Doses Of Methoxychlor Research Articles

LACTATIONAL EXPOSURE OF METHOXYCHLOR IMPAIRS SPERM QUALITY IN BALB/C MICE

Numerous pesticides derived from human activity are now disseminated in the environment that have been identified as an estrogenic activity that mainly affects the male reproductive system. The objective study was to determine the dose of methoxychlor (MXC) pesticides administered to the mother during the lactation period that would affect the sperm quality of the offspring in mice. Twenty-four BALB/c strains were divided into control and treatment groups. MXC was administered once daily by intraperitoneal to female mice for days 1 to 21 of lactation periods, with 0.14 mg/g, 0.28 mg/g, and 0,42 mg/g doses of MXC. Male litters were killed at postnatal day (PND) 60, and the cauda epididymis was used to observe sperm motility and morphology characteristics. Parameters observed were the number of spermatozoa abnormal and the percentage of progressive spermatozoa. ANOVA showed that the effect of MXC was significantly different in the case of the number of abnormal sperm and the rate of progressive sperm parameters. Duncan's Multiple Range Test (DMRT) showed that D3 (0.42 mg/g) gave the highest effect of MXC on increasing abnormal spermatozoa morphology and decreasing the percentage of motile sperm. These results indicate that exposure to MXC, which showed a physiological response in the lactation period, reduces the sperm quality of offspring

Ameliorating potentials of N-acetyl-l-cysteine against methoxychlor instigated modulation in structural characteristics of granulosa cells of caprine antral follicles

Follicular granulosa cells (GCs) form an important association with follicle’s survival and health that determines ovulation. Apoptosis induction in GCs leads to follicular atresia and infertility problems. The present study aims at assessing the ultrastructural toxicity of methoxychlor (MXC), an organochlorine insecticide and reproductive toxin, on structural aspects of GCs owing to its potential for inducing apoptosis and the ameliorating potential of N-acetyl-L-cysteine (NAC) in this toxicity. The ultrastructural morphology revealed MXC induced degenerative changes in GCs like loss of cellular junction complexes and membrane integrity; nuclear abnormalities like occurrence of condensed and marginated chromatin, crescent shaped or blebbed nucleus; presence of disrupted mitochondria with disrupted cristae, vacuolization, empty spaces, large number of homogenous lipid droplets and extensive network of rough endoplasmic reticulum and several cytoplasmic processes at various doses of MXC with maximum degeneration observed at 100 µg/mL. NAC supplementation reduced the observed apoptotic characteristics of GCs with most significant changes at 5 and 10 mM concentration. Thus, it is evident that MXC acts as an apoptotic inducer in GCs that influences the quality of antral follicles in mammals; however, NAC, with its anti-oxidative and anti-inflammatory properties, turns out to be a potential therapeutic and anti-apoptotic agent against MXC toxicity.

Ovarian follicle resilience in mice orally dosed with methoxychlor: Are reproductive impacts possible in mammals as ecological receptors?

Abstract Mammals are routinely evaluated with chemical exposure modeling in ecological risk assessments for contaminated terrestrial properties, such as sites managed under the U.S. EPA’s Superfund program. Despite modeling outcomes frequently indicating that site mammals are experiencing severe reproductive impacts, there are virtually no known instances of site mammal populations being either unhealthful or reduced in size. This observation has triggered the development of the one-time patented and recently ASTM International-certified Rodent Sperm Analysis method that directly assesses male reproductive health, and thereby the overall health of mammals that occur at sites. Just as experimentation has led to an understanding of the degree of sperm count reduction, sperm motility reduction, and increase in morphologically altered sperm that need occur for reproduction to be impacted, the degree of ovarian follicle count reduction to similarly impact reproductive success should be able to be determined. Thus, adult female CD-1 mice were orally exposed to vehicle control or methoxychlor at 32 and 64 mg/kg/day for 30 days. Pursuant to resting periods of 30 and 60 days post-dosing, half of the treated animals were euthanized and their ovaries were collected and subjected to histological evaluations of follicle numbers and health. The other half of the animals were mated to proven breeder males to enable evaluation of breeding success. At 30 days post-dosing, primary and pre-antral follicle numbers were increased at both methoxychlor doses compared to controls. Further, the number of atretic follicles nearly doubled at both methoxychlor doses compared to controls. In contrast, at 60 days post-dosing, follicle numbers did not differ between methoxychlor treatment and control groups. These results were corroborated by 60-day mated and non-mated mice displaying an increase in serum anti-Mullerian hormone level, a recognized marker for the quantitative aspect of ovarian reserve. At both 30 day and 60 days post-dosing, pup weights and litter sizes in methoxychlor exposed animals were the same as those of controls. Collectively, these data indicate that oral exposure to methoxychlor did not increase follicle atresia or reduce follicle numbers enough to compromise female fertility. These outcomes may be indicators of ovarian follicle resiliency to chemical exposure, a capability that could benefit mammals in the wild. Ovarian follicle resiliency could, in part, explain the recurrent discovery at contaminated terrestrial sites, of rodent populations that are identical (in terms of size, sex ratio, and age distribution) to those of nearby (non-contaminated) reference locations.

Perinatal exposure to low-dose methoxychlor impairs testicular development in C57BL/6 mice.

Methoxychlor (MXC), an organochlorine pesticide, has adverse effects on male reproduction at toxicological doses. Humans and wild animals are exposed to MXC mostly through contaminated dietary intake. Higher concentrations of MXC have been found in human milk, raising the demand for the risk assessment of offspring after maternal exposure to low doses of MXC. In this study, pregnant mice (F0) were given intraperitoneal daily evening injections of 1 mg/kg/d MXC during their gestational (embryonic day 0.5, E0.5) and lactational periods (postnatal day 21.5, P21.5), and the F1 males were assessed. F1 testes were collected at P0.5, P21.5 and P45.5. Maternal exposure to MXC disturbed the testicular development. Serum testosterone levels decreased, whereas estradiol levels increased. To understand the molecular mechanisms of exposure to MXC in male reproduction, the F1 testes were examined for changes in the expression of steroidogenesis- and spermatogenesis- related genes. RT-PCR analysis demonstrated that MXC significantly decreased Cyp11a1 and increased Cyp19a1; furthermore, it downregulated certain spermatogenic genes (Dazl, Boll, Rarg, Stra8 and Cyclin-a1). In summary, perinatal exposure to low-dose MXC disturbs the testicular development in mice. This animal study of exposure to low-dose MXC in F1 males suggests similar dysfunctional effects on male reproduction in humans.

The ameliorative effect of propolis against methoxychlor induced ovarian toxicity in rat

A study was designed to evaluate ameliorative effect of propolis against methoxychlor (MXC) induced ovarian toxicity in rat. The organochlorine pesticide (MXC) is a known endocrine disruptor with estrogenic, anti-estrogenic, and anti-androgenic properties. To investigate whether chronic exposure to MXC could cause ovarian dysfunction, two groups of Sprague–Dawley adult female rats were exposed to MXC alone in a dose of 200mg/kg, twice/weekly, orally or MXC dose as previous plus propolis in a dose of 200mg/l/day, in drinking water for 10 months. Another two groups of rat were given corn oil (control) or propolis. Multiple reproductive parameters, ovarian weight, serum hormone levels, ovarian oxidative status and ovarian morphology were examined. In MXC-exposed group, there is a significant decrease in body and ovarian weight vs. control. MXC decreases serum estradiol and progesterone levels. A significant increase in the levels of lipid peroxidation was obtained while a significant decrease of the total antioxidant was recorded. Ovarian histopathology showed primary, secondary and vesicular follicles displaying an atretic morphology. Increase in the ovarian surface epithelium height accompanied with vacuolated, pyknotic oocytes were obtained. The previous toxic effects were neutralized by the administration of propolis in MXC+propolis group. The present results suggest that propolis may be effective in decreasing of MXC-induced ovarian toxicity in rat.

Perinatal exposure to methoxychlor enhances adult cognitive responses and hippocampal neurogenesis in mice.

During perinatal life, sex steroids, such as estradiol, have marked effects on the development and function of the nervous system. Environmental estrogens or xenoestrogens are man-made chemicals, which animal and human population encounter in the environment and which are able to disrupt the functioning of the endocrine system. Scientific interest in the effects of exposure to xenoestrogens has focused more on fertility and reproductive behaviors, while the effects on cognitive behaviors have received less attention. Therefore, the present study explored whether the organochlorine insecticide Methoxychlor (MXC), with known xenoestrogens properties, administered during the perinatal period (from gestational day 11 to postnatal day 8) to pregnant-lactating females, at an environmentally relevant dose (20 µg/kg (body weight)/day), would also affect learning and memory functions depending on the hippocampus of male and female offspring mice in adulthood. When tested in adulthood, MXC perinatal exposure led to an increase in anxiety-like behavior and in short-term spatial working memory in both sexes. Emotional learning was also assessed using a contextual fear paradigm and MXC treated male and female mice showed an enhanced freezing behavior compared to controls. These results were correlated with an increased survival of adult generated cells in the adult hippocampus. In conclusion, our results show that perinatal exposure to an environmentally relevant dose of MXC has an organizational effect on hippocampus-dependent memory and emotional behaviors.

Immunotoxicity of the organochlorine pesticide methoxychlor in female ICR, BALB/c, and C3H/He mice

Several types of pesticides, including organochlorines, are known to suppress or modulate immune responses. The present study evaluated the immunotoxicity of the organochlorine pesticide methoxychlor (MXC) in female BALB/c, C3H/He, and ICR mice. Mice were given oral MXC doses of 0, 30, 100, and 300 mg/kg each day for 7 consecutive days. On day 4, the mice also received an intravenous injection of sheep red blood cells (SRBC). The splenic plaque-forming cell (PFC) IgM response and the serum anti-SRBC IgM antibody titer were evaluated while splenic lymphocytes were counted by flow cytometry and the spleen underwent histopathological analysis. Significant decreases in IgM PFC responses were seen in BALB/c, C3H/He, and ICR mice that received MXC doses of 100 and 300 mg/kg. Similar changes in serum anti-SRBC IgM antibody titers occurred in three strain mice. Flow cytometric analysis revealed significantly decreased splenic T-cell (CD3+) populations in a dose dependent manner in BALB/c mice, and in the 300 mg/kg of MXC-treated group of C3H/He mice. Germinal center (GC) B-cell (CD19+PNA+) populations were significantly decreased in the 300 mg/kg of MXC-treated groups of all three mouse strains and in the 30 and 100 mg/kg of MXC-treated groups of BALB/c and C3H/He strain mice. Histopathological analysis revealed decreased cellularity of the periarteriolar lymphoid sheath (PALS; T-cell area) and decreased GC development in all three strains of mice treated with 300 mg/kg MXC. These results suggest that MXC has an immune-suppressive effect in mice, and that our protocol may be useful for rapidly detecting immunosuppression induced by environmental chemicals.

Methoxychlor‐Induced Ovarian Follicle Toxicity in Mice: Dose and Exposure Duration‐Dependent Effects

Methoxychlor (MXC) is specifically known to target ovarian antral follicles, increasing atresia (death via apoptosis) in them. This is of concern because females are born with a finite pool of ovarian follicles. Only limited studies have explored the phenomenon of a reduced fertility threshold for effect based on the percentage of antral follicle atresia. In this article, we report on adult female CD-1 mice exposed intraperitoneally to various doses of MXC for 5, 10, 20, and 30 days. In the 20-day treatment, mice were dosed with either the vehicle or MXC at 64 or 96 mg/kg/day, whereas in the 30-day treatment, mice were dosed with vehicle or MXC at 48, 64, or 96 mg/kg/day. The mice that were dosed with MXC for 30 days were also mated with untreated males for a determination of overall fertility. A significantly increased percentage (50%) of atretic antral follicles was observed only after 20 and 30 days of treatment. Specifically, mice treated with MXC64 for 20 and 30 days had an increased percentage of atretic antral follicles compared with vehicle-treated mice. Interestingly, mice dosed with MXC96 had an increased percentage of atretic antral follicles after 30 days, but not after 20 days of treatment compared with vehicle-treated mice. Overall fertility of the mice was not different compared with controls. The results indicate that as much as a 50% increase in atretic antral follicles does not affect the immediate fertility of the mice.

Methoxychlor inhibits growth and induces atresia through the aryl hydrocarbon receptor pathway in mouse ovarian antral follicles

Methoxychlor (MXC) is an organochlorine pesticide used against pests that attack crops, vegetables, and livestock. MXC inhibits growth and induces atresia (death) of mouse ovarian antral follicles in vitro. Since several studies indicate that many chemicals act through the aryl hydrocarbon receptor (AHR) pathway, the current study tested the hypothesis that MXC binds to the AHR to inhibit growth and induce atresia of antral follicles. The data indicate that MXC binds to AHR. Further, a relatively high dose of MXC (100μg/ml) inhibits growth and induces atresia in both wild-type (WT) and AHR null (AHRKO) follicles, whereas a lower dose of MXC (10μg/ml) inhibits growth and induces atresia in WT, but not in AHRKO follicles. These data indicate that AHR deletion partially protects antral follicles from MXC induced slow growth and atresia. Collectively, these data show that MXC may act through the AHR pathway to inhibit follicle growth and induce atresia in antral follicles of the ovary.

Neonatal injections of methoxychlor decrease adult rat female reproductive behavior

Methoxychlor (MXC), a commonly used pesticide, has been labeled as an endocrine disruptor. To evaluate the impact of neonatal exposure to MXC on female reproduction, female Sprague-Dawley rats were given subcutaneous injections on postnatal days 1, 3, and 5. The injections contained 1.0mg MXC, 2.0mg MXC, 10μg 17β-estradiol benzoate (positive control), or sesame oil (vehicle). The injections of MXC had no effect on anogenital distance or day of vaginal opening. Treatment with either 2.0mg MXC or estradiol significantly increased the total number of days with vaginal keratinization. Treatment with MXC had no effect on ability to exhibit a mating response as an adult female, although the high dose MXC (2.0) and the positive control (estradiol) animals demonstrated a decrease in degree of receptivity, a decrease in proceptive behavior and an increase in rejection behavior. These data suggest that higher doses of MXC given directly to pups during the neonatal period can act as an estrogen and alter aspects of the nervous system, impacting adult reproductive characteristics.

Methoxychlor induces apoptosis via mitochondria- and FasL-mediated pathways in adult rat testis

In the past few years, there has been much concern about the adverse health effects of environmental contaminants in general and organochlorine in particular. Studies have shown the repro-toxic effects of long-term exposure to methoxychlor, a member of the organochlorine family. However, the insight into the mechanisms of gonadal toxicity induced by methoxychlor is not well known. In the present study we sought to elucidate the mechanism(s) underpinning the gonadal effects within hours of exposure to methoxychlor. Experimental rats were divided into six groups of four each. Animals were orally administered with a single dose of methoxychlor (50 mg/kg body weight) and killed at 0, 3, 6, 12, 24, and 72 h post-treatment. The levels and time-course of induction of apoptosis-related proteins like cytochorome C, caspase 3 and procaspase 9, Fas–FasL and NF-κB were determined to assess sequential induction of apoptosis in the rat testis. DNA damage was assessed by TUNEL assay and flowcytometry. Administration of methoxychlor resulted in a significant increase in the levels of cytosolic cytochrome c and procaspase 9 as early as 6 h following exposure. Time-dependent elevations in the levels of Fas, FasL, pro- and cleaved caspase 3 were observed. The DNA damage was measured and showed time-dependent increase in the TUNEL positive cells, and also by flowcytometry of testicular cells. The study demonstrates induction of testicular apoptosis in adult rats following exposure to a single dose of methoxychlor.

Methoxychlor‐induced alteration in the levels of HSP70 and clusterin is accompanied with oxidative stress in adult rat testis

Methoxychlor, an organochlorine pesticide, has been reported to induce abnormalities in male reproductive tract. However, the insight into the mechanisms of gonadal toxicity induced by methoxychlor is not well known. We investigated whether treatment with methoxychlor would alter the levels of stress proteins, heat shock proteins (HSP), and clusterin (CLU), and oxidative stress-related parameters in the testis of adult male rats. Animals were exposed to a single dose of methoxychlor (50 mg/kg body weight) orally and were terminated at various time points (0, 3, 6, 12, 24, and 72 h) using anesthetic ether. The levels of HSP70, CLU, and the activities of superoxide dismutase (SOD), catalase, and lipid peroxidation levels were evaluated in a 10% testis homogenate. A sequential reduction in the activities of catalase and SOD with concomitant increase in the levels of thiobarbituric acid reactive substance (TBARS) was observed. These changes elicited by methoxychlor were very significant between 6-12 h of posttreatment. Immunoblot analysis of HSP revealed the expression of HSP72, an inducible form of HSP, at certain time points (3-24 h) following exposure to methoxychlor. Similarly, the levels of secretory CLU (sCLU) were also found to be elevated between 3-24 h of treatment. The present data demonstrate methoxychlor-elicited increase in the levels of inducible HSP72 and sCLU, which could be a part of protective mechanism mounted to reduce cellular oxidative damage.

Transient inhibitory effect of methoxychlor on testicular steroidogenesis in rat: an in vivo study

Methoxychlor, an organochlorine pesticide, has been reported to induce reproductive abnormalities in male reproductive tract. To get more insight into the mechanism(s) of gonadal toxicity provoked by methoxychlor, we investigated whether treatment with methoxychlor at low observed adverse effect level (LOAEL) would alter the activities of steroidogenic enzymes such as Delta(5)3beta-hydroxysteroid dehydrogenase (3beta-HSD) and Delta(5)17beta-hydroxysteroid dehydrogenase (17beta-HSD), the expression levels of steroidogenic acute regulatory (StAR) protein and androgen binding protein (ABP) in the testis of adult male rats. The experimental rats were exposed to a single dose of methoxychlor (50 mg/kg body weight) orally. The rats were killed at 0, 3, 6, 12, 24 and 72 h following treatment using anesthetic ether and testes were collected, processed and used to measure the activities of 3beta-HSD, 17beta-HSD, levels of hydrogen peroxide produced and the expression levels of StAR protein, and ABP. Methoxychlor administration resulted in a sequential reduction in the expression of StAR protein and activities of 3beta-HSD, 17beta-HSD with concomitant increase in the levels of hydrogen peroxide in the testis. These changes were significant between 6-12 h following treatment. The levels of ABP declined at 6-12 h following exposure to methoxychlor. The present study demonstrates transient effect of methoxychlor at LOAEL on testicular steroidogenesis and the possible role of hydrogen peroxide in mediating these effects.

Methoxychlor Induces Atresia of Antral Follicles in ERα-Overexpressing Mice

Methoxychlor (MXC) is a pesticide that is known to bind to estrogen receptor alpha (ERalpha) and to induce atresia of antral ovarian follicles. Although studies have shown that MXC is toxic to the ovary, we hypothesize that perturbation to the estrogen-signaling system (i.e., increase or decrease in estrogen sensitivity) might alter ovarian responsiveness to MXC. Thus, we examined whether ERalpha overexpression alters the ability of MXC to increase follicle atresia. To do so, we employed a transgenic mouse model in which ERalpha can be inducibly overexpressed in animal tissues (ERalpha overexpressors). We dosed female controls and ERalpha overexpressors with sesame oil (vehicle control) or MXC (32 and 64 mg/kg/day) for 20 days. After dosing, the ovaries were collected for histological evaluation of follicle numbers and follicle atresia, while blood was collected for measurements of hormones. Estrous cycles were determined in all animals to ensure that all were terminated during estrus. Although there were no significant effects of MXC on the numbers of primordial, primary, and preantral follicles in both controls and ERalpha overexpressors, there was an effect on antral follicles. Specifically, our data indicate that 32 and 64 mg/kg MXC increased the percentage of atretic follicles compared to vehicle in both control and ERalpha overexpressor groups. Moreover, there was a clear trend toward greater sensitivity to 64 mg/kg MXC in ERalpha-overexpressing mice compared to control animals. Specifically, at the 64-mg/kg MXC dose, ERalpha-overexpressing mice had a significantly higher percentage of atretic follicles compared to control animals (controls = 21.5 +/- 3%, n = 5; ERalpha overexpressors = 37 +/- 23%, n = 9, p < or = 0.05 vs. controls). After 20 days of dosing, there were no differences in estradiol levels between controls and ERalpha-overexpressing mice in all treatment groups. Follicle-stimulating hormone (FSH) levels were similar in sesame oil-treated control mice and control mice treated with 32 mg/kg MXC, while control mice treated with 64 mg/kg MXC had significantly lower levels of FSH compared to sesame oil-treated controls (sesame oil = 4.31 +/- 0.7, MXC [64 mg/kg/day] = 1.89 +/- 0.4, n = 3, p < or = 0.02 vs. sesame oil). ERalpha-overexpressing mice treated with sesame oil, 32 or 64 mg/kg MXC, had similar FSH levels. Thus, we observed an increased percentage of atretic antral follicles in ERalpha-overexpressing mice treated with MXC compared to control mice treated with the same compound, suggesting that the ERalpha-signaling pathway plays an important role in MXC-induced atresia. The trend toward greater sensitivity to MXC in ERalpha-overexpressing mice compared to control animals cannot be explained by alterations in estradiol and/or FSH levels.

Consequences of endocrine disrupting chemicals on reproductive endocrine function in birds: Establishing reliable end points of exposure

It has been difficult to establish reliable indices of exposure to endocrine disrupting chemicals (EDCs) appropriate for a variety of avian species because of a vast array of reproductive strategies. Data from mammals, reptiles and fish provide insight on likely mechanisms of action for EDCs. However, many of the effects of EDCs are weaker than the actions of the native hormones, making it difficult to assess adverse effects in domestic and wild birds. It is clear that differential sensitivity to EDCs exists across species, due to the timing and mode of exposure, compound toxicity and age of the individual. Our studies on EDCs are conducted in the quail model system, with focus on reproductive endocrine, neuroendocrine and behavioral responses. Studies have included EDC exposure, either by egg injection or via diet. Results from egg injection studies showed the following: (1) estradiol administered by embryonic day 12 demasculinized male sexual behavior, altered hypothalamic neurotransmitters and reduced hen day production and fertility in a dose dependent fashion, (2) methoxychlor (MXC) or vinclozolin impaired male sexual behavior in adult quail and (3) DDE exposure impaired reproductive and immune related end points. Two-generation studies were conducted on Japanese and northern bobwhite quail with dietary methoxychlor (MXC) exposure (0, 5 and 10 ppm) beginning in adults (P1), continuing in their offspring (F1), with F2 offspring raised on control diet. MXC exposure impaired male sexual behavior, hypothalamic catecholamines and plasma steroid hormones. Moreover, MXC exposure had reproductive consequences observable at both the lower and higher doses of MXC in F1 and F2 generations. These data demonstrate that embryonic EDC exposure interferes with sexual differentiation of neural systems that direct reproduction.

Pesticides and SLE: Is the Link Estrogenic?

Autoimmune diseases are multifactorial in nature and likely involve both environmental and genetic components. Estrogen is one environmental component that has been studied in relation to systemic lupus erythematosus (SLE) based on a number of clues. Like many other autoimmune diseases, SLE—a chronic disorder of uncertain cause and a varied clinical course—is more common among women, and onset is especially likely during childbearing years. In the (NZB × NZW)F1 mouse model of SLE, females develop more severe disease and die earlier than males; treating females with androgens (male hormones) slows the disease, while castrating males accelerates it. Several organochlorine pesticides can emulate estrogen in the body. Now a group of Florida researchers has assessed the possible role of these compounds in causing SLE [EHP 113:323–328]. The researchers used female (NZB × NZW)F1 mice to study to effects of three estrogenic pesticides. They removed the ovaries of some of the animals to eliminate endogenous estrogen, while others were left intact. They then dosed the ovariectomized animals with the synthetic estrogen 17β-estradiol or with one of two doses of DDT, methoxychlor, or chlordecone. SLE can result in kidney failure due to glomerulonephritis, a deterioration of the glomerules that “filter” the blood, retaining nutrients and discarding wastes. So the team chose glomerulonephritis as an end point, and determined onset of the condition by measuring protein and blood urea nitrogen in the urine. All three pesticides accelerated the onset of SLE. DDT and methoxychlor appeared to have roughly the same influence on SLE development as endogenous estrogen. The lower dose of methoxychlor tested—equaling approximately 1.2 milligrams per kilogram per day—produced kidney damage, even though it was fourfold lower than the no-observable-effect level used by the U.S. Environmental Protection Agency to calculate an oral reference dose for methoxychlor. This, the authors wrote, suggests that autoimmunity might be among the most sensitive measures of harm caused by methoxychlor. Chlordecone produced the strongest response, so the team experimented further with lower doses of this compound. Chlordecone was commonly used in agriculture and some household products to kill ants and roaches in the 1960s and early 1970s. It was banned in the United States in the late 1970s, but it degrades slowly and still persists at some contaminated sites. Examination of the kidney revealed a deterioration characteristic of the usual course of SLE, including the appearance of immune complexes of antibodies and target cells, even at the lowest chlordecone dose—a dose that would usually be considered a no-observable-effect level. Chlordecone also raised levels of antibodies to native, double-stranded DNA, another specific marker for SLE. Despite evidence that all three pesticides accelerated the course of SLE, the chemicals did not increase uterine weight, which is a normal result of estrogen treatment. The authors speculate, therefore, that uterine hypertrophy might be a poor measure of the estrogenic effects of these pesticides, or that estrogenicity is not the mechanism that links pesticide exposure to SLE and renal failure. Interestingly, the organochlorines caused about the same level of disease as the synthetic estrogen used as a positive control. However, because the mice studied almost always develop SLE, the research did not demonstrate that the organochlorines would cause SLE in animals that would not otherwise get the disease.

Embryonic co-exposure to methoxychlor and Clophen A50 alters sexual behavior in adult male quail

Embryonic exposure to estrogens and estrogenic pollutants is known to demasculinize sexual behavior in adult male Japanese quail. In the present study, we administered the insecticide methoxychlor to quail eggs at a dose of 150 microg/g egg and then studied sexual behavior and other reproductive variables in adult males. In a second experiment we administered the same dose of methoxychlor together with 10 microg/g egg of the commercial polychlorinated biphenyl (PCB) mixture Clophen A50 (CA50) and also CA50 alone. Neither methoxychlor nor CA50 had any significant effects by themselves, but when they were administered together a significant reduction in male sexual behavior was observed. It seems likely that induction of biotransformation enzymes in the embryos by CA50 resulted in increased conversion of methoxychlor to the more estrogenic metabolite 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (HPTE).

Methoxychlor-induced atresia in the mouse involves Bcl-2 family members, but not gonadotropins or estradiol.

Methoxychlor (MXC) is an organochlorine pesticide that increases the rate of ovarian atresia. To date, little is known about the mechanism by which MXC induces atresia. Because Bcl-2 (an antiapoptotic factor), Bax (a proapoptotic factor), gonadotropins, and estradiol are important regulators of atresia in the ovary, the purpose of this study was first to examine whether MXC-induced atresia occurred through alterations in Bcl-2 or Bax, and second, to examine the effect of MXC on gonadotropins, estradiol, and their receptors. CD-1 mice were dosed with 8-64 mg kg(-1) day(-1) MXC or vehicle (sesame oil). Ovaries were subjected to analysis of antral follicle numbers, Bcl-2, Bax, estrogen receptor, and follicle-stimulating hormone receptor levels. Blood was used to measure gonadotropins and estradiol. In some experiments, mice that overexpressed Bcl-2 or mice that were deficient in Bax were dosed with MXC or vehicle and their ovaries were analyzed for atresia. MXC caused a dose-dependent increase in the percentage of atretic antral follicles compared with controls at the 32 and 64 mg kg(-1) day(-1) doses of MXC. MXC treatment did not result in changes in Bcl-2 levels, but it did result in an increase in Bax levels in antral follicles. MXC treatment did not affect gonadotropin or estradiol levels, nor did it affect the levels of follicle-stimulating hormone or estrogen receptors. Mice that overexpressed Bcl-2 or mice that were deficient in Bax were protected from MXC-induced atresia. These data suggest that MXC induces atresia through direct effects on the Bax and Bcl-2 signaling pathways in the ovary.

Effects of methoxychlor exposure during perinatal period on reproductive function after maturation in rats.

Methoxychlor (MXC) is a non-steroidal pesticide that is known to possess estrogenic activity, and therefore may be potentially hazardous to the development and/or reproduction. The present study assessed the effects of perinatal exposure to MXC on reproductive function after maturation in both male and female rats. Pregnant rats were fed a phytoestrogen-free diet containing different doses of MXC (24, 240, and 1200 ppm) from day 15 of gestation to day 10 after parturition, and reproductive functions of offspring were examined after maturation. In males, MXC exposure during the perinatal period decreased serum LH and FSH, but not testosterone levels, but it did not affect copulatory behavior. In females, MXC exposure prolonged the days exhibiting cornified vaginal smears during the estrous cycle. In addition, both the lordosis reflex and preovulatory LH surge on the presumptive proestrous evening were suppressed in MXC-exposed females. These results suggest that perinatal exposure to MXC exerts permanent effects on several aspects of the reproductive function in both male and female rats.

Preimplantation mouse embryo development as a target of the pesticide methoxychlor

Effects of methoxychlor (MXC) and estradiol-17β (E) were studied in mouse preimplantation embryos. Pregnant mice received s.c. injections of sesame oil only, 10 μg E, or 0.5 mg purified (95%) MXC on Days 2–4 of pregnancy (plug=Day 1). Another group received a single dose of 2.5 μg E on Day 2 only. Based on the average weight of pregnant females, 10 μg of estradiol was equivalent to 0.33 mg/kg of bw, 2.5 μg of estradiol was equivalent to 0.082 mg/kg of bw, and the 0.5-mg dose of MXC was equivalent to 16.5 mg/kg of bw. All embryos were collected for analyses on Day 4. MXC and both estradiol-17β doses suppressed embryonic development to blastocyst, decreased embryo cell numbers, and caused abnormal blastocyst formation. The high estradiol-17β dose significantly increased the percent degenerating embryos and caused a tube-locking effect, with retention of embryos in the oviduct. In contrast to estradiol-17β, MXC at the dose used in this study did not alter tubal transport of embryos. Also in contrast to estradiol-17β, MXC increased the percentage of nuclear fragmentation and micronuclei. In preimplantation embryos, MXC and estradiol-17β both suppressed embryo development. MXC effects were, however, different from those of estradiol-17β, indicating a difference in mechanism of action, possibly due to cytotoxicity and induction of apoptosis.