Effects of concurrent exposure to tributyltin and 1,1-dichloro-2,2 bis (p-chlorophenyl) ethylene (p,p'-DDE) on immature male Wistar rats

Adaptation of Brown Adipose Tissue in Response to Chronic Exposure to the Environmental Pollutant 1,1-Dichloro-2,2-bis(p-chlorophenyl) Ethylene (DDE) and/or a High-Fat Diet in Male Wistar Rats

Brown adipose tissue (BAT) participates in thermogenesis and energy homeostasis. Studies on factors capable of influencing BAT function, such as a high-fat diet (HFD) or exposure to environmental pollutants, could be useful for finding metabolic targets for maintaining energy homeostasis. We evaluated the effect of chronic exposure to dichlorodiphenyldichloroethylene (DDE), the major metabolite of dichlorodiphenyltrichloroethane (DDT), and/or a HFD on BAT morphology, mitochondrial mass, dynamics, and oxidative stress in rats. To this end, male Wistar rats were treated for 4 weeks with a standard diet, or a HFD alone, or together with DDE. An increase in paucilocular adipocytes and the lipid droplet size were observed in HFD-treated rats, which was associated with a reduction in mitochondrial mass and in mitochondrial fragmentation, as well as with increased oxidative stress and upregulation of the superoxide dismutase-2. DDE administration mimics most of the effects induced by a HFD on BAT, and it aggravates the increase in the lipid droplet size when administered together with a HFD. Considering the known role of oxidative stress in altering BAT functionality, it could underlie the ability of both DDE and a HFD to induce similar metabolic adaptations in BAT, leading to reduced tissue thermogenesis, which can result in a predisposition to the onset of energy homeostasis disorders.

Exposure to Dichlorodiphenyldichloroethylene (DDE) and Metallothionein Levels in Rats Fed with Normocaloric or High-Fat Diet: A Review

The growing number of studies on metallothioneins (MTs), cysteine-rich metal-binding proteins, have been disclosing new functions of these proteins. Thanks to their inducibility, they were considered to play a pivotal role in regulating trace metals homeostasis and in detoxification from heavy metals; nowadays, it is known that they are involved in various physiological and pathological processes, such as regulation of apoptosis, elimination of free radicals, and protection of nucleic acids against toxic insults. MT induction has been demonstrated following stress factors other than heavy metals, such as endocrine-disrupting chemicals, insecticides, and herbicides. However, retrieved data are often controversial: in some cases, xenobiotics elicit MT expression and synthesis; under different conditions, they lead to a decrease in cellular MT content. This review describes the MT response to dichlorodiphenyltrichloroethane (DDT) contamination in mammalian tissues. In particular, attention focuses on changes in MT expression, synthesis, and localization in rat liver, kidneys, and testes following oral administration of dichlorodiphenyldichloroethylene (DDE), the main metabolite of DDT, under normal dietary conditions or in combination with a high fat diet potentially able to increase the cellular uptake of this lipophilic pesticide. The potential connection between MT expression and synthesis, lipophilic substances and trace metals availability is also discussed.

Oxidative stress and mitochondrial uncoupling protein 2 expression in hepatic steatosis induced by exposure to xenobiotic DDE and high fat diet in male Wistar rats

Oxidative stress plays a key role in steatohepatitis induced by both xenobiotic agents and high fat diet (HFD). The present study aimed to evaluate hepatic oxidative stress and anti-oxidant systems response in rats exposed to HFD and/or non-toxic dose of dichlorodiphenyldichloroethylene (DDE), the first metabolite of dichlorodiphenyltrichloroethane. Groups of 8 rats were so treated for 4 weeks: 1- standard diet (N group); 2- standard diet plus DDE (10 mg/kg b.w.) (N+DDE group); 3- HFD (D group); 4- HFD plus DDE (D+DDE group). Oxidative stress was analyzed by determining malondialdehyde as lipid peroxidation product, while the anti-oxidant systems were evaluating by measuring the levels of the principal cytosolic and mitochondrial antioxidant proteins and enzymes, namely superoxide dismutase 1 and 2 (SOD1, SOD2), glutathione peroxidase 1 (GPx1) and uncoupling protein 2 (UCP2) involved in the control of hepatic reactive oxygens species (ROS) accumulation. The results showed malondialdehyde accumulation in livers of all groups, confirming the pro-oxidant effects of both HFD and DDE, but with a greater effect of DDE in absence of HFD. In addition, we found different levels of the analyzed anti-oxidant systems in the different groups. DDE mainly induced UCP2 and SOD2, while HFD mainly induced GPx1. Noteworthy, in the condition of simultaneous exposure to DDE and HFD, the anti-oxidant response was more similar to the one induced by HFD than to the response induced by DDE. Present findings confirmed that both HFD and xenobiotic exposure induced hepatic oxidative stress and showed that the anti-oxidant defense response was not the same in the diverse groups, suggesting that UCP2 induction could be an adaptive response to limit excessive ROS damage, mainly in condition of xenobiotic exposure.

Combined effects of DDE and hyperlipidic diet on metallothionein expression and synthesis in rat tissues

Metallothionein is well known for its detoxificant and anti-oxidant properties and has been shown to be effective to prevent hydroxyl radical-generated DNA degradation. The purpose of this investigation was to analyze the combined effect of two factors promoting cellular oxidative-stress, that is, the administration of the pesticide dichloro-diphenyl-dichloroethylene (DDE) and a high fat diet, on metallothionein expression and synthesis in rat liver and kidney. DDE is the main metabolite of dichloro-diphenyl-trichloroethane (DDT), and is commonly found in the food chain and in all tissues of living organisms, carried by the fats. Male Wistar rats were fed with a standard (N) or a high fat (HF) diet and exposed to DDE (10 mg/kg body mass, N + DDE and HF + DDE groups) or vehicle (corn oil, N, and HF groups) via gavage every day for 28 days. Tissues histology was determined by light microscopy analysis; differences in metallothionein gene expression and synthesis by real-time PCR and western blot, respectively. Finally, protein cellular localization was established by immunocytochemistry. The results showed a different involvement of metallothionein in defending tissues from HF- and DDE-induced oxidative stress, suggesting that hepatic and renal cells use different strategies against pro-oxidant species. In both cell types a marked increase in the metallothionein content was observed in the nucleus, with a concomitant drop of the cytoplasmatic protein, either under HF- and DDE-stress conditions; however, no synergistic or additive effects were observed between the action of fats and pesticide. These findings reinforce the role of metallothionein in protecting DNA from oxidative damage.

Overview of the Pathophysiological Implications of Organotins on the Endocrine System

Organotins (OTs) are pollutants that are used widely by industry as disinfectants, pesticides, and most frequently as biocides in antifouling paints. This mini-review presents the main evidences from the literature about morphophysiological changes induced by OTs in the mammal endocrine system, focusing on the metabolism and reproductive control. Similar to other toxic compounds, the main effects with potential health risks to humans and experimental animals are not only related to dose and time of exposure but also to age, gender, and tissue/cell exposed. Regarding the underlying mechanisms, current literature indicates that OTs can directly damage endocrine glands, as well as interfere with neurohormonal control of endocrine function (i.e., in the hypothalamic-pituitary axis), altering hormone synthesis and/or bioavailability or activity of hormone receptors in the target cells. Importantly, OTs induces biochemical and morphological changes in gonads, abnormal steroidogenesis, both associated with reproductive dysfunctions such as irregular estrous cyclicity in female or spermatogenic disorders in male animals. Additionally, due to their role on endocrine systems predisposing to obesity, OTs are also included in the metabolism disrupting chemical hypothesis, either by central (e.g., accurate nucleus and lateral hypothalamus) or peripheral (e.g., adipose tissue) mechanisms. Thus, OTs should be indeed considered a major endocrine disruptor, being indispensable to understand the main toxic effects on the different tissues and its causative role for endocrine, metabolic, and reproductive dysfunctions observed.

Effects of tributyltin chloride on developing mouse oocytes and preimplantation embryos

Tributyltin, an organotin, is ubiquitous in estuaries and freshwater systems. Previous reports suggest that tributyltin is an endocrine disruptor in many wildlife species and it inhibits aromatase in mammalian placental and granulosa-like tumor cell lines. However, no evidence showing the effects of tributyltin on oocytes or preimplantation embryonic developmental competence exists. Therefore, we investigated the role of tributyltin chloride (TBTCl) in the development of female oocytes and preimplantation embryos. Briefly, female ICR mice were gavaged with 0 (vehicle), 4, and 8 mg/kg of TBTCl each day for 18 days. The fluorescence intensity analysis showed that the 5-methylcytosine level decreased after TBTCl treatment, indicating that the general DNA methylation level decreased in the treated oocytes. Our results demonstrate that TBTCl treatment results in decreased mRNA levels of imprinted genes H19, Igf2r, and Peg3 during oocyte growth. The TBTCl-treated oocytes showed a significant increase in reactive oxygen species levels in germinal vesicle oocytes. In TBTCl-treated oocytes, there was no difference in GPx and Sod1 expression, but a decreased mRNA level of Cat occurred when compared with control. Moreover, the blastocysts with TBTCl exposure displayed higher apoptotic signals. These results suggest that TBTCl induces developmental defects in oocytes and preimplantation embryos.

Chlorinated persistent organic pollutants, obesity, and type 2 diabetes

Persistent organic pollutants (POPs) are lipophilic compounds that travel with lipids and accumulate mainly in adipose tissue. Recent human evidence links low-dose POPs to an increased risk of type 2 diabetes (T2D). Because humans are contaminated by POP mixtures and POPs possibly have nonmonotonic dose-response relations with T2D, critical methodological issues arise in evaluating human findings. This review summarizes epidemiological results on chlorinated POPs and T2D, and relevant experimental evidence. It also discusses how features of POPs can affect inferences in humans. The evidence as a whole suggests that, rather than a few individual POPs, background exposure to POP mixtures-including organochlorine pesticides and polychlorinated biphenyls-can increase T2D risk in humans. Inconsistent statistical significance for individual POPs may arise due to distributional differences in POP mixtures among populations. Differences in the observed shape of the dose-response curves among human studies may reflect an inverted U-shaped association secondary to mitochondrial dysfunction or endocrine disruption. Finally, we examine the relationship between POPs and obesity. There is evidence in animal studies that low-dose POP mixtures are obesogenic. However, relationships between POPs and obesity in humans have been inconsistent. Adipose tissue plays a dual role of promoting T2D and providing a relatively safe place to store POPs. Large prospective studies with serial measurements of a broad range of POPs, adiposity, and clinically relevant biomarkers are needed to disentangle the interrelationships among POPs, obesity, and the development of T2D. Also needed are laboratory experiments that more closely mimic real-world POP doses, mixtures, and exposure duration in humans.

Adipocytes under assault: environmental disruption of adipose physiology

The burgeoning obesity epidemic has placed enormous strains on individual and societal health mandating a careful search for pathogenic factors, including the contributions made by endocrine disrupting chemicals (EDCs). In addition to evidence that some exogenous chemicals have the capacity to modulate classical hormonal signaling axes, there is mounting evidence that several EDCs can also disrupt metabolic pathways and alter energy homeostasis. Adipose tissue appears to be a particularly important target of these metabolic disruptions. A diverse array of compounds has been shown to alter adipocyte differentiation, and several EDCs have been shown to modulate adipocyte physiology, including adipocytic insulin action and adipokine secretion. This rapidly emerging evidence demonstrating that environmental contaminants alter adipocyte function emphasizes the potential role that disruption of adipose physiology by EDCs may play in the global epidemic of metabolic disease. Further work is required to better characterize the molecular targets responsible for mediating the effects of EDCs on adipose tissue. Improved understanding of the precise signaling pathways altered by exposure to environmental contaminants will enhance our understanding of which chemicals pose a threat to metabolic health and how those compounds synergize with lifestyle factors to promote obesity and its associated complications. This knowledge may also improve our capacity to predict which synthetic compounds may alter energy homeostasis before they are released into the environment while also providing critical evidentiary support for efforts to restrict the production and use of chemicals that pose the greatest threat to human metabolic health. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.

p,p'-DDE induces apoptosis and mRNA expression of apoptosis-associated genes in testes of pubertal rats

One,1-dichloro-2,2 bis(p-chlorophenyl) ethylene (p,p'-DDE), the major metabolite of 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (DDT), is a known persistent organic pollutant and male reproductive toxicant. It has antiandrogenic effect. However, the mechanism by which p,p'-DDE exposure causes male reproductive toxicity remains unknown. To elucidate the mechanism underpinning the testicular effects of p,p'-DDE, we sought to investigate apoptotic effects and mRNA expression of apoptosis-associated genes in the testis of pubertal rats, including Fas, FasL, calpain-1, cytochrome c, Bax, Bcl-w, Bak, and caspase-3, -8, -9, -12. Animals were administered with different doses of p,p'-DDE (0, 20, 60, 100 mg/kg body weight) every other day by intraperitoneal injection for 10 days. The results indicated that p,p'-DDE exposure at over 20 mg/kg body weight showed the induction of apoptotic cell death. p,p'-DDE could induce decrease in SOD and GSH-Px activity of serum in 60 mg/kg body weight group. Significant elevations in the mRNA levels of Fas, FasL, calpain-1, cytochrome c, Bax, Bak, and caspase-3, -8, -9, -12 were observed in testis of rat treated with p,p'-DDE. Taken together, these results lead us to speculate that in vivo exposure to p,p'-DDE might induce testicular apoptosis in pubertal rats through the involvement of Fas/FasL, mitochondria and endoplasmic reticulum-mediated pathways.

Tributyltin causes obesity and hepatic steatosis in male mice

Organotin compounds such as tributyltin (TBT) have been used worldwide in agriculture and industry as biocides, heat stabilizers, and chemical catalysts. However, few studies addressing the effects of TBT on growth and metabolism have been reported. This study was conducted to investigate the effects of TBT at low doses (0.5, 5, and 50 μg/kg) on body weight gain in male mice exposed as from puberty and to determine the alterations in related hormones. The results showed that exposure to TBT for 45 days resulted in an increase in body weight gain and hepatic steatosis accompanied with hyperinsulinemia and hyperleptinemia. Reduction of hepatic adiponectin levels in a dose-dependent manner was related to the lipid increase in the liver. These results suggest that chronic and repeat exposure to low doses of TBT can result in obesity and hepatic steatosis and induce the occurrence of insulin and leptin resistance.

Childhood obesity and environmental chemicals

Childhood and adolescent rates of obesity and overweight are continuing to increase in much of the world. Risk factors such as diet composition, excess caloric intake, decreased exercise, genetics, and the built environment are active areas of etiologic research. The obesogen hypothesis, which postulates that prenatal and perinatal chemical exposure can contribute to risk of childhood and adolescent obesity, remains relatively underexamined. This review surveys numerous classes of chemicals for which this hypothesis has been explored. We focus on human data where they exist and also discuss the findings of rodent and cell culture studies. Organochlorine chemicals as well as several classes of chemicals that are peroxisome proliferator-activated receptor agonists are identified as possible risk factors for obesity. Recommendations for future epidemiologic and experimental research on the chemical origins of obesity are also given.

Sex-dependent aromatase activity in rat offspring after pre- and postnatal exposure to triphenyltin chloride

Triphenyltin (TPT) is an organotin compound (OTC) previously widely used as an antifouling agent in paints applied in the marine environment, a fungicide, and as an agricultural pesticide. In female aquatic invertebrates, certain OTCs induce the so-called imposex, an abnormal induction of male sex characteristics. OTC-induced environmental endocrine disruption also occurs in fish and mammals and a number of in vivo and in vitro studies have argued that OTCs may act through inhibition of the aromatase enzyme. In vivo studies supporting the aromatase inhibition hypothesis in mammals are lacking. Recently, the causal relationship between inhibition of aromatase and imposex was questioned, suggesting aromatase independent mechanisms of action for this phenomenon. We conducted a comprehensive investigation to identify the most sensitive window of exposure to TPTCl and to examine the effects of pre- and postnatal exposure on postnatal development in rats. The results on brain and gonadal aromatase activity obtained from offspring of dams exposed to 2 mg TPTCl/kg bw are reported here. Female and male offspring rats were exposed to 2 mg TPTCl/kg bw/d in utero from gestation day 6 through lactation until weaning on PND 21, or from gestation day 6 until termination at adulthood. Male offspring were sacrificed from PND 58 and female offspring at first estrus after PND 58. Pre- and postnatal TPT exposure clearly affected brain and gonadal aromatase activity in a sex-dependent fashion. While brain aromatase activity was significantly increased on PND 21 and at adulthood in female offspring, male offspring exhibited a significant decrease in brain aromatase activity only at adulthood. Ovarian aromatase activity was unaffected at both time points investigated. In contrast, testicular aromatase activity was significantly increased in males on PND 21 and significantly decreased at adulthood independent from the duration of treatment. The results of the present study confirm our previously reported observations regarding sex-dependent differences in sexual development after TPT exposure with the male rat being more susceptible to disturbances through this endocrine active compound than the female. We conclude that TPT administered during the particularly vulnerable period of development can affect aromatase activity in rats.

p,p'-DDE induces testicular apoptosis in prepubertal rats via the Fas/FasL pathway

1,1-Dichloro-2,2 bis(p-chlorophenyl) ethylene (p,p'-DDE), the major metabolite of 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (DDT), is a known persistent organic pollutant and male reproductive toxicant. It has antiandrogenic effect. However, the mechanism by which p,p'-DDE exposure causes male reproductive toxicity remains unknown. To elucidate the mechanism underpinning the testicular effects of p,p'-DDE, we sought to investigate Fas/FasL apoptotic pathway in the testis of prepubertal rats, including Fas, FasL, caspase-8, -3, and NF-kappaB. Animals were administered with different doses of p,p'-DDE (0, 20, 60, 100mg/kg b.wt) every other day by intraperitoneal injection for 10 days. The results indicated that p,p'-DDE exposure at over 20mg/kg b.wt showed the induction of apoptotic cell death. p,p'-DDE could induce increase in the MDA level, and decrease in SOD and GSH-Px activity. Significant elevations in the mRNA levels of Fas along with an increase in FasL, caspase-3, -8 were observed in 100mg/kg b.wt group. In protein level, p,p'-DDE could induce increase of FasL and reduction of procaspase-8. NF-kappaB p65 was activated by p,p'-DDE treatment in rat testis. In addition, the activities of caspase-3, -8 were increased in 100mg/kg b.wt group. Taken together, these results lead us to speculate that in vivo exposure to p,p'-DDE might induce testicular apoptosis in prepubertal rats through the Fas/FasL pathway.

p,p'-DDE induces apoptosis of rat Sertoli cells via a FasL-dependent pathway

One,1-dichloro-2,2 bis(p-chlorophenyl) ethylene (p,p′-DDE), the major metabolite of 2,2-bis(4-Chlorophenyl)-1,1,1-trichloroethane (DDT), is a known persistent organic pollutant and male reproductive toxicant. It has antiandrogenic effect. However, the mechanism by which p,p′-DDE exposure causes male reproductive toxicity remains unknown. In the present study, rat Sertoli cells were used to investigate the molecular mechanism involved in p,p′-DDE-induced toxicity in male reproductive system. The results indicated that p,p′-DDE exposure at over 30 μM showed the induction of apoptotic cell death. p,p′-DDE could induce increases in FasL mRNA and protein, which could be blocked by an antioxidant agent, N-acetyl-l-cysteine (NAC). In addition, caspase-3 and -8 were activated by p,p′-DDE treatment in these cells. The activation of NF-κB was enhanced with the increase of p,p′-DDE dose. Taken together, these results suggested that exposure to p,p′-DDE might induce apoptosis of rat Sertoli cells through a FasL-dependent pathway.

Effects of tributyltin on epididymal function and sperm maturation in mice

The effects of tributyltin (TBT) on sperm parameters and epididymal function were investigated following oral doses of 0.5, 5 and 50μg/kg every 3 days for 45 days to male KM mouse. The TBT-treated groups showed a significant decrease in sperm counts and a significant increase in sperm abnormality both in a dose-dependent manner. The expression of matrilysin (MMP7) transcript in epididymis of mice exposed to TBT was significantly decreased in 5 and 50μg/kg group. There was a dose-dependent decline trend in the acid phosphatase activity, which somewhat relates with the TBT-induced increase in sperm abnormality. Acrosin and lactate dehydrogenase-X isoenzyme (LDH-X) activities from the cauda epididymal spermatozoa showed a dose-dependent decrease in the TBT groups. The result indicates a suppression of essential sperm maturational processes that precede the penetration of the oocyte by the sperm, such as capacitation and acrosome reaction. These results suggest that TBT could cause a spermatotoxic effects, the decline of sperm count and quality caused by TBT suggests that this chemical could impair fertility in animals.

A broad-spectrum organophosphate pesticide O,O-dimethyl O-4-nitrophenyl phosphorothioate (methyl parathion) adversely affects the structure and function of male accessory reproductive organs in the rat

Methyl parathion (MP) is an organophosphate pesticide used in agriculture, but also illegally used to spray homes and businesses to control insects. The present study was designed to investigate adverse effects of MP on accessory reproductive organs. Male Wistar rats aged 13-14 weeks were treated and sacrificed as follows. Experiment 1: 0.0 (water vehicle), 1.75, 3.5 or 7mg/kg (i.p.) for 5 days and sacrificed on day 14; experiment 2: 0.0, 0.5 or 1mg/kg (i.p.) for 12 days and sacrificed on day 130; experiment 3: 0.0, 0.5 or 1mg/kg (i.p.) for 12 days and sacrificed on day 77; experiment 4: 0.0, 0.75 or 1.5mg/kg (i.p.) for 25 days and sacrificed on day 17 and experiment 5: 0.0 or 3.5mg/kg (p.o.) for 25 days and sacrificed on day 17, after the last exposure. The accessory reproductive organs were removed, weighed and processed for histopathological analysis. Structural qualitative changes such as epithelial cell morphology and luminal observations were carried out for each organ in all experiments. Epididymis of one side was homogenized and biochemical estimations of acid phosphatase (ACP), cholesterol, total protein, uric acid, and Vitamin C were conducted by calorimetric methods in experiments 4 and 5. In experiment 1 the organ weights did not change; in experiment 2, the epididymal weight increased (P<0.001); in experiment 3, the weights of ductus deferens decreased at 1mg/kg and that of seminal vesicle decreased at both dose-levels (P<0.001). In experiments 4 and 5, weights of epididymis and prostate decreased, whereas in experiment 5, weights of ductus deferens and seminal vesicle increased (P<0.05-0.001). The sperm density was normal in control, moderately decreased in experiment 1 at 3.5 and 7mg/kg; in experiment 2 at 1mg/kg, and in experiment 5 at 3.5mg/kg, and severely decreased in experiment 3 at 1mg/kg and in experiment 4 at both dose-levels. The epithelial necrosis and nuclear pyknosis were seen in experiments 1, 3, 4 and 5, whereas nuclear degeneration was seen in experiment 1 and 4 and germ cells in the lumina of epididymis were seen in experiment 4. The nuclear pyknosis in the ductus deferens was seen in all experiments, except at 1.75mg/kg in experiment 1 and at 0.5mg/kg in experiment 3. Brush border disruption in the ductus deferens was seen in experiments 1 and 4; sperms were seen in the lumen in experiment 1 at 7mg/kg, and in experiments 4 and 5. The vacuoles in the epithelium were seen in experiments 1 and 4 and immature germ cells were seen in the lumen in experiment 4. The ACP and Vitamin C levels decreased in experiment 4 at both dose-levels, and in experiment 5 all biochemical parameters tested found decreased (P<0.01-0.001). The present results indicate that MP affects the structure and function of accessory reproductive organs in the rat.

Effects of Perinatal Combined Exposure to 1,1-Dichloro-2,2 bis (p-chlorophenyl) ethylene and Tributyltin on Male Reproductive System

Prenatal or early postnatal exposure to some synthetic chemicals may affect the later reproductive system of the offspring. There may also be unique responses observed due to exposure to combinations of chemicals that are not observed when the chemicals are present individually. 1,1-Dichloro-2,2 bis (p-chlorophenyl) ethylene (p,p'-DDE) is a persistent metabolite of DDT and tributyltin (TBT) compounds are used primarily as antifouling agents, as they exert biocidal actions. p,p'-DDE and TBT are ubiquitously distributed in the environment. Oral p,p'-DDE and TBT intake through marine products is demonstrated to be high in Japan. Consequently, the foetus and neonate are supposed to be exposed much more to p,p'-DDE and TBT via the maternal body. Therefore, effects of perinatal exposure to p,p'-DDE and/or TBT on the reproductive system after maturation have been investigated in rat male offspring of dams orally administered 125 ppm p,p'-DDE (approximately 10 mg/kg) and 25 ppm TBT (approximately 2 mg/kg) during the gestational and lactational period. In this study, growth retardation attributed to TBT has sustained in rat male offspring after perinatal exposure. However, perinatal exposure to p,p'-DDE and TBT failed to affect the male reproductive organs and sperm parameters in matured male offspring.

AN ORGANOPHOSPHATE INSECTICIDE METHYL PARATHION (O- O- DIMETHYL O-4-NITROPHENYL PHOSPHOROTHIOATE) INDUCES CYTOTOXIC DAMAGE AND TUBULAR ATROPHY IN THE TESTIS DESPITE ELEVATED TESTOSTERONE LEVEL IN THE RAT

Methyl parathion (MP) is an organophosphate pesticide used in agriculture, although quite often illegally used indoors to contain insects. The present study was planned to investigate the effects of MP on rat testis. Adult male Wistar rats (13-14 weeks) were treated with MP as follows. Experiment 1-0, 1.75, 3.5 or 7 mg/kg i.p. for 5 days and sacrificed on Day 14; experiment 2 and 3- 0, 0.5, or 1 mg/kg i.p. for 12 days, and sacrificed on Days 130 and 77, respectively; experiment 4- 0, 0.75, or 1.5 mg/kg i.p. for 25 days, and sacrificed on Day 17; experiment 5- 0 or 3.5 mg/kg po for 25 days, and sacrificed on Day 17, after the last exposure. MP decreased the body weight and the testis weight in experiments 4 and 5 (p<0.05-0.001) due to decreased food intake and tubular atrophy respectively. MP increased the intra-testicular testosterone level and decreased the LH level in experiments 4 and 5. The seminiferous epithelium showed sloughing of germ cells, vacuoles, focal necrosis, and formation of multinucleated giant cells, cellular degeneration (nuclear pyknosis, halo appearance and shrinkage of nuclei) and tubular atrophy, especially in experiment 4. The degree of testicular damage was higher in experiment 4>5>1>3>2 indicating more effect of prolonged i.p. treatment. Homogenization-resistant spermatid count was decreased in experiments 1, 4 and 5, and MP also decreased the tubular diameter, and epithelial height (p<0.05-0.001). Incidences of stage XIV tubules, number of meiotic figures and elongating spermatids were also decreased, whereas the incidence of tubules showing epithelial sloughing increased (p<0.05-0.001). We conclude that MP is a reproductive toxicant in male rats which causes significant testicular damage in the testis.