Two-generation reproductive toxicity study of tributyltin chloride in male rats

Tributyltin chloride (TBTCL) induces cell injury via dysregulation of endoplasmic reticulum stress and autophagy in Leydig cells

Tributyltin chloride (TBTCL), a commonly used antiseptic substance, is commonly found in the environment. Human exposure to TBTCL through the consumption of contaminated seafood, fish, or drinking water has aroused concern. It is well-characterized that TBTCL has multiple detrimental effects on the male reproductive system. However, the potential cellular mechanisms are not fully elucidated. Here, we characterized molecular mechanisms of TBTCL-induced cell injury in Leydig cells, a critical supporter for spermatogenesis. We showed that TBTCL induces apoptosis and cell cycle arrest in TM3 mouse Leydig cells. RNA sequencing analyses revealed that endoplasmic reticulum (ER) stress and autophagy were potentially involved in TBTCL-induced cytotoxicity. We further showed that TBTCL causes ER stress and inhibited autophagy flux. Notably, the inhibition of ER stress attenuates not only TBTCL-induces autophagy flux inhibition but also apoptosis and cell cycle arrest. Meanwhile, the activation of autophagy alleviates, and inhibition of autophagy exaggerates TBTCL-induced apoptosis and cell cycle arrest flux. These results suggest that TBTCL-induced ER stress and autophagy flux inhibition contributed to apoptosis and cell cycle arrest in Leydig cells, providing novel understanding into the mechanisms of TBTCL-induced testis toxicity.

Tributyltin Exposure Is Associated With Recognition Memory Impairments, Alterations in Estrogen Receptor α Protein Levels, and Oxidative Stress in the Brain of Female Mice

Tributyltin (TBT) is a persistent organometallic pollutant widely used in several agricultural and industrial processes. TBT exposure is associated with various metabolic, reproductive, immune, and cardiovascular abnormalities. However, few studies have evaluated the effects of TBT on behavior. In the present study, we aimed to investigate whether TBT exposure results in oxidative, neuroendocrine, and behavioral alterations. TBT was administered to adult female mice (250, 500, or 750 ng/kg/day or veh for 14 days), and their recognition memory was assessed. We have also evaluated estrogen receptor (ER)α protein expression and oxidative stress (OS) in brain areas related to memory, as well as the correlation between them. A reduction in short- and long-term recognition memory (STM and LTM) performance, as well as in total exploration time was observed in TBT mice. Reduced ERα protein expression was observed in the prefrontal cortex (PFC) and hippocampus of TBT mice, while an increase in TBARS concentration was observed in the PFC of treated animals. Collectively, these data suggest that TBT exposure impairs recognition memory in female mice as a result of, at least in part, its toxicological effects on ERα expression and OS in specific brain areas related to memory.

Windows of sensitivity to toxic chemicals in the development of the endocrine system: an analysis of ATSDR's toxicological profile database

This review utilizes the robust database of literature contained in toxicological profiles developed by the Agency for Toxic Substances and Disease Registry. The aim was to use this database to identify developmental toxicity studies reporting alterations in hormone levels in the developing fetus and offspring and identify windows of sensitivity. We identified 74 oral exposure studies in rats that provided relevant information on 30 chemicals from 21 profiles. Most studies located provided information on thyroid hormones, with fewer studies on anterior pituitary, adrenal medulla, ovaries, and testes. No studies pertaining to hormones of the posterior pituitary, pancreas, or adrenal cortex were located. The results demonstrate that development of the endocrine system may be affected by exposure to environmental contaminants at many different points, including gestational and/or lactational exposure. Moreover, this review demonstrates the need for more developmental toxicity studies focused on the endocrine system and specifically alterations in hormone levels.

Effect of Trimethyltin chloride on proliferation and cell cycle of intestinal porcine epithelial cells

Trimethyltin chloride (TMT) is a highly toxic substance produced by organotin heat stabilizers in the synthesis of polyvinyl chloride (PVC) products. TMT is widely used in industry and agriculture. The aim of this study was to investigate the effects of TMT-induced cytotoxicity in intestinal porcine epithelial cells (IPEC-J2). Our study showed that TMT induced a decline in cell viability of IPEC-J2, caused cell shrinkage and rounded cell morphology, reduced the number of proliferating cells and the expression of proliferating cell nuclear antigen (PCNA), and increased lactate dehydrogenase (LDH) activity in cell supernatants. Simultaneously, TMT lowered the mRNA expression of Cyclin B1, and Cyclin D1, but increased P21 and P27 expression. The cell cycle progression was arrested from the G1 to the S phase. Furthermore, the mRNA expression of Bax/Bcl-2 ratio and the protein expression of cleaved Caspase-9 and cleaved Caspase-3 were significantly increased after TMT treatment, while the ratio of advanced apoptotic cells was elevated. These results indicated that TMT blocked the cell cycle, inhibited IPEC-J2 proliferation, and induced apoptosis.

Simultaneous Determination of Five Organotins in Tropical Fruits Using Modified QuEChERS Combined with Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry

A sensitive, confirmatory ultra-high performance liquid chromatography-tandem mass spectrometry based on modified QuEChERS was developed and validated to detect five organotin compounds (tributyltin chloride (TBT), triphenyltin chloride (TPT), trimethyltin chloride (TMT), azocyclotin and cyhexatin) in classical tropical fruits (mango, pineapple and banana). Fruits samples were ultrasonically extracted with methanol and subsequently purified by graphitized carbon black adsorbents. Five organotins were separated on a C18 column with the mobile phase of a mixture of methanol and 0.1% (v/v) aqueous formic acid, and detected by MS/MS under multiple reaction monitoring mode. The developed method was validated in terms of linearity, limit of detection (LOD), recovery and precision. Results were linear in their corresponding concentration ranges, with coefficients of determination (r) bigger than 0.999. The average LODs (S/N = 3) of the method for TBT, TPT, TMT, azocyclotin and cyhexatin were 1.3, 3.5, 3.2, 5.1 and 1.7 μg/kg, respectively. The average recoveries (n = 5) at three spiked levels (0.01, 0.1 and 0.2 mg/kg) ranged from 69 to 103% with relative standard deviations of 2.1-11.9%. The method is simple, effective, accurate and non-derivatized, and meets the routine monitoring requirements for trace organotins in tropical fruits.

Short term chronic toxicity of tributyltin on the testes of adult albino rats and the possible protective role of omega-3

The declining rate of male fertility is a growing concern. Tributyltin (TBT) is a well-known endocrine disruptor (ED), that induces imposex in female gastropods and is widely used in various industrial applications. The aim of this study was to evaluate the toxic effects of TBT on the testes of adult albino rats and the possible role of omega-3. Forty two adult male albino rats were divided into five groups; control group (Group I) and four experimental groups: omega-3 treated group, TBT treated group, TBT & omega-3 treated group and follow up group. At the end of the study, the rats were subjected to biochemical, histological, immunohistochemical staining for Ki-67 and seminal examinations. Our results clarfied that TBT induced a significant decrease in testosterone, FSH, LH and serum glutathione peroxidase levels and a significant increase in the serum Malondialdehyde as compared to the control group. Tributyltin induced disorganization and shrinkage of seminiferous tubules, apoptosis, cellular damage and marked reduction in the germinal epithelium. A significant decrease in the cell proliferation and arrested spermatogenesis were also detected. Seminal analysis of TBT group showed a significant affection of all parameters as compared to other groups. Omega-3 ameliorated all of these hazardous effects. Follow up group still showed toxic effects. In conclusion, TBT has a toxic effect on the testis. Increased testicular oxidative stress, cellular damage and arrest of spermatogenesis with attenuation in antioxidant defenses are all contributing factors. Omega-3 can protect against TBT induced reproductive toxicity.

Cardiotoxicity of environmental contaminant tributyltin involves myocyte oxidative stress and abnormal Ca2+ handling

Tributyltin (TBT) is an organotin environmental pollutant widely used as an agricultural and wood biocide and in antifouling paints. Countries began restricting TBT use in the 2000s, but their use continues in some agroindustrial processes. We studied the acute effect of TBT on cardiac function by analyzing myocardial contractility and Ca²⁺ handling. Cardiac contractility was evaluated in isolated papillary muscle and whole heart upon TBT exposure. Isolated ventricular myocytes were used to measure calcium (Ca²⁺) transients, sarcoplasmic reticulum (SR) Ca²⁺ content and SR Ca²⁺ leak (as Ca²⁺ sparks). Reactive oxygen species (ROS), as superoxide anion (O2^•-) was detected at intracellular and mitochondrial myocardium. TBT depressed cardiac contractility and relaxation in papillary muscle and intact whole heart. TBT increased cytosolic, mitochondrial ROS production and decreased mitochondrial membrane potential. In isolated cardiomyocytes TBT decreased both Ca²⁺ transients and SR Ca²⁺ content and increased diastolic SR Ca²⁺ leak. Decay of twitch and caffeine-induced Ca²⁺ transients were slowed by the presence of TBT. Dantrolene prevented and Tiron limited the reduction in SR Ca²⁺ content and transients. The environmental contaminant TBT causes cardiotoxicity within minutes, and may be considered hazardous to the mammalian heart. TBT acutely induced a negative inotropic effect in isolated papillary muscle and whole heart, increased arrhythmogenic SR Ca²⁺ leak leading to reduced SR Ca²⁺ content and reduced Ca²⁺ transients. TBT-induced myocardial ROS production, may destabilize the SR Ca²⁺ release channel RyR2 and reduce SR Ca²⁺ pump activity as key factors in the TBT-induced negative inotropic and lusitropic effects.

Insight into the endocrine disrupting effect and cell response to butyltin compounds in H295R cell: Evaluated with proteomics and bioinformatics analysis

The widespread use of organotin compounds (OTs) as biocides in antifouling paints and agricultural applications poses a serious threat to the ecosystem and humans. Butyltin compounds (BTs), especially tributyltin (TBT), are considered to be endocrine disrupting chemicals in marine organisms. The underlying mechanism of disrupting effects on mammals, however, has not been sufficiently investigated. To determine the effect and action of these biocides, the present study evaluated the effects of BTs on human adrenocortical carcinoma cells (H295R) with a focus on endocrine disrupting effect. Two-dimensional electrophoresis (2-DE) and subsequent mass finger printing were used to identify proteins expression profiles from the cells after exposure to 0.1μM BTs for 48h. In total, 89 protein spots showed altered expression in at least two treatment groups and 69 of these proteins were subsequently identified. Bioinformatic analysis of the proteins indicated that BTs involved in the regulation of hormone homeostasis, lipid metabolism, cell death, and energy production. IPA analysis revealed LXR/RXR (liver X receptor/retinoid X receptor) activation, FXR/RXR (farnesoid X receptor/retinoid X receptor) activation and fatty acid metabolism were the top three categories on which BTs acted and these systems play vital roles in sterol, glucose and lipid metabolism. The expression of LXR and FXR mRNA in H295R cells was stimulated by TBT, confirming the ability of TBT to activate this nuclear receptor. In summary, the differentially expressed proteins discovered in this study may participate in the toxic actions of BTs, and nuclear receptor activation and lipid metabolism may play important roles in such actions of BTs.

Tributyltin role on the serotonin and histamine receptors in human umbilical artery

Some studies in animals suggest that TBT may constitute a risk factor for cardiovascular diseases. Hence, the main purpose of this study was to investigate in human umbilical artery (HUA) the effect of TBT on vascular reactivity, manly in serotonin (5-HT) and histamine receptors. Using standard organ bath techniques, rings of HUA without endothelium were contracted by 5-HT and histamine. We also investigated the effect of TBT on the expression of the receptors using Real-time PCR. The results show that TBT short term effects include concentration-dependent relaxation. Moreover, at long term exposures, the arteries treated with 100 μM of TBT do not have contraction capacity when 5-HT is added, and the gene expression of 5-HT2A receptor decrease. Regarding histamine, it was demonstrated that TBT induces a concentration-dependent relaxation and the H1 gene expression levels decrease. In conclusion TBT modifies the activity and expression of 5-HT and histamine receptors.

Protective effects of fucoxanthin and fucoxanthinol against tributyltin-induced oxidative stress in HepG2 cells

Tributyltin (TBT) is a biocide extremely toxic to a wide range of organisms, which has been used for decades for industrial purposes. Fucoxanthin is a natural carotenoid that is isolated from seaweed, and fucoxanthinol is a major primary metabolite of fucoxanthin. Although fucoxanthin and fucoxanthinol have been reported to possess anti-oxidant activities in vitro, little is known as to whether they protect against TBT-induced oxidative stress in cultured cells. In the present study, the protective effect of fucoxanthin and fucoxanthinol against oxidative stress induced by TBT was investigated. The data showed that incubation of HepG2 cells with 0.2 μM TBT significantly increased cell apoptosis, whereas treatment with fucoxanthin or fucoxanthinol (3 μM) significantly recovered cell viability. In addition, fucoxanthinol treatment significantly decreased the intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) in HepG2 cells incubated with TBT. Moreover, fucoxanthin and fucoxanthinol markedly increased the expression level of Bcl-2/Bax. These results demonstrated that both fucoxanthin and fucoxanthinol effectively prevented cytotoxicity in HepG2 cells treated with TBT, and the protective effect was likely associated with decreased intracellular ROS and MDA and increased Bcl-2/Bax levels.

Organotins in Neuronal Damage, Brain Function, and Behavior: A Short Review

The consequences of exposure to environmental contaminants have shown significant effects on brain function and behavior in different experimental models. The endocrine-disrupting chemicals (EDC) present various classes of pollutants with potential neurotoxic actions, such as organotins (OTs). OTs have received special attention due to their toxic effects on the central nervous system, leading to abnormal mammalian neuroendocrine axis function. OTs are organometallic pollutants with a tin atom bound to one or more carbon atoms. OT exposure may occur through the food chain and/or contaminated water, since they have multiple applications in industry and agriculture. In addition, OTs have been used with few legal restrictions in the last decades, despite being highly toxic. In addition to their action as EDC, OTs can also cross the blood-brain barrier and show relevant neurotoxic effects, as observed in several animal model studies specifically involving the development of neurodegenerative processes, neuroinflammation, and oxidative stress. Thus, the aim of this short review is to summarize the toxic effects of the most common OT compounds, such as trimethyltin, tributyltin, triethyltin, and triphenyltin, on the brain with a focus on neuronal damage as a result of oxidative stress and neuroinflammation. We also aim to present evidence for the disruption of behavioral functions, neurotransmitters, and neuroendocrine pathways caused by OTs.

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.

Organotin Exposure and Vertebrate Reproduction: A Review

Organotin (OTs) compounds are organometallic compounds that are widely used in industry, such as in the manufacture of plastics, pesticides, paints, and others. OTs are released into the environment by anthropogenic actions, leading to contact with aquatic and terrestrial organisms that occur in animal feeding. Although OTs are degraded environmentally, reports have shown the effects of this contamination over the years because it can affect organisms of different trophic levels. OTs act as endocrine-disrupting chemicals (EDCs), which can lead to several abnormalities in organisms. In male animals, OTs decrease the weights of the testis and epididymis and reduce the spermatid count, among other dysfunctions. In female animals, OTs alter the weights of the ovaries and uteri and induce damage to the ovaries. In addition, OTs prevent fetal implantation and reduce mammalian pregnancy rates. OTs cross the placental barrier and accumulate in the placental and fetal tissues. Exposure to OTs in utero leads to the accumulation of lipid droplets in the Sertoli cells and gonocytes of male offspring in addition to inducing early puberty in females. In both genders, this damage is associated with the imbalance of sex hormones and the modulation of the hypothalamic-pituitary-gonadal axis. Here, we report that OTs act as reproductive disruptors in vertebrate studies; among the compounds are tetrabutyltin, tributyltin chloride, tributyltin acetate, triphenyltin chloride, triphenyltin hydroxide, dibutyltin chloride, dibutyltin dichloride, diphenyltin dichloride, monobutyltin, and azocyclotin.

Tributyltin: Advancing the Science on Assessing Endocrine Disruption with an Unconventional Endocrine-Disrupting Compound

Tributyltin (TBT) has been recognized as an endocrine disrupting chemical (EDC) for several decades. However, only in the last decade, was its primary endocrine mechanism of action (MeOA) elucidated-interactions with the nuclear retinoid-X receptor (RXR), peroxisome proliferator-activated receptor γ (PPARγ), and their heterodimers. This molecular initiating event (MIE) alters a range of reproductive, developmental, and metabolic pathways at the organism level. It is noteworthy that a variety of MeOAs have been proposed over the years for the observed endocrine-type effects of TBT; however, convincing data for the MIE was provided only recently and now several researchers have confirmed and refined the information on this MeOA. One of the most important lessons learned from years of research on TBT concerns apparent species sensitivity. Several aspects such as the rates of uptake and elimination, chemical potency, and metabolic capacity are all important for identifying the most sensitive species for a given chemical, including EDCs. For TBT, much of this was discovered by trial and error, hence important relationships and important sensitive taxa were not identified until several decades after its introduction to the environment. As recognized for many years, TBT-induced responses are known to occur at very low concentrations for molluscs, a fact that has more recently also been observed in fish species. This review explores the MeOA and effects of TBT in different species (aquatic molluscs and other invertebrates, fish, amphibians, birds, and mammals) according to the OECD Conceptual Framework for Endocrine Disruptor Testing and Assessment (CFEDTA). The information gathered on biological effects that are relevant for populations of aquatic animals was used to construct Species Sensitivity Distributions (SSDs) based on No Observed Effect Concentrations (NOECs) and Lowest Observed Effect Concentrations (LOECs). Fish appear at the lower end of these distributions, showing that they are as sensitive as molluscs, and for some species, even more sensitive. Concentrations in the range of 1 ng/L for water exposure (10 ng/g for whole-body burden) have been shown to elicit endocrine-type responses, whereas mortality occurs at water concentrations ten times higher. Current screening and assessment methodologies as compiled in the OECD CFEDTA are able to identify TBT as a potent endocrine disruptor with a high environmental risk for the original use pattern. If those approaches had been available when TBT was introduced to the market, it is likely that its use would have been regulated sooner, thus avoiding the detrimental effects on marine gastropod populations and communities as documented over several decades.

Tributyltin induces disruption of microfilament in HL7702 cells via MAPK-mediated hyperphosphorylation of VASP

Tributyltin (TBT) has been widely used for various industrial purposes, and it has toxic effects on multiple organs and tissues. Previous studies have found that TBT could induce cytoskeletal disruption, especially of the actin filaments. However, the underlying mechanisms remain unclear. The aim of the present study was to determine whether TBT could induce microfilament disruption using HL7702 cells and then to assess for the total levels of various microfilament-associated proteins; finally, the involvement of the MAPK pathway was investigated. The results showed that after TBT treatment, F-actin began to depolymerize and lost its characteristic filamentous structure. The protein levels of Ezrin and Cofilin remained unchanged, the actin-related protein (ARP) 2/3 levels decreased slightly, and the vasodilator-stimulated phosphoprotein (VASP) decreased dramatically. However, the phosphorylation levels of VASP increased 2.5-fold, and the ratio of phosphorylated-VASP/unphosphorylated-VASP increased 31-fold. The mitogen-activated protein kinases (MAPKs) ERK and JNK were discovered to be activated. Inhibition of ERK and JNK not only largely diminished the TBT-induced hyperphosphorylation of VASP but also recovered the cellular morphology and rescued the cells from death. In summary, this study demonstrates that TBT-induced disruption of actin filaments is caused by the hyperphosphorylation of VASP through MAPK pathways. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1530-1538, 2016.

Toxicogenomic analysis identifies the apoptotic pathway as the main cause of hepatotoxicity induced by tributyltin

Tributyltin (TBT) is one of the most widely used organotin biocides, which has severe endocrine-disrupting effects on marine species and mammals. Given that TBT accumulates at higher levels in the liver than in any other organ, and it acts mainly as a hepatotoxic agent, it is important to clearly delineate the hepatotoxicity of TBT. However, most of the available studies on TBT have focused on observations at the cellular level, while studies at the level of genes and proteins are limited; therefore, the molecular mechanisms of TBT-induced hepatotoxicity remains largely unclear. In the present study, we applied a toxicogenomic approach to investigate the effects of TBT on gene expression in the human normal liver cell line HL7702. Gene expression profiling identified the apoptotic pathway as the major cause of hepatotoxicity induced by TBT. Flow cytometry assays confirmed that medium- and high-dose TBT treatments significantly increased the number of apoptotic cells, and more cells underwent late apoptosis in the high-dose TBT group. The genes encoding heat shock proteins (HSPs), kinases and tumor necrosis factor receptors mediated TBT-induced apoptosis. These findings revealed novel molecular mechanisms of TBT-induced hepatotoxicity, and the current microarray data may also provide clues for future studies.

WITHDRAWN: The potential contribution of endocrine disrupting chemicals to acne

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Perinatal exposure to low doses of tributyltin chloride reduces sperm count and quality in mice

Exposure to endocrine disruptors (EDs) during early development might lead to adverse health outcomes later in life. Tributyltin (TBT), a proven ED, is widely used in consumer goods and industrial products. Herein we demonstrate the effects of low doses of tributyltin chloride (TBTCl) on reproduction of male KM mice. Pregnant mice were administered by gavage with 0, 1, 10, or 100 μg TBTCl/kg body weight/day from day 6 of pregnancy through the period of lactation. TBTCl dramatically decreased sperm counts and motility on postnatal days (PNDs) 49 and 152. Meanwhile, a significant increase in sperm abnormality was observed in exposed mice on PND 49, but comparable to that in the control on PND 152. The histopathological analysis of testes of treated animals showed a dose-dependent increase in sloughing of germ cells in seminiferous tubules. Mice treated with 10 μg TBTCl/kg exhibited decreased intratesticular 17β-estradiol (E2) levels on PND 49, and then followed by an obvious recovery on PND 152. While, no significant differences in serum E2, testosterone (T) levels and intratesticular T levels were detectable between control and TBTCl-exposed offspring at the sacrifice. These results suggest that perinatal TBTCl exposure is implicated in causing long lasting alterations in male reproductive system and these changes may persist far into adulthood.

A high throughput screening system for predicting chemically-induced reproductive organ deformities

There is a great need for alternative testing methods for reproductive toxicants that are practical, fast, cost-effective and easy to interpret. Previously we followed a pragmatic approach using readily available tests, which was successful in predicting reproductive toxicity of chemicals [13]. This initial battery still contained apical tests and is fairly complex and low in its throughput. The current study aimed to simplify this screening battery using a mechanistic approach and a panel of high throughput CALUX reporter gene assays. A mechanistic approach was taken to validate this high throughput test battery. To this end it was challenged with two preselected sets of chemicals addressing two major apical effect classes relevant in reproductive toxicity. We found selectivity in this battery in that 82% of the compounds inducing reproductive organ deformities were predicted correctly, while for compounds inducing neural tube defects this was the case in 47% only. This is consistent with the mechanisms of toxicity covered in the battery. The most informative assays in the battery were ERalpha CALUX to measure estrogenicity and the AR-anti CALUX assay to measure androgen receptor antagonism.

Ultrastructural changes during spermatogenesis, biochemical and hormonal evidences of testicular toxicity caused by TBT in freshwater prawn Macrobrachium rosenbergii (De Man, 1879)

The present investigation documents the impact of tributyltin (TBT) on the ultrastructural variation of spermatogenesis in freshwater prawn Macrobrachium rosenbergii. The environmentally realistic concentration of TBT can cause damages to the endocrine and reproductive physiology of crustaceans. In this context, three concentrations viz. 10, 100, and 1000 ng/L were selected and exposed to prawns for 90 days. The TBT exposed prawn exhibited decrease the reproductive activity as evidenced by sperm count and sperm length compared to control. Histopathological results revealed the retarded testicular development, abnormal structure of seminiferous tubule, decrease in the concentration of spermatozoa, diminution of seminiferous tubule membrane, abundance of spermatocytes and vacuolation in testis of treated prawns. Ultrastructural study also confirmed the impairment of spermatogenesis in treated prawns. Furthermore, radioimmunoassay (RIA) clearly documented the reduction of testosterone level in TBT exposed groups. Thus, TBT substantially reduced the level of male sex hormone as well as biochemical constituents which ultimately led to impairment of spermatogenesis in the freshwater male prawn M. rosenbergii.

Disruption of thyroid hormone functions by low dose exposure of tributyltin: an in vitro and in vivo approach

Triorganotins, such as tributyltin chloride (TBTCl), are environmental contaminants that are commonly found in the antifouling paints used in ships and other vessels. The importance of TBTCl as an endocrine-disrupting chemical (EDC) in different animal models is well known; however, its adverse effects on the thyroid gland are less understood. Hence, in the present study, we aimed to evaluate the thyroid-disrupting effects of this chemical using both in vitro and in vivo approaches. We used HepG2 hepatocarcinoma cells for the in vitro studies, as they are a thyroid hormone receptor (TR)-positive and thyroid responsive cell line. For the in vivo studies, Swiss albino male mice were exposed to three doses of TBTCl (0.5, 5 and 50μg/kg/day) for 45days. TBTCl showed a hypo-thyroidal effect in vivo. Low-dose treatment of TBTCl exposure markedly decreased the serum thyroid hormone levels via the down-regulation of the thyroid peroxidase (TPO) and thyroglobulin (Tg) genes by 40% and 25%, respectively, while augmenting the thyroid stimulating hormone (TSH) levels. Thyroid-stimulating hormone receptor (TSHR) expression was up-regulated in the thyroid glands of treated mice by 6.6-fold relative to vehicle-treated mice (p<0.05). In the transient transactivation assays, TBTCl suppressed T3 mediated transcriptional activity in a dose-dependent manner. In addition, TBTCl was found to decrease the expression of TR. The present study thus indicates that low concentrations of TBTCl suppress TR transcription by disrupting the physiological concentrations of T3/T4, followed by the recruitment of NCoR to TR, providing a novel insight into the thyroid hormone-disrupting effects of this chemical.

De novo transcriptomic profile in the gonadal tissues of the intertidal whelk Reishia clavigera

The intertidal whelk Reishia clavigera (formerly named as Thais clavigera) is one of the most sensitive species to organotin-associated imposex. However, the limited information on mRNA transcriptome of the species has restricted the molecular investigation on such endocrine disruption. By means of Illumina sequencing, we obtained a global de novo transcriptome from the gonadal tissues of both male and female R. clavigera, with 197,324 assembled transcripts and 151,684 condensed non-redundant transcripts. Blast hit results from the NCBI's non-redundant molluscan database showed that 28,948 transcripts were successfully annotated with significant matches at an e-value of ⩽1e(-6). Among them, 1108 transcripts were assigned a well-defined gene ontology term. As the first transcriptomic study on the gonadal tissues of R. clavigera, this study has enhanced the information of mRNA transcriptome on this species and will thus facilitate mechanistic studies of chemical contaminants (e.g., organotins) on this common biomonitor species.

Effect of Lactational Exposure to Tributyltin Chloride on Innate Immunodefenses in the F1 Generation in Mice

We examined the effect of lactational exposure to tributyltin on innate immunodefenses in the F1 generation using in vivo and in vitro experiments. Pregnant C57BL/6 mice were given drinking water containing 0, 15, or 50 microg/ml of tributyltin chloride (TBTCl) from parturition to weaning. At weaning time, offspring were inoculated with Escherichia coli K-12, and bacterial clearances from the peritoneal cavity and spleen were examined. In vivo infection experiments indicated that bacterial clearance was significantly depressed in offspring breast-fed by dams exposed to 15 microg/ml of TBTCl (15 ppm F1), but not in offspring by dams exposed to 50 microg/ml of TBTCl (50 ppm F1). In vitro functional assays revealed that the killing activity of neutrophils decreased significantly in 15 ppm F1, but not in 50 ppm F1. We suggest that lactational exposure to TBT impairs innate immunodefenses in the F1 generation against non-pathogenic bacterial infection.

Chronic exposure to tributyltin chloride induces pancreatic islet cell apoptosis and disrupts glucose homeostasis in male mice

It has been reported that organotin compounds such as triphenyltin or tributyltin (TBT) induce diabetes and insulin resistance. However, histopathological effects of organotin compounds on the Islets of Langerhans and exocrine pancreas are still unclear. In the present study, male KM mice were orally administered with TBT (0.5, 5, and 50 μg/kg) once every 3 days. The fasting plasma glucose levels significantly elevated, and the levels of serum insulin or glucagon decreased in the animals treated with TBT for 60 days. In animals treated for 45 days, the number of apoptotic cells in the islets and exocrine pancreas was elevated in a dose-dependent manner. The percentage of proliferating (PCNA-positive) cells was decreased in the islets, while it was increased in exocrine acinar cells. Immunohistochemistry analysis showed that estrogen receptor (ER) and androgen receptor (AR) were present in vascular endothelium, ductal cells, and islet cells, but absent from pancreatic exocrine cells. TBT exposure decreased the production of estradiol and triiodothyronine and elevated the concentration of testosterone, and resulted in a decrease of ERα expression and an elevation of AR in the pancreas measured by Western boltting. The results suggested that TBT inhibited the proliferation and induced the apoptosis of islet cells via multipathways, causing a decrease of relative islet area in the animals treated for 60 days, which could result in a disruption of glucose homeostasis. The different presence of ERs and AR between the islets and exocrine pancreas might be one of reasons causing different effects on cell proliferation.

Early cellular responses against tributyltin chloride exposure in primary cultures derived from various brain regions

Tributyltin (TBT) is a potent biocide and commonly used in various industrial sectors. Humans are mainly exposed through the food chain. We have previously demonstrated tin accumulation in brain following TBT-chloride (TBTC) exposure. In this study, effect of TBTC on dissociated cells from different brain regions was evaluated. Cytotoxicity assay (MTT), mode of cell death (Annexin V/PI assay), oxidative stress parameters (ROS and lipid peroxidation), reducing power of the cell (GSH), mitochondrial membrane potential (MMP) and intracellular Ca(2+) were evaluated to ascertain the effect of TBTC. Expression of glial fibrillary acidic protein (GFAP) was measured to understand the effect on astroglial cells. TBTC as low as 30 nM was found to reduce GSH levels, whereas higher doses of 300 and 3000 nM induced ROS generation and marked loss in cell viability mainly through apoptosis. Striatum showed higher susceptibility than other regions, which may have further implications on various neurological aspects.

Stimulation of estradiol biosynthesis by tributyltin in rat hippocampal slices

Hippocampal functions are influenced by steroid hormones, such as testosterone and estradiol. It has been demonstrated that hippocampus-derived steroid hormones play important roles in neuronal protection and synapse formation. Our research groups have demonstrated that estradiol is de novo synthesized in the rat hippocampus. However, the mechanism(s) regulating this synthesis remains unclear. It has been reported that tributyltin, an environmental pollutant, binds to the retinoid X receptor (RXR) and modifies estrogen synthesis in human granulosa-like tumor cells. This compound can penetrate the blood brain barrier, and tends to accumulate in the brain. Based on these facts, we hypothesized that tributyltin could influence the hippocampal estradiol synthesis. A concentration of 0.1 μM tributyltin induced an increase in the mRNA content of P450(17α) and P450arom in hippocampal slices, as determined using real-time PCR. The transcript levels of other steroidogenic enzymes and a steroidogenic acute regulatory protein were not affected. The estradiol level in rat hippocampal slices was subsequently determined using a radioimmunoassay. We found that the estradiol synthesis was stimulated by ∼2-fold following a 48-h treatment with 0.1 μM tributyltin, and this was accompanied by transcriptional activation of P450(17α) and P450arom. Tributyltin stimulated de novo hippocampal estradiol synthesis by modifying the transcription of specific steroidogenic enzymes.

Tributyltin chloride induced testicular toxicity by JNK and p38 activation, redox imbalance and cell death in sertoli-germ cell co-culture

The widespread use of tributyltin (TBT) as biocides in antifouling paints and agricultural chemicals has led to environmental and marine pollution. Human exposure occurs mainly through TBT contaminated seafood and drinking water. It is a well known endocrine disruptor in mammals, but its molecular mechanism in testicular damage is largely unexplored. This study was therefore, designed to ascertain effects of tributyltin chloride (TBTC) on sertoli-germ cell co-culture in ex-vivo and in the testicular tissue in-vivo conditions. An initial Ca(2+) rise followed by ROS generation and glutathione depletion resulted in oxidative damage and cell death. We observed p38 and JNK phosphorylation, stress proteins (Nrf2, MT and GST) induction and mitochondrial depolarization leading to caspase-3 activation. Prevention of TBTC reduced cell survival and cell death by Ca(2+) inhibitors and free radical scavengers specify definitive role of Ca(2+) and ROS. Sertoli cells were found to be more severely affected which in turn can hamper germ cells functionality. TBTC exposure in-vivo resulted in increased tin content in the testis with enhanced Evans blue leakage into the testicular tissue indicating blood-testis barrier disruption. Tesmin levels were significantly diminished and histopathological studies revealed marked tissue damage. Our data collectively indicates the toxic manifestations of TBTC on the male reproductive system and the mechanisms involved.

Association of placenta organotin concentrations with congenital cryptorchidism and reproductive hormone levels in 280 newborn boys from Denmark and Finland

STUDY QUESTION

Is the placental burden of organotin compounds (OTCs) associated with congenital cryptorchidism in infant offspring from Finland and Denmark?

SUMMARY ANSWER

Increasing concentrations of OTCs had a negative association with cryptorchidism in Finland, whereas a positive association was found in Denmark.

WHAT IS KNOWN ALREADY

The rapid increase in the prevalence of cryptorchidism suggests that environmental factors, such as endocrine disruptors, may be involved. OTCs are endocrine disruptors at very low concentrations due to activation of the retinoid X receptor (RXR).

STUDY DESIGN, SIZE, DURATION

Between the years 1997 and 2001, placentas from mothers of cryptorchid boys and from healthy controls were collected from Denmark (39 cases, 129 controls) and Finland (56 cases, 56 controls). In Denmark 33 and 6 boys, and in Finland 22 and 34 boys had mild or severe cryptorchidism, respectively. The association between concentrations of four OTCs [monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT) and triphenyltin (TPhT)] and case-control status was estimated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In both countries, placenta samples were selected from larger cohorts. In Finland placenta samples were collected from boys with cryptorchidism at birth and matched controls (nested case-control design). Matching criteria were parity, maternal smoking (yes/no), diabetes (yes/no), gestational age (±7 days) and date of birth (±14 days). Numbers of controls per case was 1. In Denmark, all available placentas from cryptorchid boys were chosen and control placentas were selected randomly from the total Danish cohort (case-cohort design). The average number of controls per case was 3.3. OTCs in placenta samples were analysed with liquid extraction, ethylation and gas chromatography-mass spectrometry determination and coded by country-specific tertiles.

MAIN RESULTS AND THE ROLE OF CHANCE

Generally, the concentrations of OTCs were very low. For most analytes, a large proportion of samples (29-96% depending on the country and case-control status) had OTC concentrations below the limit of quantification (LOQ). As an exception, the concentration of TBT was >LOQ in 99% of Finnish placentas. The mean concentrations of DBT and TBT were 1.5 and 7 times higher in Finland than in Denmark, respectively. For DBT in Danish placentas, the odds ratio (OR) for cryptorchidism in the second tertile (0.10-0.14 ng/g) when compared with the first tertile (<0.10 ng/g, <LOQ) was 3.13 (95% CI 1.19-8.26) and the OR for the third tertile (≥0.15 ng/g) when compared with the first tertile was 4.01 (95% CI 1.42-11.33). For TBT in Finnish placentas, the OR for cryptorchidism in the second tertile (0.10-0.39 ng/g) when compared with the first tertile (<0.1 ng/g) was 0.61 (95% CI 0.18-2.01) and the OR for the third tertile (≥0.40 ng/g) when compared with the first tertile was 0.13 (95% CI 0.03-0.54).

LIMITATIONS, REASONS FOR CAUTION

The main limitation of the study was the relatively small number of mother-boy pairs that limits the extrapolation of the study results to the general population. Also misclassification of exposure is a reason for caution for two reasons: because the concentrations of most OTCs were below or only barely above the LOQ in a large proportion of samples and because it is not known how well OTCs measured from placenta represent exposure at the time window that is relevant for cryptorchidism occurrence.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to measure the concentrations of OTCs from human placenta samples, and to associate these concentrations to cryptorchidism. As opposite results were obtained with regard to OTC concentration in placenta and cryptorchidism status in Finland and Denmark, and no mechanism is known at the moment by which OTCs could affect testicular descent, these results cannot be generalized to other populations. However, some animal tests described in the literature show opposite effects of OTCs on fat deposition at different ranges of exposure. It is also clearly shown in the literature that TBT has an impact on sexual development of gastropods through RXR. As TBT is known to activate human RXR, further laboratory studies should be designed to explore the potential impact of TBT on male sexual development.

Perinatal exposure to low doses of tributyltin chloride advances puberty and affects patterns of estrous cyclicity in female mice

Tributyltin (TBT), a proven endocrine-disrupting chemical, is well known to induce imposex in female gastropods. Herein we demonstrate the effects of low doses of tributyltin chloride (TBTCl) on the female offspring of KM mice. Pregnant mice were administered by gavage with 0, 1, 10, or 100 μg TBTCl/kg body weight/day from day 6 of pregnancy through the period of lactation. TBTCl dramatically advanced the age of onset of vaginal opening (VO) and first vaginal estrus, and reduced body weights at VO and first estrus. Furthermore, perinatal treatment with TBTCl significantly reduced the number of days between VO and first estrus. In addition, female offspring from dams exposed to 10 and 100 μg kg(-1) TBTCl exhibited altered patterns of estrous cyclicity in adulthood. In conclusion, perinatal exposure to low doses TBTCl result in early puberty and impaired estrous cyclicity in female mice, which suggest that TBTCl might act as an estrogen agonist or/and a disruptor on hypothalamic-pituitary function in the present study.

Effects of perinatal exposure to low doses of tributyltin chloride on pregnancy outcome and postnatal development in mouse offspring

Tributyltin (TBT), an endocrine-disrupting chemical, is well known to induce imposex in female gastropods. In this study, we assessed the effects of low doses of tributyltin chloride (TBTCl) on dams and their offspring. Pregnant mice were administered by gavage with 0, 1, 10, or 100 μg TBTCl/kg body weight/day from day 6 of pregnancy through the period of lactation. There were no TBT treatment-related deaths or clinical signs of toxicity for dams, and no treatment-related effects on body weight, litter sizes, gestational length of dams, and sex ratio, lactational body weight, postnatal survival, age at eruption of incisors, and eye opening of pups. However, at 100 μg/kg, TBTCl retarded the testes descent of male offspring. Behavioral tests showed a significant delay in cliff-drop aversion response in offspring of 10 and 100 μg/kg groups, but no significant difference in the righting reflex between control and TBT-exposed offspring was detectable. These results indicate that neurobehavioral toxicity seems to be one sensitive indicator to assess the risk of low doses of TBT.

Tributyltin impairs the coronary vasodilation induced by 17β-estradiol in isolated rat heart

Triorganotins, such as tributyltin (TBT), are environmental contaminants that are commonly used as antifouling agents for boats. However, TBT is also known to alter mammalian reproductive functions. Although the female sex hormones are primarily involved in the regulation of reproductive functions, 17β-estradiol also protects against cardiovascular diseases, in that this hormone reduces the incidence of coronary artery disease via coronary vasodilation. The aim of this study was to examine the influence of 100 ng/kg TBT administered daily by oral gavage for 15 d on coronary functions in female Wistar rats. Findings were correlated with changes in sex steroids concentrations. Tributyltin significantly increased the baseline coronary perfusion pressure and impaired vasodilation induced by 17β-estradiol. In addition, TBT markedly decreased serum 17β-estradiol levels accompanied by a significant rise in serum progesterone levels. Tributyltin elevated collagen deposition in the heart interstitium and number of mast cells proximate to the cardiac vessels. There was a positive correlation between the increase in coronary perfusion pressure and incidence of cardiac hypertrophy. In addition, TBT induced endothelium denudation (scanning electron microscopy) and accumulation of platelets. Moreover, TBT impaired coronary vascular reactivity to estradiol (at least in part), resulting in endothelial denudation, enhanced collagen deposition and elevated number of mast cells. Taken together, the present results demonstrate that TBT exposure may be a potential risk factor for cardiovascular disorders in rats.

Tributyltin impairs the reproductive cycle in female rats

Triorganotins are environmental contaminants, commonly used in antifouling agents for boats, that bioaccumulate and thus are found in mammals and humans due to ingestion of contaminated seafood diets. The importance of triorganotins as environmental endocrine disruptors and consequent reproductive toxicity in different animal models is well known; however, the adverse effects on reproductive cycle are less well understood. The potential reproductive toxicity of tributyltin (TBT) on regular reproductive cycling of female rats was examined. Wistar female rats (12 wk old, weighing approximately 230 g) were divided into two groups: control (vehicle, ethanol 0.4%) and tributyltin (100 ng/kg/d, 7 d/wk, for 16 d by gavage). Tributyltin significantly decreased the cycle regularity (%), duration of the reproductive cycle, the proestrus and diestrus phases, and number of epithelial cell in proestrus phase. TBT also increased the duration of metestrus and the number of cornified cells in this phase. Ovary weight and serum 17β-estradiol levels decreased markedly, accompanied by a significant increase in progesterone levels. Histological analysis showed apoptotic cells in corpus luteum and granulosa cells layer, with cystic follicles after TBT exposure. Tributyltin also elevated number of atretic follicles and corpoa lutea. The micronucleus (MN) test, using Chinese hamster ovary cells, demonstrated a concentration-dependent mutagenic effect of TBT, and at 2.0 × 10(-2)ng/ml most of the cells were nonviable. The toxic potential of TBT over the reproductive cycle may be attributed to changes found in the ovarian weight, unbalanced levels of sexual female hormones, and number of ovarian follicles and corpora lutea.

Endocrine disruptors: from endocrine to metabolic disruption

Synthetic chemicals currently used in a variety of industrial and agricultural applications are leading to widespread contamination of the environment. Even though the intended uses of pesticides, plasticizers, antimicrobials, and flame retardants are beneficial, effects on human health are a global concern. These so-called endocrine-disrupting chemicals (EDCs) can disrupt hormonal balance and result in developmental and reproductive abnormalities. New in vitro, in vivo, and epidemiological studies link human EDC exposure with obesity, metabolic syndrome, and type 2 diabetes. Here we review the main chemical compounds that may contribute to metabolic disruption. We then present their demonstrated or suggested mechanisms of action with respect to nuclear receptor signaling. Finally, we discuss the difficulties of fairly assessing the risks linked to EDC exposure, including developmental exposure, problems of high- and low-dose exposure, and the complexity of current chemical environments.

Peripubertal exposure to low doses of tributyltin chloride affects the homeostasis of serum T, E2, LH, and body weight of male mice

Previous studies have shown that tributyltin could act as an endocrine disruptor in mammals. However, the data on the low-dose effect of tributyltin in animals are still lacking. The objective of this study was to demonstrate the endocrine disruption induced by low levels of tributyltin chloride (TBTCl) in male KM mice. The animals were treated with 0.05 or 0.5 mg TBTCl/kg body weight/3 days from postnatal days (PNDs) 24 to 45, and killed on PNDs 49 and 84, respectively. Mice treated with 0.5 mg TBTCl/kg exhibited decreased serum and intratesticular testosterone (T) levels on PND 49 and then followed by an obvious recovery on PND 84. Furthermore, mice treated with 0.05 mg TBTCl/kg showed reduced serum 17β-estradiol (E2) levels on PND 49. However, treatments with TBTCl resulted in a dose-dependent increase in serum E2 concentration of the mice on PND 84. Administration of TBTCl also decreased levels of serum luteinizing hormone and intratesticular E2 on PND 84. In addition, mice exposed to 0.05 mg/kg TBTCl exhibited an increase in body weight in the late stage of the experiment. These results indicate that treatment with low doses of TBTCl could disturb hormone homeostasis and body weight gain in rodents, and exposure to different levels of TBTCl might have different effects on changing some physiologic parameters.

Testicular spermiation failure in rats exposed prenatally to 3,3',4,4',5-pentachlorobiphenyl

Testicular spermatogenesis was studied in 7-, 10-, 13- and 17-week-old Sprague-Dawley rats whose dams had been administered intragastrically with 2.5, 25, or 250 ng of 3,3',4,4',5-pentachlorobiphenyl (PCB126) or vehicle on days 13-19 of gestation. The 250 ng groups among the 7-, 10- and 13-week-old offspring showed significant inhibition of mature spermatid release (spermiation), but 17-week-old offspring did not show this. These alterations were not observed in other PCB126 and vehicle groups, and no germ cell or Sertoli cell degeneration were observed in any group. Spermiation failure at puberty appeared in those rats born to dams exposed 250 ng/kg PCB126 on days 13-19 of gestation was reversible change that recovered at adulthood. Because the serum testosterone, luteinizing hormone and follicle-stimulating hormone concentrations were similar in the PCB126 and vehicle groups, a direct endocrine cause for the observed effects was unlikely.

Oestrogens and spermatogenesis

The role of oestrogens in male reproductive tract physiology has for a long time been a subject of debate. The testis produces significant amounts of oestrogenic hormones, via aromatase, and oestrogen receptors (ERs)alpha (ESR1) and ERbeta (ESR2) are selectively expressed in cells of the testis as well as the epididymal epithelium, depending upon species. This review summarizes the current knowledge concerning the presence and activity of aromatase and ERs in testis and sperm and the potential roles that oestrogens may have in mammalian spermatogenesis. Data show that physiology of the male gonad is in part under the control of a balance of androgens and oestrogens, with aromatase serving as a modulator.

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.

Postnatal development and resistance to Plasmodium yoelii infection of mice prenatally exposed to triphenyltin hydroxide

In this study, we evaluated the effects of prenatal exposure to triphenyltin hydroxide (TPTH) on the postnatal development of Swiss Webster mice. Females were treated by gavage (0, 7.5 15 and 30 mg TPTH/kg/day) on days 6-17 of gestation. After birth, the progeny was examined for deaths, body weight gain and appearance of developmental landmarks. On postnatal day 50, one male and one female of each litter were inoculated with Plasmodium yoelii and the time-course of infection was monitored. TPTH was embryolethal at doses > or =15 mg/kg/day. Body weight at birth was decreased, but no alteration of pup body weight was observed after postnatal day 5. Except for an advancement of incisor eruption in the group treated with 15 mg/kg/day, no alteration of somatic development was noted. A shorter latency to peak parasitemia and a reduced malaria-induced spleen enlargement were observed in mice prenatally exposed to TPTH. In conclusion, prenatal exposure to TPTH at doses > or =15 mg/kg enhanced neonatal lethality, reduced pup birth weight and interfered with the response to infection with P. yoelii in adulthood.

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.

Inhibitory effect of tributyltin on expression of steroidogenic enzymes in mouse testis

Tributyltin (TBT) is known to disrupt the development of reproductive organs, thereby reducing fertility. The aim of this study was to evaluate the acute toxicity of TBT on the testicular development and steroid hormone production. Immature (3-week-old) male mice were given a single administration of 25, 50, or 100 mg/kg of TBT by oral gavage. Lumen formation in seminiferous tubule was remarkably delayed, and the number of apoptotic germ cells found inside the tubules was increased in the TBT-exposed animals, whereas no apoptotic signal was observed in interstitial Leydig cells. Reduced serum testosterone concentration and down-regulated expressions of the mRNAs for cholesterol side-chain cleavage enzyme (P450scc), 17alpha -hydroxylase/C(17-20) lyase (P450(17alpha)), 3beta -hydroxysteroid-dehydrogenase (3beta -HSD), and 17beta -hydroxysteroid-dehydrogenase (17beta -HSD) were also observed after TBT exposure. Altogether, these findings demonstrate that exposure to TBT is associated with induced apoptosis of testicular germ cells and inhibition of steroidogenesis by reduction in the expression of steroidogenic enzymes in interstitial Leydig cells. These adverse effects of TBT would cause serious defects in testicular development and function.

Organotin speciation and tissue distribution in rat dams, fetuses, and neonates following oral administration of tributyltin chloride

Tributyltin (TBT) is a biocide that contaminates human foodstuffs, especially shellfish. TBT is an endocrine disrupter, producing imposex in several marine gastropods. Previous studies showed that oral dosing of rat dams with TBT chloride leads to abnormal fetal and postnatal development. In this study, the tissue distribution and speciation of organotins in tissues were examined in dams, fetuses, and neonates following dosing of rat dams commencing on gestational day (GD) 8 by oral gavage with TBT in olive oil at 0, 0.25, 2.5, or 10 mg/kg body weight (BW)/d. Dams' body weights were significantly reduced by the 10-mg/kg BW/d TBT treatment. At GD20, there were no significant effects of any TBT treatment on pup weights, litter size, sex ratio, or tissue weights. However, at postnatal day (PND) 6 and 12, neonatal pup weights were reduced by the 10-mg/kg BW/d TBT treatment but tissue weights were unaffected, except for the liver weight of female pups, which was reduced by the 10-mg/kg BW/d TBT treatment. Tissues harvested on GD20 and PND6 and PND12 were extracted for determination of organotins by gas chromatography-atomic emission detection (GC-AED). In most tissues, TBT and its metabolite dibutyltin (DBT) were evident but monobutyltin (MBT) was rarely measured above the detection limit. The livers and brains of fetuses contained TBT and DBT at levels that were approximately 50% of the equivalent tissues in the dams. Furthermore, these tissues appeared to preferentially absorb/retain organotins, since the concentrations were greater than were found for the total loading in whole pups. The placenta also contained relatively large quantities of TBT and DBT. Postnatally, the TBT levels in pups decreased markedly, a probable consequence of the extremely low levels of organotins in rat milk. However, DBT levels in pups livers and brains were maintained, probably due to metabolism of TBT to DBT. Similarly, while dams' spleens contained significant quantities of organotins, the pups' spleens contained smaller quantities, and these decreased rapidly between PND6 and PND12. These results show that organotins cross the placenta and accumulate in fetal tissues but that during lactation, the pups would receive minimal organotins through the milk and during this period, the levels of TBT in pups' tissues decreases rapidly. Consequently, fetuses would be at greater risk of the adverse effects of TBT, but due to the lack of transfer through milk, the risk would be reduced during the lactational period.

Effect of Ruta graveolens and Cannabis sativa alcoholic extract on spermatogenesis in the adult wistar male rats

Objective:

The present study was undertaken to evaluate the effects of alcohol extracts of Ruta graveolens and Cannabis sativa that were used traditionally in medieval Persian medicine as male contraceptive drugs, on spermatogenesis in the adult male rats.

Materials and Methods:

Ethanol extracts of these plants were obtained by the maceration method. The male rats were injected intraperitionaly with C. sativa and R. graveolens 5% ethanol extracts at dose of 20 mg/day for 20 consecutive days, respectively. Twenty-four hours after the last treatment, testicular function was assessed by epididymal sperm count.

Result:

The statistical results showed that the ethanol extracts of these plants reduced the number of sperms significantly (P=0.00) in the treatment groups in comparison to the control group. The results also showed that the group, treated by extract of R. graveolens reduced spermatogenesis more than the group treated by extracts of C. sativa.

Conclusion:

The present study demonstrated the spermatogenesis reducing properties of the ethanol extracts of R. graveolens and C. sativa in the adult male wistar rats but more studies are necessary to reveal the mechanism of action that is involved in spermatogenesis.