and wet seasons. The dried samples were extracted using Soxhlet extractor with dichloromethane (DCM) as the extraction solvent, while the identification and estimation of OCPs in the crop filtrates, after clean-up, were carried out with Gas Chromatography equipped with Time-of-Flight Mass Spectroscopy Detector (GC-TOFMS). Ten OCPs determined in the crops had the overall seasonal mean levels that ranged from 158 ng/g (dieldrin) to 544 ng/g (heptachlor) and the seasonal mean burden per OCP occurred in the order: heptachlor epoxide (518) > heptachlor (447) > p,p'-DDE (431) > dieldrin (349) > chlordane (327) > aldrin (321) > p,p'-DDD (313) > methoxychlor (303) > endosulfan I (287) > p,p'-DDT (284) for wet season while this order was not the same for dry season of the same crop with heptachlor epoxide (415) > p,p'-DDE (373) > aldrin (305) > heptachlor (307) > methoxychlor (288) > chlordane (274) > p,p'-DDT (263) > p,p'-DDD (263) > endosulfan I (260) > dieldrin (246). For all of the OCPs, the estimated daily intake (EDI) and health risk indices (HRI) were significantly higher than the recommended values. Thus, a regular large-scale consumption of crop products from the farm settlement could result in grave public health concern in the course of time.

Enantio-selective molecular dynamics of (±)-o,p-DDT uptake and degradation in water-sediment system

Enantio-selective molecular dynamics of (±)-o,p-DDT uptake and degradation in water-sediment system is described. Both uptake and degradation processes of (-)-o,p-DDT were slightly higher than (+)-o,p-DDT enantiomer. The optimized parameters for uptake were 7.0μgL^-1 concentration of o,p-DDT, 60min contact time, 5.0pH, 6.0gL^-1 amount of reverine sediment and 25°C temperature. The maximum degradation of both (-)- and (+)-o,p-DDT was obtained with 16 days, 0.4μgL^-1 concentration of o,p-DDT, pH 7 and 35°C temperature. Both uptake and degraded process followed first order rate reaction. Thermodynamic parameters indicated exothermic nature of uptake and degradation processes. Both uptake and degradation were slightly higher for (-)-enantiomer in comparison to (+)-enantiomer of o,p-DDT. It was concluded that both uptake and degradation processes are responsible for the removal of o,p-DDT from nature but uptake plays a crucial role. The percentage degradations of (-)- and (+)-o,p-DDT were 30.1 and 29.5, respectively. This study may be useful to manage o,p-DDT contamination of our earth's ecosystem.

Organochlorine Residues and Risk of Breast Cancer

Considerable attention has recently been focused on the possible role of estrogenic compounds as etiologic agents in the development of human breast cancer. This review summarizes data from relevant laboratory and epidemiological studies to assess the hypothesis that exposure to organochlo-rines, and specifically 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT), increases breast cancer risk. Organochlorine compounds, including pesticides such as DDT and industrial compounds such as the polychlorinated biphenyls (PCBs), have had a long history of use. In general, these compounds are characterized by their high lipophilicity and environmental persistence. DDT was widely used in agriculture and public health programs from 1943 to 1972, when it was removed from use in the Western world. DDT is still used, however, in many developing nations. The International Agency for Research on Cancer concluded that there was adequate evidence that DDT was carcinogenic in laboratory animals, yet epidemiological evidence has not been compelling. The estrogenic activity of o, p'-DDT has been well characterized; however, the affinity of estrogen receptors for this compound is very weak and reported to be 1/2,000–1/10,000 that of 17β-estradiol. Epidemiologically, some investigators have reported elevated levels of 1,1-dichloro-2,2-bis(p-chloro-phenyl)ethylene, a DDT metabolite, and PCBs in breast adipose tissue and blood serum taken from breast cancer patients when compared with controls, while others have reported the absence of such an association. While the etiology of breast cancer is not fully understood, it is generally recognized that estrogenic compounds may increase the risk of disease. Contemporary human exposure to DDT and other organochlorines is very limited and would likely play an insignificant role when compared with other sources of exposure, such as estrogen replacement therapy and phytoestrogens in food.

Acute toxicity assessment of N,N-diethyl-m-toluamide (DEET) on the oxygen flux of the dinoflagellate Gymnodinium instriatum

Despite the ubiquitous occurrence of N,N-diethyl-m-toluamide (DEET) in aquatic systems, assessments evaluating the toxicity of DEET on phytoplankton species are summed to a single study on a unicellular green alga. In particular, the toxicological effects of DEET in dinoflagellates are unknown. In this study, we employed the mixotrophic dinoflagellate Gymnodinium instriatum as a study system to evaluate acute effects of DEET on the oxygen flux of laboratory cultures. This study reports an inhibitory reaction model of DEET described by the equation y = 4.99x(0.54), where y represents the percent inhibition of oxygen flux and x represents DEET concentration in mg L(−1) (r(2) = 0.98). Based on this model, the effective concentration of DEET needed to reduce O2 flux by 50% (EC50) for this species was found to be at 72.9 mg L(−1). The reported EC50 is more than five times lower than the EC50 reported previously for the unicellular green algae Chlorella protothecoides. This study raises the question of the potential toxicological effects of DEET in dinoflagellates, in particular those populations inhabiting systems characterized by low water circulation such as enclosed bays and lagoons.

Neonatal exposure to low doses of endosulfan induces implantation failure and disrupts uterine functional differentiation at the pre-implantation period in rats

We investigated whether neonatal exposure to low doses of endosulfan affects fertility and uterine functional differentiation at pre-implantation in rats. Newborn female rats received the vehicle, 0.2 µg/kg/d of diethylstilbestrol (DES), 6 µg/kg/d of endosulfan (Endo6) or 600 µg/kg/d of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5, and 7. On PND90, the rats were mated to evaluate their reproductive performance on gestational day (GD) 19 and their ovarian steroid serum levels, endometrial proliferation and implantation-associated proteins on GD5. DES and endosulfan decreased the pregnancy rate and the number of implantation sites. On GD5, DES and endosulfan did not change the serum levels of 17β-estradiol (E2) and progesterone (P); the endometrial proliferation decreased, which was associated with silencing of Hoxa10 in the Endo600-treated rats. Both doses of endosulfan increased the progesterone receptor (PR) expression, whereas the higher dose led additionally to an increase in estrogen receptor alpha (ERα). In the Endo600-treated rats, the down-regulation of Hoxa10 was associated with a deregulation of the steroid receptor coregulators. Alterations in endometrial proliferation and the endocrine pathway of Hoxa10/steroid receptors/coregulators might be the mechanism of endosulfan-induced implantation failure.

Occurrences and fate of DDT principal isomers/metabolites, DDA, and o,p'-DDD enantiomers in fish, sediment and water at a DDT-impacted Superfund site

In the 1950s and 60s, discharges from a DDT manufacturing plant contaminated a tributary system of the Tennessee River near Huntsville, Alabama, USA. Regulatory action resulted in declaring the area a Superfund site which required remediation and extensive monitoring. Monitoring data collected from 1988, after remediation, through 2011 showed annual decreases approximating first-order decay in concentrations of total DDT and its six principal congeners (p,p'-DDT, o,p'-DDT, p,p'-DDD, o,p'-DDD, p,p'-DDE and o,p'-DDE) in filets from three species of fish. As of 2013, these concentrations met the regulatory requirements of 5 mg/kg or less total DDT for each fish tested. The enantiomer fractions (EF) of chiral o,p'-DDD in smallmouth buffalo and channel catfish were always below 0.5, indicating preferential decay of the (+)-enantiomer of this congener; this EF did not change significantly over 15 years. The often-neglected DDT metabolite p,p'-DDA was found at a concentration of about 20 μg/l in the ecosystem water.

Activated Estrogens and Antiestrogens: A 30-Year Journey with David Kupfer

David Kupfer had a passion for drug metabolism and used his talents to understand the putative metabolic activation of the insecticides o, p'DDT and methoxychlor to estrogens. His research helped to create a scientific foundation for the current interest in endocrine disruption. With the increasing clinical significance of tamoxifen in the late 1980s, and the proposal to test tamoxifen as a breast cancer chemopreventive in healthy women, David initiated laboratory studies on the mechanisms of tamoxifen metabolism. He was the first to note that tamoxifen is metabolically activated to alkylating species. Tamoxifen and insecticides covalently bind to microsomal proteins. His contribution presaged worldwide studies of the induction of rat liver carcinogenesis by tamoxifen.

Organochlorine contamination in the Great Crested Grebe (Podiceps cristatus): effects on eggshell thickness and egg steroid levels

Eggs of the Great Crested Grebe (Podiceps cristatus) were collected from a breeding area on Lake Maggiore (Northern Italy) from 2001 to 2005 in the vicinity of a p,p'-DDT manufacturer, whose production was stopped in 1996. DDT homologue and PCB congener levels were determined and compared to levels in eggs collected from other breeding areas on Lake Maggiore and in a presumably less contaminated area on Lake Garda. Although Lake Garda eggs on average possessed a lower level of p,p'-DDE than Lake Maggiore eggs, they had significantly higher levels of PCBs and could not be used as a reference population for the measurement of eggshell thickness. Nevertheless, a negative linear relationship was found between p,p'-DDE concentration and eggshell thickness for eggs collected from both lakes, indicating a possible causal relationship. Testosterone and 17beta-estradiol concentrations were also determined for eggs collected from both lakes in 2004. Average concentrations of both hormones were the lowest in eggs from Lake Maggiore; however, the very high variability within broods did not result in any significant difference between the lakes.

Influence of organochlorine pesticides on physiological potency of cultured granulosa cells from bovine preovulatory follicles

In the present study the direct effect of Dichlorodiphenyltrichloroethane (DDT), Methoxychlor (MXC) and Hexachlorocyclohexane (gammaHCH) was investigated on the DNA synthesis (measured by [3H]thymidine incorporation); proliferation (determined by colorimetric MTT[3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl tetrazolium bromide] assay); and steroidogenesis (estradiol 17beta, progesterone determination) of granulosa cells during in vitro culture. The cells were aspirated from preovulatory follicles in PMSG-treated heifers. They were cultivated in phenol red and serum (0.1% FCS) RPMI 1640 medium without or with the 3 pesticides in different concentrations. In summary, the results showed differential inhibition of parameters named above by these pesticides (gammaHCH < MXC < DDT) in comparison with vehicle-treated control. Progesterone synthesis was more inhibited than estradiol 17beta production by 3 chemicals, which resulted from the loss of viability of cells indicated by estimation of cell-shape-factor and viability of cells. Besides the inhibitory effect, there was a stimulatory effect of low concentrations of DDT and MXC on [3H]thymidine incorporation and proliferation.

Prediction of estrogen receptor agonists and characterization of associated molecular descriptors by statistical learning methods

Specific estrogen receptor (ER) agonists have been used for hormone replacement therapy, contraception, osteoporosis prevention, and prostate cancer treatment. Some ER agonists and partial-agonists induce cancer and endocrine function disruption. Methods for predicting ER agonists are useful for facilitating drug discovery and chemical safety evaluation. Structure-activity relationships and rule-based decision forest models have been derived for predicting ER binders at impressive accuracies of 87.1-97.6% for ER binders and 80.2-96.0% for ER non-binders. However, these are not designed for identifying ER agonists and they were developed from a subset of known ER binders. This work explored several statistical learning methods (support vector machines, k-nearest neighbor, probabilistic neural network and C4.5 decision tree) for predicting ER agonists from comprehensive set of known ER agonists and other compounds. The corresponding prediction systems were developed and tested by using 243 ER agonists and 463 ER non-agonists, respectively, which are significantly larger in number and structural diversity than those in previous studies. A feature selection method was used for selecting molecular descriptors responsible for distinguishing ER agonists from non-agonists, some of which are consistent with those used in other studies and the findings from X-ray crystallography data. The prediction accuracies of these methods are comparable to those of earlier studies despite the use of significantly more diverse range of compounds. SVM gives the best accuracy of 88.9% for ER agonists and 98.1% for non-agonists. Our study suggests that statistical learning methods such as SVM are potentially useful for facilitating the prediction of ER agonists and for characterizing the molecular descriptors associated with ER agonists.

Abiotic transformation of DDT in aqueous solutions

Significant concentrations of chlorinated pesticides such as 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and its two main transformation products, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE) are still present in soil and sediment systems more than 30 years after DDT use was banned in the United States. DDT enters waterways via the runoff from industrial point sources, agricultural lands and atmospheric deposition. We evaluated zero-valent iron (Fe(0)), ferrous sulfide (FeS), as well as combining them with hydrogen peroxide (H(2)O(2)) as viable treatment technologies for degrading DDT in an aqueous solution. Treatment of DDT with Fe(0) and FeS resulted in approximately 88% and 56% transformation of DDT within 150h, respectively. DDE production was insignificant in all systems. The DDT removal was slower with FeS than with Fe(0), but the amounts of DDD and DDE produced did not exceed baseline. Treatment with a 1:1 mixture of Fe(0)-FeS removed about 95% of the added mass of DDT within 4days and generated significant amounts of DDD and minor amounts of DDMU. When small amounts of H(2)O(2) were introduced halfway through the Fe(0) and FeS treatment times, the mass of DDT decreased by 87% and 96%, respectively, within 2days. Our results demonstrate that mixtures of Fe(0)-FeS in combination with H(2)O(2) can be used for rapid and efficient removal of DDT from aqueous solutions.

David Kupfer: a career retrospective

David Kupfer's research career spanned 50 years and he authored or co-authored over 160 papers and book chapters. Although best known for his work centering on cytochrome P450 metabolism of prostaglandins, steroids, and proestrogenic compounds, David's research also contributed key advances in the areas of P450 induction and catalytic mechanism, breast cancer therapy, and analytical methodology. His research is reviewed here.

Effect of dichlorvos on hepatic and pancreatic glucokinase activity and gene expression, and on insulin mRNA levels

Several studies have shown that organophosphate pesticides affect carbohydrate metabolism and produce hyperglycemia. It has been reported that exposure to the organophosphate pesticide dichlorvos affects glucose homeostasis and decreases liver glycogen content. Glucokinase (EC 2.7.1.1) is a tissue-specific enzyme expressed in liver and in pancreatic beta cells that plays a crucial role in glycogen synthesis and glucose homeostasis. In the present study we analyzed the effect of one or three days of dichlorvos administration [20 mg/kg body weight] on the activity and mRNA levels of hepatic and pancreatic glucokinase as well as on insulin mRNA abundance in the rat. We found that the pesticide affects pancreatic and hepatic glucokinase activity and expression differently. In the liver the pesticide decreased the enzyme activity; on the contrary glucokinase mRNA levels were increased. In contrast, pancreatic glucokinase activity as well as mRNA levels were not affected by the treatment. Insulin mRNA levels were not modified by dichlorvos administration. Our results suggest that the decreased activity of hepatic glucokinase may account for the adverse effects of dichlorvos on glucose metabolism.

Prenatal DDT exposure in relation to anthropometric and pubertal measures in adolescent males

DDT (dichlorodiphenyltrichloroethane), a pesticide once used widely in agriculture and now limited to public health use, remains a controversial chemical because of a combination of benefits and risks. DDT or its breakdown products are ubiquitous in the environment and in humans. Compounds in the DDT family have endocrine actions and have been associated with reproductive toxicity. A previous study reported associations between prenatal exposure to p,p -DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene] and increased height and weight in adolescent boys. We examined a group with higher exposures to see whether similar associations would occur. Our study group was 304 males born in Philadelphia in the early 1960s who had participated in a previous study. Anthropometric and pubertal measures from one to six visits during their adolescent years were available, as were stored maternal serum samples from pregnancy. We measured p,p -DDE, p,p -DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane], and o,p -DDT [1,1,1-trichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl)-ethane] in the maternal serum. Outcomes examined in the boys were height, ratio of sitting height to height, body mass index, triceps skinfold thickness, ratio of subscapular to the sum of triceps and subscapular skinfold thicknesses, skeletal age, serum testosterone, and serum dehydroepiandrosterone sulfate. No associations between prenatal exposure to any of the DDT compounds and any outcome measure were seen.

Liquid chromatographic separation of the enantiomers of trans-chlordane, cis-chlordane, heptachlor, heptachlor epoxide and α-hexachlorocyclohexane with application to small-scale preparative separation

Analytical high-performance liquid chromatographic separations of the individual enantiomers of five polychlorinated compounds were obtained on polysaccharide stereoselective HPLC columns. The enantiomers of the pesticides trans-chlordane, cis-chlordane and heptachlor were separated on CHIRALCEL OD using a hexane mobile phase. The enantiomers of the heptachlor metabolite, heptachlor epoxide, were separated on CHIRALPAK AD using a methanol mobile phase. The enantiomers of alpha-hexachlorocyclohexane (alpha-HCH), were separated on CHIRALCEL OJ using a hexane/2-propanol mobile phase. Similar chromatographic conditions using preparative columns were used to isolate approximately 250 mg of each of the individual enantiomers. The purified individual enantiomers have been submitted for testing of their endocrine disruptor (ED) activity.

The organochlorine o,p'-DDD disrupts the adrenal steroidogenic signaling pathway in rainbow trout (Oncorhynchus mykiss)

The mechanisms of action of o,p'-DDD on adrenal steroidogenesis were investigated in vitro in rainbow trout (Oncorhynchus mykiss). Acute exposures to o,p'-DDD inhibited ACTH-stimulated cortisol secretion while cell viability decreased significantly only at the highest concentration tested (200 microM o,p'-DDD). Stimulation of cortisol secretion with a cAMP analogue (dibutyryl-cAMP) was inhibited at a higher concentration than that needed to inhibit ACTH-stimulated cortisol synthesis in cells exposed to o,p'-DDD. Forskolin-stimulated cortisol secretion and cAMP production, and NaF-stimulated cAMP production were inhibited in a concentration-dependent manner by o,p'-DDD. In contrast, basal cortisol secretion was stimulated while basal cAMP production was unaffected by o,p'-DDD. Pregnenolone-stimulated cortisol secretion was enhanced by o,p'-DDD at a physiologically relevant pregnenolone concentration, while o,p'-DDD inhibited cortisol secretion when a pharmacological concentration of pregnenolone was used. Our results suggest that the cAMP generation step is a target in o,p'-DDD-mediated disruption of ACTH-stimulated adrenal steroidogenesis in rainbow trout but that other downstream targets such as steroidogenic enzymes responsible for cortisol synthesis might also be affected.

Lack of antiandrogenic effects in adult male rats following acute exposure to 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE)

Although the insecticide dichlorodiphenyltrichloroethane (DDT) was banned in the US in 1972, DDT and its major metabolite 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (DDE) are still persistent in the environment. DDE at high doses is antiandrogenic in fetal and adult rats and, therefore, is of concern in humans exposed environmentally. The objective of this work was to determine the dose-response relationship between DDE and its antiandrogenic effect in adult, male rats and to quantitate the concentration of DDE in tissues following oral exposures. Adult, male, Long-Evans rats (11-13 weeks) were castrated, implanted with testosterone capsules, and dosed by oral gavage with 0, 5, 12.5, 25, 50, or 100 mg DDE per kg body weight (BW) per day in corn oil for 4 days. On day 5 the rats were euthanized and liver, adrenals, ventral prostate, and seminal vesicles were weighed as a measure of response to DDE exposure. Blood, adrenals, brain, fat, kidney, lung, liver, muscle, ventral prostate, seminal vesicles, and skin were analyzed for DDE concentrations. Testosterone and dihydrotestosterone were measured in serum. There was a decrease in prostate weight that was not dose dependent; only the prostate weights in rats treated with 12.5 mg DDE per kg BW per day were reduced significantly compared to controls. The liver displayed a dose-dependent increase in weight that was significantly greater than control at DDE doses of 25, 50, and 100 mg/kg BW per day. Blood concentrations of DDE ranged from 0.32 to 11.3 ppm, while tissue concentrations ranged from 0.72 to 2620 ppm with the highest concentration in fat. Although DDE concentrations in the androgen-responsive tissues were higher than concentrations previously shown in vitro to inhibit androgen-receptor transcriptional activity, these concentrations did not appear to be antiandrogenic in vivo. The doses administered to the rats in this study are at least 10(5)-fold greater than the daily, average of human dietary intake of DDE.

Determination of chiral ratio of o,p-DDT and o,p-DDD pesticides on polysaccharides chiral stationary phases by HPLC under reversed-phase mode

A simple and reliable HPLC method for the chiral resolution of o,p-DDT and o,p-DDD is described. The enantiomeric resolution of o,p-DDT and o,p-DDD has been achieved on Chiralpak AD-R, Chiralcel OD-R, and Chiralcel OJ-R chiral stationary phases. The mobile phases used were acetonitrile-water (50:50 [v/v]) and acetonitrile-2-propanol (50:50 [v/v]) at a flow rate of 1.0 mL/min. For both pesticides detection was done at 220 nm. The values for o,p-DDT of alpha and R(s) varied from 1.24 to 2.52 and from 0.80 to 2.47, respectively. The values of alpha and R(s) for o,p-DDD were 1.26 and 0.60, respectively.

The turnover of phospholipid fatty acyl chains is activated by the insecticide Dieldrin in Bufo arenarum oocytes

Dieldrin is a widespread environmental contaminant hazardous to many wildlife species. Some evidence obtained with Bufo arenarum oocytes indicates that Dieldrin decreases the fertilization rate in amphibian oocytes, but little is known about mechanisms by which the pesticide affects fertilization. Therefore, we investigated the effect of Dieldrin on oocyte phospholipid metabolism. Freshly obtained oocytes, prelabeled with 2 3H-glycerol or 9-10 3H palmitate, were exposed to 4 mg/L Dieldrin for 2 hours. Dieldrin reduced the amount of 2 3H-glycerol incorporation in all phosphoglycerides classes: PI, PA, PS, and SPH were affected in 80% of the cases and PC and PE were only reduced in 39% of the cases. The incorporation in neutral lipids was not affected. On the contrary, 9,10 3H-palmitate incorporation increased in PC, PI, and PA, but TAG and FFA decreased. The more efficient incorporation of 3H-palmitate compared with 3H-glycerol in Dieldrin-treated oocytes suggests the operation of an alternative route other than de novo synthesis for phospholipids. The retailoring of phosphoglycerides via a deacylation-acylation pathway was demonstrated. These changes in phospholipid metabolism could be associated with the activation of certain enzymes produced by the pesticide.

Pubertal growth and development and prenatal and lactational exposure to polychlorinated biphenyls and dichlorodiphenyl dichloroethene

OBJECTIVES

Polychlorinated biphenyls (PCBs) and dichlorodiphenyl dichloroethene (DDE) are ubiquitous toxic environmental contaminants. Prenatal and early life exposures affect pubertal events in experimental animals. We studied whether prenatal or lactational exposures to background levels of PCBs or DDE were associated with altered pubertal growth and development in humans.

STUDY DESIGN

Follow-up of 594 children from an existing North Carolina cohort whose prenatal and lactational exposures had previously been measured. Height, weight, and stage of pubertal development were assessed through annual mail questionnaires.

RESULTS

Height of boys at puberty increased with transplacental exposure to DDE, as did weight adjusted for height; adjusted means for those with the highest exposures (maternal concentration 4+ ppm fat) were 6.3 cm taller and 6.9 kg larger than those with the lowest (0 to 1 ppm). There was no effect on the ages at which pubertal stages were attained. Lactational exposures to DDE had no apparent effects; neither did transplacental or lactational exposure to PCBs. Girls with the highest transplacental PCB exposures were heavier for their heights than other girls by 5.4 kg, but differences were significant only if the analysis was restricted to white girls.

CONCLUSIONS

Prenatal exposures at background levels may affect body size at puberty.

Inhibitory effects of organochlorine pesticides on intercellular transfer of Lucifer Yellow in cultured bovine oviductal cells

The present study investigated the effects of dichlorodiphenyltrichloroethane (DDT), methoxychlor (MXC), and gamma-hexachlorocyclohexane (gammaHCH, lindane) on gap junctional intercellular communication (GJIC) in cultured bovine oviductal cells. GJIC was evaluated by microinjecting fluorescent dye Lucifer Yellow and observing the inhibition of the spreading of dye into adjacent cells. After incubation for 1 h at 37 degrees C, a dose-dependent inhibition of GJIC was observed over a concentration range of 16 to 128 microM DDT, MXC, or gammaHCH compared with nonexposed controls. A significant inhibition began at 32 microM DDT, MXC, or gammaHCH. After incubation for 5 h, a dose-dependent inhibition of GJIC was obtained in the concentration range from 8 to 64 microM of the pesticides. The first significant inhibitory effect on GJIC was caused by 8 microM DDT, 16 microM MXC, and 32 microM gammaHCH. The 128 microM concentration of the pesticides was toxic. At pesticide concentration of 64 microM, the decrease in dye-coupling observed was not due to lethal cell injury, as is indicated by the use of trypan blue dye exclusion. After removal of 64 microM DDT from the culture medium, intercellular communication was reestablished within 3 h. Measurement of cytosolic free Ca2+ concentration [Ca2+]i in fura-2/AM-loaded oviductal cells showed that the inhibition of GJIC by addition of DDT, MXC, or gammaHCH was not associated with a detectable increase in [Ca2+]i. Coincubation of the DDT with dibutyryl-cAMP prevented the 64 microM DDT-induced inhibition of intercellular communication in adherent oviduct cells. It is suggested that organochlorine pesticides can influence cells responsible for reproduction.

Influence of organochlorine pesticides on transmembrane potential, oxidative activity, and ATP-induced calcium release in cultured bovine oviductal cells

The present study investigated the effects of the pesticides DDT, MXC, and gammaHCH on transmembrane potential, oxidative activity, cytotoxicity and ATP-induced intracellular Ca2+ release in cultured bovine oviductal cells. Transmembrane potential, oxidative activity, and cytotoxicity were assessed using the fluorescent dyes bis-oxonol, dihydrorhodamine 123, and propidium iodide (PI), respectively, and measured spectrofluorometrically in a microplate reader. The cultured cells were loaded with Ca2+-sensitive fluorochrome fura-2-AM, and cytosolic free calcium ([Ca2+]i) was monitored by a microscope image analysis system. A dose-dependent increase in depolarization and changes of oxidative activity were observed over a concentration range of 8 to 128 microM DDT and MXC compared to nonexposed controls. At a concentration of 16 microM DDT or MXC, the oxidative activity and depolarization of cells were significantly enhanced compared to controls, but most of the cells were intact as indicated by the fact that PI-staining was not significantly increased. Trypan-blue staining indicated that the viability of oviductal cells decreased significantly when exposed to concentrations of 64 and 128 microM DDT or MXC. ATP-mediated enhancement of [Ca2+]i in cells was almost completely inhibited after incubation with 128 microM DDT for 3 h at 37 degrees C. This response was reduced to approximately 50% after incubation of the cells with MXC at 128 microM; lindane did not significantly interfere with the above physiologic parameters.

Methoxychlor as a model for environmental estrogens

Estrogens can have a variety of physiological effects, especially on the reproductive system. Chemicals with estrogenic activity that are present in the environment may thus be considered potentially hazardous to development and/or reproduction. Methoxychlor is one such chemical, a chlorinated hydrocarbon pesticide with proestrogenic activity. Metabolism of the chemical either in vivo or using liver microsomes produces 2,2-bis(p-hydroxyphenyl)- 1,1,1-trichloroethane (HPTE), the active estrogenic form, and the delineation of this mechanism is reviewed herein. When administered in vivo, methoxychlor has adverse effects on fertility, early pregnancy, and in utero development in females as well as adverse effects on adult males such as altered social behavior following prenatal exposure to methoxychlor. Effects of methoxychlor on the female have been studied extensively, whereas reports on the chemical's effects on males are less common. From the studies reviewed here, the reproductive toxicity of methoxychlor is evident, but the significance of this toxicity with respect to human health remains to be determined.

Occupational exposures and risk of female infertility

This study examined the association between occupational chemical and radiation exposures and risk of medically diagnosed infertility in 281 women compared with 216 fertile women. After adjustment for age and exposures that occurred before case/referent ascertainment, there was an increased risk of infertility among those women exposed to volatile organic solvents (odds ratio [OR], 1.74; 95% confidence interval [CI], 1.11 to 2.71), chemical dusts (OR, 2.66; CI, 1.17 to 6.05), pesticides (OR, 3.02; CI, 1.10 to 8.29), and video display terminals (OR, 2.21, CI, 1.22, to 4.01). Among the medically diagnosed causes of infertility, the adjusted risk associated with having an ovulatory factor increased among those women exposed to solvents (OR, 1.75; CI, 1.03 to 2.98), dusts (OR, 3.00; CI, 1.19 to 7.52), or pesticides (OR, 3.82; 1.28 to 11.42). Solvents and dusts also were associated with a higher risk of tubal-factor infertility (solvents; OR, 1.95; CI, 1.08 to 3.52; dusts: OR, 2.87; CI, 1.05 to 7.88) and endometriosis (solvents: OR, 2.13; CI, 0.96 to 4.72; dusts: OR, 3.63; CI, 0.99 to 13.28). Video display terminal exposure was more likely to be found among those women diagnosed with endometriosis (OR, 3.69; CI, 1.50 to 9.13) and cervical-factor infertility (OR, 2.65; CI, 0.99 to 7.12). Results suggest that among women with a medically confirmed diagnosis, fertility may be adversely affected by a variety of occupational chemical exposures.

Dieldrin modifies the hydrolysis of PIP2 and decreases the fertilization rate in Bufo arenarum oocytes

Carbachol treatment in Bufo arenarum oocytes decreases the radioactivity in [32P]PIP2 in the following 20 min after stimulation and increases the [3H]glycerol labeling of 1,2-DAG at 1 min of stimulation. On the contrary, in Dieldrin treated oocytes carbachol stimulation produces an increase in [32P]PIP2 labeling without changes in [3H]1,2-DAG radioactivity. The sustained hydrolysis of PIP2 observed in Control oocytes is necessary to generate the intracellular second messengers which initiate the fertilization pathway. The lack of response to muscarinic stimulation in Dieldrin treated oocytes, may be associated with an early activation of PIP2-PLC by the insecticide, producing a depletion of the PIP2 pool previous to the stimulation with carbachol. These changes take place simultaneously with a decrease in the ability of Bufo arenarum oocytes to be fertilized in vitro, suggesting a correlation between impairment in the PIP2 cascade and a decrease in the fertilization rate.

Persistent DDT metabolite p,p'-DDE is a potent androgen receptor antagonist

The increase in the number of reports of abnormalities in male sex development in wildlife and humans coincided with the introduction of 'oestrogenic' chemicals such as DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) into the environment. Although these phenotypic alterations are thought to be mediated by the oestrogen receptor, they are also consistent with inhibition of androgen receptor-mediated events. Here we report that the major and persistent DDT metabolite, p,p'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene), has little ability to bind the oestrogen receptor, but inhibits androgen binding to the androgen receptor, androgen-induced transcriptional activity, and androgen action in developing, pubertal and adult male rats. The results suggest that abnormalities in male sex development induced by p,p'-DDE and related environmental chemicals may be mediated at the level of the androgen receptor.

Carcinogens in Israeli milk: a study in regulatory failure

The potential danger to humans of exposure to chemicals shown to be carcinogenic in animals has become increasingly clear in the last 20 years. A gap still exists, however, between the appreciation of the risk by scientists and the willingness of public health authorities to reduce it. Three pesticides, shown repeatedly to produce over a dozen different types of cancer in rats and mice, were discovered in inordinately high concentrations in Israeli milk and dairy products. The three pesticides--alpha-BHC, gamma-BHC (lindane), and DDT--had been shown to be present for ten years or more at mean concentrations up to 100 times those found in U.S. dairy products--with resultant concentrations in breast milk being possibly 800 times greater than those in the United States--yet neither the Ministry of Health nor the Israel Cancer Association made any apparent moves either to warn the public or to rectify the situation. A small consumer organization, Consumer Shield, brought the issue into the open. Through public pressure, court action, and the threat of further legal redress--and despite repeated attacks in the media by the milk producers, the Ministry, and the Cancer Association--Consumer Shield forced the authorities to outlaw the use of alpha-BHC and lindane (DDT no longer being in general use). The ban resulted in a precipitous drop in the concentrations of these substances in Israeli milk. Recent epidemiological and laboratory findings suggest that the dramatic drop in breast cancer mortality rates subsequent to the pesticide ban could be a direct result of that ban.

Reproductive toxicity: male and female reproductive systems as targets for chemical injury

On the basis of current knowledge of reproductive biology and toxicology, it is apparent that chemicals affecting reproduction may elicit their effects at a number of sites in both the male and the female reproductive system. This multiplicity of targets is attributable to the dynamic nature of the reproductive system, in which the hypothalamic-pituitary-gonadal axis is controlled by precise positive and negative feedback mechanisms among its components. Interference by a xenobiotic at any level in either the male or the female reproductive system may ultimately impair hypothalamic or pituitary function. Normal gonadal processes such as spermatogenesis or oogenesis, ejaculation or ovulation, hormone production by Leydig or granulosa cells, and the structure or function of the accessory reproductive structures (e.g., epididymis, fallopian tube) also appear vulnerable to xenobiotics. The reproductive system is a complex one that requires local and circulating hormones for control. This brief review illustrates a system for characterizing the mechanism of action of reproductive toxicants, as well as for defining the sites available for disruption of reproduction. Unfortunately, at present, data addressing the actual vulnerability of reproduction are sorely lacking. However, when experiments have been conducted and combined with epidemiologic data or clinical observation, it has been possible to demonstrate impairment of reproductive processes by xenobiotics. The role of environmental exposure to xenobiotics in the increase in infertility that has been observed remains to be defined.

The mechanisms of action of reproductive toxicants

Successful human reproduction is a complex process which requires normal function of 2 individuals. Reproductive toxicants can impair reproduction by acting in the male, female or both. Reproductive toxicants can produce their adverse effects by several direct and indirect mechanisms. The mechanisms by which reproductive toxicants impair reproduction are reviewed.

Sexual behavior of intact female rats after treatment with o,p'-DDT or p,p'-DDT

Sexual behavior of adult, female rats was tested following treatment with o,p'-DDT or with p,p'-DDT during either diestrus or proestrus. Both chlorinated compounds decreased lordosis behavior, but o,p'-DDT did so only after treatment on diestrus. p,p'-DDT in contrast, decreased sexual behavior under all treatment conditions. o,p'-DDT may have altered behavior by disrupting the estrous cycle while p,p'-DDT had a major effect on the female's proceptivity and receptivity without modifying vaginal cyclicity. p,p'-DDT disrupted sexual behavior at doses as low as 25 mg/kg while 100 to 200 mg/kg o,p'-DDT were required. Since commercially prepared DDT contained a predominant proportion of p,p'-DDT, these results suggest that many reproductive effects of DDT may have resulted from p,p'-DDT rather than from o,p'-DDT.

The levo enantiomer of o,p'-DDT inhibits the binding of 17 beta-estradiol to the estrogen receptor

It has been discovered previously that the known estrogenic activity of o,p'-DDT resides with the levo enantiomer. Since it has been presumed that this relatively weak estrogenic activity of o,p'-DDT is mediated by the estrogen receptor, the ability of the resolved enantiomeric forms of o,p'-DDT to inhibit the binding of 17 beta-estradiol to the receptor was investigated. Competitive binding assays including the use of double-reciprocal plots and sucrose gradient analyses revealed that the levo and not the dextro enantiomer could inhibit the estradiol binding to the estrogen receptor. Thus the in vivo estrogenic activity of levo o,p'-DDT correlates with its apparent ability to interact with the estrogen receptor.

Human placental Ca2+-ATPase: in vitro inhibition by DDT homologs

In vitro inhibition of Ca2+-ATPase by DDT homologs was studied using maternal brush-border membranes from human term placentas as an enzyme source. At 10 microM concentration many of the compounds tested inhibited this enzyme. The order of effectiveness of inhibition was as follows: p,p'-DDE greater than p,p'-DDD greater than p,p'-DDT greater than methoxychlor(mec). Both p,p'-DDOH and p,p'-DDA did not inhibit the placental Ca2+-ATPase. Assays using varying concentrations (0.3 microM to 0.1 mM) of p,p'-DDT were also performed. The inhibition of human placental Ca2+-ATPase ranged from 12% for 0.3 microM p,p'-DDT to 69% for 30 microM p,p'-DDT. Higher concentrations of this pesticide failed to cause further enzyme inhibition.

Evaluation of long-term consequences in behavioral and/or neural function following neonatal chlordecone exposure

The effects of neonatal exposure of rats to chlordecone, during the major postnatal period of neuroendocrine differentiation were assessed after the animals matured to 90 days of age. On day 4 postpartum, pups received a s.c. injection of either DMSO vehicle or chlordecone (1 mg/pup) dissolved in DMSO. The neonatal exposure produced a significant sex-dependent alteration in adult body weight; chlordecone-exposed males were lighter than vehicle-exposed controls and chlordecone-exposed females were heavier than vehicle-exposed controls. Behavioral tests sensitive to neonatal chlordecone exposure during preweaning development--i.e., spectral analysis of movement, activity, and auditory startle responsiveness--gave no statistically significant evidence for residual effects of the early organochlorine treatment. When challenged with harmine, a known tremorogen with putative effects on olivocerebellar pathways, chlordecone-exposed males were less responsive than vehicle-exposed littermates in a spectral analysis of movement. The movement spectrum of chlordecone-exposed females was not differentially sensitive to the harmine challenge. However, subsequent evaluation of the auditory startle reflex indicated that harmine interacted with the neonatal treatment and sex of the animal; chlordecone-exposed males were less responsive and chlordecone-exposed females more responsive than same sex vehicle-exposed littermates. The responsiveness to a d-amphetamine challenge, expressed as a ratio of baseline activity in a pre- and post-test design, suggested the chlordecone-exposed males gave an exaggerated response to the drug challenge. Collectively, these findings suggest that the neonatal chlordecone exposure had a significant organizational effect on the development of behavioral and/or neural function. These findings also suggest the predictive utility of early behavioral tests; that is, long-term alterations were noted in each component of the toxicological syndrome previously identified during preweaning development.

Effects of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) on gonadal development in the chick embryo: a histological and histochemical study

Fertile white Leghorn chicken eggs were exposed via intravitelline injections to dosages of 5.0, 10.0, or 20 mg 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) in olive oil prior to incubation. Control embryos received only the olive oil vehicle. Eggs were placed in a forced-draft incubator for either 5 or 12 days. Embryos were removed and their gonadal areas prepared for histological or histochemical evaluation. Histological examination of DDT-exposed 5-day embryos revealed no significant differences in the number of primordial germ cells aggregating in the gonadal area and in the localization of acid and alkaline phosphatase activity. Embryos exposed to DDT for 12 days revealed significant alterations in both ovaries and testes. The testes of DDT-exposed embryos consisted of mostly stroma with fewer seminiferous cords than controls while ovaries of exposed embryos contained a larger number of distended medullary cords as well as a difference in the distribution of these cords when compared to controls. There was an increased alkaline phosphatase activity in the stromal cells of female gonads. Increased amounts of alkaline phosphatase activity found in the stroma at 12 days might be due to a DDT-induced stimulation of these cells to differentiate more rapidly. Acid phosphatase activity was found in the secondary sex cords of control 12-day ovaries, but was much reduced or absent in those of pesticide-exposed embryos. These results indicate that a single dosage of DDT administered to a chick embryo prior to incubation does not affect early stages of gonadal development but that effects on both ovaries and testes occur 12 days following exposure.

Avian endocrine responses to environmental pollutants

Many environmental contaminants are hazardous to populations of wild birds. Chlorinated hydrocarbon pesticides and industrial pollutants are thought to be responsible for population declines of several species of predatory birds through eggshell thinning. Studies have demonstrated that these contaminants have estrogenic potency and may affect the functioning of the gonadal and thyroidal endocrine subsystems. Petroleum crude oil exerts toxicity externally, by oiling of plumage, and internally, by way of ingestion of oil while feeding or preening. Extensive ultrastructural damage to the inner zone of the adrenal, diminished adrenal responsiveness to adrenocorticotrophic hormone, and reduced corticosterone secretion rate suggest that low levels of plasma corticosterone reflect a direct effect of petroleum on the adrenal gland. Suppressive effects of oil on the ovary and decreases in circulating prolactin have been associated with impaired reproductive function. Large-scale field studies of free-living seabirds have confirmed some of the inhibitory effects of oil on reproduction that have been observed in laboratory studies. Organophosphorus insecticides, representing the most widely used class of pesticides in North America, have been shown to impair reproductive function, possibly by altering secretion of luteinizing hormone and progesterone. Relevant areas of future research on the effects of contaminants on avian endocrine function are discussed.

The estrogenic activity of DDT: the in vitro induction of an estrogen-inducible protein by o,p'-DDT

Induced protein is a commonly measured marker for estrogenic action. The induction of induced protein by o,p'-DDT was studied in an in vitro system. Nuclear levels of estrogen receptor translocated by o,p'-DDT correlated highly with induced protein induction, and the time course for induced protein induction was consistent with an estrogen receptor-mediated mechanism. While the maximum amount of induced protein produced by o,p'-DDT was less than after 17 beta-estradiol exposure, the induced protein formed by each compound was indistinguishable on nondenaturing and denaturing polyacrylamide gels. Also, it was shown that o,p'-DDT does not cause additional induction of induced protein over that seen with maximum levels of 17 beta-estradiol, further supporting the premise that these compounds share a common pathway in stimulating the synthesis of induced protein.

Induction by carrot allelochemicals of insecticide-metabolising enzymes in the southern armyworm (Spodoptera eridania)

Carrot foliage monoterpenes induce cytochrome P-450 up to 2.9-fold, NADPH cytochrome c (P-450) reductase up to 1.6-fold, NADPH-oxidation up to 3.8-fold, aldrin epoxidation up to 1.5-fold in southern armyworm larval midgut tissues when incorporated in their diet at 0.2% for 3 days. Stigmasterol and ergosterol did not substantially induce microsomal oxidase activities and significantly inhibited GSH S-aryltransferase activity and sulfotransferase activity. Coumarin did not substantially affect microsomal oxidase and sulfotransferase activity but is the most potent inducer of GSH S-aryltransferase activity, increasing this activity 7-fold. None of the chemicals is acutely toxic to the sixth instar larvae or affect the larval weight gain except coumarin which significantly depressed the maximal body weight attained.

Effect of xenobiotic estrogens and structurally related compounds on 2-hydroxylation of estradiol and on other monooxygenase activities in rat liver

Previous study demonstrated that the administration for several days of 1-(o-chlorphenyl)-1-(p-chlorophenyl)-2,2,2-trichloroethane (o,p'DDT) (estrogenic DDT derivative) or of tamoxifen (antiestrogen), but not of 2,2-bis-(p-chlorophenyl)-1,1-dichloroethylene (p,p'DDE) (nonestrogen), to ovariectomized female rats dramatically diminished the induction of uterine ornithine decarboxylase (ODC) by subsequently administered estradiol [W. H. Bulger and D. Kupfer, Archs Biochem, Biophys. 182, 138 (1977)]. The present investigation examines whether the inhibition of ODC induction by o,p'DDT and tamoxifen may have been due to enhanced hydroxylation of estradiol by the hepatic monooxygenase system. Additionally, the effects of other estrogenic and nonestrogenic xenobiotics on the major route of estradiol metabolism (2-hydroxylation) were examined. Treatment of ovariectomized (ovex) rats with o,p'DDT or p,p'DDE caused induction of hepatic estradiol-2-hydroxylation and increased demethylase activities of several substrates. Administration of Kepone (estrogenic) and Mirex (nonestrogenic), both inducers of hepatic monooxygenase, also increased 2-hydroxylation of estradiol. For comparative purposes, the effects on estradiol-2-hydroxylation of administration of classical estrogens (estradiol and diethylstilbestrol) and antiestrogen (tamoxifen) and inducers of monooxygenase activity (phenobarbital and 3-methylcholanthrene) were also studied. Treatment of ovariectomized and adrenalectomized (ovex/adx) or intact female rats with estradiol or ovex/adx animals with diethylstilbestrol had no effect on estradiol-2-hydroxylation. Similarly, tamoxifen did not alter the rate of estradiol-2-hydroxylation. The treatment of ovex/adx rats with 3-methylcholanthrene did not affect the rate of estradiol-2-hydroxylation. By contrast, ovex/adx female or intact male rats treated with phenobarbital exhibited induction of estradiol-2-hydroxylase activity. In the above studies only 2-hydroxyestradiol was found; there was no evidence for the formation of primary metabolites hydroxylated at other sites on estradiol. The current findings exclude the possibility that the previously observed inhibition of estradiol-mediated induction of ODC by pretreatment with o,p'DDT or tamoxifen (see article cited above) was due to enhanced hydroxylation of estradiol by liver monooxygenases. Also, it was concluded that there is no correlation between the ability to induce hepatic microsomal estradiol-2-hydroxylase activity and estrogenic (or antiestrogenic) properties of a given compound.

Involvement of glucocorticoids in the development of the secondary palate

Genetic differences between various inbred strains of mice in the levels of glucocorticoid receptors embryonic in maxillary mesenchyme cells appear to be reflected in the magnitude of the responses to steroids in these cells. High levels of glucocorticoids cause significant growth inhibition in maxillary mesenchyme cells with subsequent alterations in the production of extracellular matrix components. The presence of higher levels of cytoplasmic glucocorticoid receptor proteins may be one factor which could predispose those strains such as A/J to a greater inhibition of craniofacial growth in vivo by glucocorticoids and therefore increase the frequency of cleft palate production. Furthermore, women with infertility treated with glucocorticoids to support pregnancy give birth to infants with a marked decrease in birth weight [98]. Pharmacologic doses of glucocorticoids can also cause a dramatic reduction in the growth of a number of fetal tissues in mice and humans. In fact, there is evidence that glucocorticoids may be a causative factor in the production of cleft palate in primates [52]. The nature of the molecular elements which determine the biochemical and physiologic responses to glucocorticoids in the palate still remains largely unknown. Although in the mouse there is some evidence to suggest that the major histocompatibility locus (H-2) might be involved, the level(s) at which this control is exerted is unknown. It is possible that this locus may regulate in some manner the level of glucocorticoid receptors and the response to glucocorticoids in the secondary palate. Moreover, there is evidence to suggest that other genes distinct from, but closely linked to the H-2 locus may be important in determining both the strain-dependent differences in susceptibility to glucocorticoid-induced cleft palate and the intracellular levels of cyclic AMP in the secondary palate. It is also apparent that glucocorticoids in conjunction with other hormones or growth factors such as epidermal growth factor and agents which regulate cyclic nucleotide metabolism are essential for the normal development of the secondary palate. Excesses or deficiencies in either the level of these growth regulators and/or in their receptors in specific fetal tissues at defined periods in development are likely to lead to certain fetal malformations. Definition and integration of the genetic, biochemical, and endocrine factors which are involved in the control of cellular growth as influenced by alterations in the composition of cell surface and extracellular matrix components should provide some insights into the events associated with normal palatogenesis.