Molecular cloning and responsive expression of macrophage expressed gene from small abalone Haliotis diversicolor supertexta

The complete cDNA sequence of macrophage expressed gene (saMpeg1), a perforin-like molecule, was isolated from small abalone (Haliotis diversicolor supertexta) by homology cloning and rapid amplification of cDNA ends (RACE). The full-length cDNA of saMpeg1 was 2781 bp, consisting of a 5'-terminal untranslated region (UTR) of 252 bp, a 3'-terminal UTR of 342 bp with a signal sequence TAA and a poly (A) tail, and an open reading frame of 2184 bp. The deduced protein (saMpeg1) was composed of 728 amino acids, and contains the cytolytic "helix-turn-helix" domain of perforin (residues 171-218), of which the alpha-helices are amphipathic as are those of perforin. A putative single transmembrane domain is located at residues 667-689, and a modified furin cleavage site (KRRRK; residues 689-693) immediately follows. The result of real time quantitative PCR showed that saMpeg1 was highly expressed at 8h and 96 h post-injection of the Gram-negative bacterium Vibrio parahaemolyticus, but there was no change after TBT exposure. The structural similarity to mammalian perforin and the different gene expression level to bacterial infection and TBT exposure suggest that saMpeg1 may play a role in the immune response against microorganisms in small abalone.

An improved barnacle attachment inhibition assay

The Balanus amphitrite attachment inhibition assay, developed by Rittschof et al. (1992), has been widely used for screening antifouling compounds. One shortcoming of this assay, however, is the low (often < 40%) attachment rate of cyprids, including in the controls that contain seawater only. In this study, trapping of cyprids at the air-water interface was found to be a main contributor to the low attachment rate. Procedures to eliminate the air-water interface were thus introduced. With the improved bioassay, a much higher cyprid attachment rate (>70%) was attained. To further illustrate the usefulness of the improved assay (ie eliminating the air-water interface), the effects of the length of cyprid storage and the effect of a reference biocide, tributyltin chloride, on the survival and attachment rate of the cyprids were examined. The length of cyprid storage was important, with newly molted cyprids, 3- to 9-day old cyprids and 12-day old cyprids having an attachment rate of 43%,>75% and 36%, respectively. The low attachment rate in the newly molted cyprids was due to a high percentage of cyprids that still swam at the end of exposure period, whereas the low attachment rate in the 12-day old cyprids was due to a high mortality rate. The cyprids showed an EC50 of 22 microg l(-1) for attachment inhibition and LC50 of 25 microg l(-1) for mortality. It is concluded that the air-water interface has an important confounding effect on cyprid attachment rate in the conventional B. amphitrite attachment assay. By eliminating the air-water interface more robust quantitative assay results were obtained.

Differential effects of tributyltin and copper antifoulants on recruitment of non-indigenous species

Maritime transport is a primary vector for many marine invaders. For the past two decades, most commercial vessels have used tributyltin (TBT) antifouling (AF) paint, whereas recreational vessels have been restricted to alternatives, most commonly containing copper. Settlement plates painted with a collar of copper or TBT AF paint, and unpainted control plates, were deployed in commercial and recreational embayments in Port Jackson, Australia, and sampled photographically after 5 and 10 months. Copper enhanced early recruitment of several non-indigenous species (NIS), whereas recruitment of indigenous species was typically reduced by copper. TBT limited the recruitment of NIS for just 5 months and indigenous species, for the entire study. The results suggest that the use of toxic AF paints, and the possible accumulation of AF biocides in embayments, may be negatively affecting indigenous epibiota. Conversely, copper antifoulants on recreational vessels may be facilitating the transport and establishment of copper tolerant NIS into disturbed estuarine habitats.

Mitochondrial metabolism of 17alpha-hydroxyprogesterone in male sea bass (Dicentrarchus labrax): a potential target for endocrine disruptors

The metabolism of 17alpha-hydroxyprogesterone (17P(4)) was investigated in different subcellular fractions isolated from male gonads of sea bass (Dicentrarchus labrax L). The existence of CYP17 (C17,20-lyase activity) and CYP11B (11beta-hydroxylase) catalyzed reactions was demonstrated in the mitochondrial fraction, where 17P(4) was converted to androstenedione (AD) and further metabolized to 11beta-hydroxyandrostenedione (betaAD). The synthesis of betaAD predominated in early spermatogenic testis, indicating a role of betaAD in testicular recrudescence. Additionally, the in vitro effect of model endocrine disrupting chemicals (i.e. nonylphenol (NP), p,p'-DDE, benzo[a]anthracene (BaA), tributyltin (TBT) and ketoconazole (KCZ)) on the mitochondrial metabolism of 17P(4) was investigated. Among the tested compounds, 100 microM NP inhibited the activity of CYP17 (C17,20-lyase) whereas 100 microM KCZ inhibited both CYP17 and CYP11B. Both chemicals showed the potential to disrupt the reproductive cycle of fish living in polluted environments due to impairment of testicular steroid biosynthesis. These results suggest that mitochondrial metabolism of 17P(4) may constitute a new sensitive probe for the assessment of endocrine disruption in fish.

The effect of tributyltin on human eosinophilic [correction of eosinophylic] leukemia EoL-1 cells

Organotin compounds are chemicals that are widely used in industry and agriculture as plastic stabilizers, catalysts and biocides. Many of them, including tributyltin (TBT), have been detected in human food and, as a consequence, detectable levels have been found in human blood. As organotin compounds were shown to possess immunotoxic activity, we focused our attention on the effect of TBT on the basic determinants of the function of eosinophils, i.e. cell adhesiveness and motility. We used human eosinophylic leukemia EoL-1 cells, a common in vitro cellular model of human eosinophils. Here, we demonstrate that TBT causes a dose-dependent decrease in the viability of EoL-1 cells. When administered at sub-lethal concentrations, TBT significantly decreases the adhesion of EoL-1 cells to human fibroblasts (HSFs) and inhibits their migration on fibroblast surfaces. Since the basic function of eosinophils is to invade inflamed tissues, our results indicate that TBT, and possibly other organotin compounds, may affect major cellular properties involved in the determination of in vivo eosinophil function.

Toxicogenomics and ecotoxicogenomics for studying endocrine disruption and basic biology

Chemicals released into the environment have the potential to disrupt the endocrine system in wild animals, mouse, and humans. To understand molecular mechanisms of chemical toxicity in various species, toxicogenomics/ecotoxicogenomics, describing the integration of genomics (trascriptomics, proteomics and metabolomics) into toxicology/ecotoxicology, needs to be established as a powerful tool for research. Ecotoxicogenomics is defined as the study of gene and protein expression in non-target organisms that is important in responses to environmental toxicant exposures. Estrogen-responsive genes and estrogen response element(s) in genes have been identified in the mouse reproductive tract by application of cDNA microarray technology. Additionally, functional mechanisms of tributyltin action via nuclear receptors such as retinoid X receptor alpha and peroxisome proliferator activated receptor gamma also have been identified using cDNA microarray. A microarray system has been established for Daphnia magna. Toxicogenomics/ecotoxicogenomics provide powerful tools to help us understand not only molecular mechanisms of chemical toxicity but also the basic biology of various animal species.

Cytotoxic effects and aromatase inhibition by xenobiotic endocrine disrupters alone and in combination☆

Xenobiotics may cause long-term adverse effects in humans, especially at the embryonic level, raising questions about their levels of exposure, combined effects, and crucial endpoints. We are interested in the possible interactions between xenobiotic endocrine disrupters, cellular viability and androgen metabolism. Accordingly, we tested aroclor 1254 (A1254), atrazine (AZ), o,p'-DDT, vinclozolin (VZ), p,p'-DDE, bisphenol A (BPA), chlordecone (CD), nonylphenol (NP), tributylin oxide (TBTO), and diethylstilbestrol (DES) for cellular toxicity against human embryonic 293 cells, and activity against cellular aromatase, but also on placental microsomes and on the purified equine enzyme. Cellular viability was affected in 24 h by all the xenobiotics with a threshold at 50 microM (except for TBTO and DES, 10 microM threshold), and aromatase was inhibited at non-toxic doses. In combination synergism was observed reducing the threshold values of toxicity to 4-10 microM, and aromatase activity by 50% in some cases. In placental microsomes the most active xenobiotics rapidly inhibited microsomal aromatase in a manner independent of NADPH metabolism. Prolonged exposures to low doses in cells generally amplified by 50 times aromatase inhibition. These xenobiotics may act by inhibition of the active site or by allosteric effects on the enzyme. Bioaccumulation is a feature of some xenobiotics, especially chlordecone, DDT and DDE, and low level chronic exposures can also affect cell signaling mechanisms. This new information about the mechanism of action of these xenobiotics will assist in improved molecular design with a view to providing safer compounds for use in the (human) environment.

Bis(tributyltin)oxide (TBTO) decreases the food allergic response against peanut and ovalbumin in Brown Norway rats

Other factors than the allergen itself may be of importance in the development of food allergy. This report describes the influence of the immunosuppressive compound bis(tributyltin)oxide (TBTO), present in the food chain, on the development of food allergy to peanut or ovalbumin in Brown Norway (BN) rats. To study these effects BN rats were sensitized to either 1 or 10mg peanut or ovalbumin by daily oral gavage and the TBTO-groups were fed a diet containing 80 mg TBTO per kg diet. Co-exposure to TBTO not only resulted in decreased general immunologic parameters such as weights of mesenteric lymph nodes and Peyer's patches, lymphocyte proliferation rates in splenocytes, but also on allergic parameters. In the peanut allergen-model TBTO decreased allergen-specific Th2 cytokine production by spleen cells, number of eosinophilic and basophilic granulocytes in the blood and production of mast cell protease II after oral food challenge. In the ovalbumin allergen-model TBTO decreased the number of eosinophilic and basophilic granulocytes, allergen-specific IgE and production of mast cell protease II after oral food challenge. The data imply that in the process of risk assessment of food allergy attention should be given to immunomodulating compounds present in the diet.

Effects of tributyltin on the emotional behavior of C57BL/6 mice and the development of atopic dermatitis-like lesions in DS-Nh mice

BACKGROUND

Tributyltin (TBT) compounds have been widely used as antifouling biocides on ships and are known to be endocrine disrupters. However, little is known about the influence of TBT on emotion and atopic dermatitis.

OBJECTIVE

We evaluated the effects of TBT on the emotional behavior of C57BL/6 mice and on development of AD-like skin lesions in DS-Nh mice, which develop dermatitis spontaneously under conventional conditions.

METHODS

Five-week-old C57BL/6 mice were fed 0, 50, 100, 200, 300, 400 or 500 ppm TBT diet for 2 weeks. At the end of the exposure period, an open-field test was performed. Six-week-old DS-Nh mice were fed 200 ppm TBT for 14 weeks. Skin eruption scores were checked every week. Skin biopsy was performed from ears.

RESULTS

No significant difference was found in mortality or body weight among the groups receiving 0-200 ppm TBT diet during the course of the study. In the open-field test, mice fed 200 ppm TBT showed lower activity and higher frequency of defecation than did controls. These figures represent a high level of anxiety and fear and were significant in male mice compared with control mice. The skin eruption score was significantly higher in the DS-Nh mice fed TBT than in control mice. In the DS-Nh mice fed TBT, acanthosis of epidermis and infiltration of inflammatory cells in the dermis were more severe than those in controls.

CONCLUSION

TBT diet induced alterations in emotional behavior in C57BL/6 mice, and also induced early onset and deterioration of AD-like lesions in DS-Nh mice.

Biochemical responses in Salmo salar muscle following exposure to ethynylestradiol and tributyltin

This study investigated the effects of nominal concentrations of two endocrine-disrupting chemicals (EDCs) on fish physiology. The effects of the synthetic pharmaceutical estrogen ethynylestradiol (EE(2)) and the antifoulant tributyltin (TBT) were investigated in exposure studies with immature Atlantic salmon, Salmo salar. Fish were exposed for 7 days to waterborne EE(2), TBT, or a combination of both. The activities of lactate dehydrogenase (LDH), acetylcholinesterase (AchE) and glutathione S-transferase (GST), and lactate and glycogen content were determined in samples of fish muscle. Fish exposed to EE(2) for 3 days responded rapidly with increasing AchE and GST activities and increasing lactate content. These responses were limited to the first 3 days of exposure and had disappeared by day 7, indicating that the fish had adapted to EE(2) exposure. Compared to the controls, TBT increased AchE and LDH activity, inhibited GST activity and had no effect on lactate content. When mixed, the highest concentration of EE(2) increased the effect of TBT on lactate content. However, fish exposed to a lower concentration of EE(2) in combination with TBT had the lowest lactate content. Effects on AchE and LDH activities were smaller when TBT was combined with EE(2) compared to TBT alone. This suggests that TBT and EE(2) influence biochemical processes in fish muscle, acting on different organizational levels, by antagonistic and synergistic mechanisms.

Tributyltin and triphenyltin inhibit osteoclast differentiation through a retinoic acid receptor-dependent signaling pathway

Organotin compounds, such as tributyltin (TBT) and triphenyltin (TPT), have been widely used in agriculture and industry. Although these compounds are known to have many toxic effects, including endocrine-disrupting effects, their effects on bone resorption are unknown. In this study, we investigated the effects of organotin compounds, such as monobutyltin (MBT), dibutyltin (DBT), TBT, and TPT, on osteoclast differentiation using mouse monocytic RAW264.7 cells. MBT and DBT had no effects, whereas TBT and TPT dose-dependently inhibited osteoclast differentiation at concentrations of 3-30 nM. Treatment with a retinoic acid receptor (RAR)-specific antagonist, Ro41-5253, restored the inhibition of osteoclastogenesis by TBT and TPT. TBT and TPT reduced receptor activator of nuclear factor-kappaB ligand (RANKL) induced nuclear factor of activated T cells (NFAT) c1 expression, and the reduction in NFATc1 expression was recovered by Ro41-5253. Our results suggest that TBT and TPT suppress osteoclastogenesis by inhibiting RANKL-induced NFATc1 expression via an RAR-dependent signaling pathway.

Histopathological evidence of antagonistic effects of tributyltin on benzo[a]pyrene toxicity in the Arctic charr (Salvelinus alpinus)

We previously reported that long-term (54 days), repeated intraperitoneal exposure to low doses of tributyltin (TBT; 0.3 mg/kg) inhibited the metabolic activation of co-administered benzo[a]pyrene (BaP; 3 mg/kg) in the Arctic charr (Salvelinus alpinus); BaP, in turn, stimulated the metabolism and/or excretion of TBT. Here, we report the results of histopathological examinations of liver, kidney and pseudobranch tissue samples originating from these same fish. The results revealed higher lesion incidences at all sampling time points (Days 8, 32 and 56) among BaP-exposed fish compared with fish exposed to either TBT alone or combined with BaP. The severity of lesions like necrosis was also higher in BaP-exposed fish. Moreover, hepatic basophilic foci were observed exclusively in fish exposed to BaP alone. Together, these results provide new evidences that TBT can antagonize BaP toxicity in fish exposed to both pollutants under controlled laboratory conditions. In contrast, BaP does not appear to provide protection against TBT toxicity.

Degradation of tributyltin in microcosm using Mekong River sediment

The degradation of tributyltin (TBT) and changes of bacterial number and community structures were investigated in microcosms using the sediment collected from the Mekong River, Vietnam. Concentrations of TBT in sediments were less than 0.62 ng/g (dry wt), lower than those reported from other areas. TBT-resistant bacteria were found in the three sampling sites, and the occurrence rates were 11-16% out of the total viable count. In this microcosm experiment, initial concentration of TBT [1.0-1.4 microg/g (dry wt)] decreased to 0.6 microg/g (dry wt) during 150 days, whereas that in the control microcosm with autoclaved sediment did not change, indicating that Mekong River sediment contains high TBT-degrading activity by microorganisms. The occurrence of TBT-resistant bacteria and the bacterial community structures monitored by denaturing gradient gel electrophoresis were almost the same between test and control groups, indicating that the addition of TBT had little influence on microbial community structure. Mekong River sediment seems to have a stable microbial community against TBT pollution.

Tributyltin-induced cell death is mediated by calpain in PC12 cells

Tributyltin, an endocrine-disrupting chemical, has been used as a heat stabilizer, agricultural pesticide and component of antifouling paints. In this study, we investigated whether calpain is involved in tributyltin toxicity in undifferentiated PC12 cells. Tributyltin (2 microM) induced an increase of lactate dehydrogenase release, a marker of cytotoxicity, in PC12 cells in a time-dependent manner. It also induced calpain activation in a dose-dependent manner, and a calpain inhibitor, MDL28170 (40 microM), decreased the cellular toxicity, suggesting that calpain is involved in tributyltin toxicity in PC12 cells. Because calpain is a calcium-dependent protease, we examined the effect of EGTA, an extracellular Ca(2+) chelator and BAPTA-AM, an intracellular Ca(2+) chelator. Calpain activation induced by tributyltin was decreased by BAPTA-AM (50 microM), but not by EGTA (1 mM), suggesting that calpain activation is associated with calcium release from intracellular Ca(2+) stores. Further, we investigated the relationship between caspase-3 and calpain. Inhibition of caspase-3 reduced calpain activity induced by tributyltin. In conclusion, we have demonstrated that tributyltin induced cell death through calpain activation, and that intracellular Ca(2+) increase and caspase-3 activation are required for calpain activation by tributyltin.

Alteration of an essential NK cell signaling pathway by low doses of tributyltin in human natural killer cells

Tributyltin (TBT), a toxic and widespread environmental contaminant, has been shown to inhibit natural killer (NK) cell cytotoxic function significantly. Inhibition of NK cell cytotoxic function has the potential to increase viral infections and tumor growth. Upon NK cell binding to lysis-sensitive tumor cells, an intracellular pathway is activated, which generally begins with activation of non-receptor protein tyrosine kinases (PTKs) and ends with mitogen-activated protein kinase (MAPK)-mediated release of lytic granules toward the contacted target cell. In the current studies, we used a cytotoxicity assay to examine how low doses (200nM or lower) of TBT affect cytotoxic function. Additionally, we investigated how low doses of TBT modulate the signaling pathway that dictates lytic granule exocytosis. A 1h exposure to 200, 100, 50 and 25nM TBT significantly decreased cytotoxic function 6d later. We also saw significant activation of p38 and p44/42 by as low as 50nM TBT within ten minutes of exposure. The observed activation of MAPKs, p38 and p44/42, implicated their upstream activators MAPK kinases (MAP2Ks). On examining MAP2Ks, MKK3/6 and MEK1/2, activation was seen within ten minutes. However, when the most upstream signaling molecules in this pathway, non-receptor protein tyrosine kinases (PTKs) such as Syk, ZAP-70, Pyk2 and Src were examined, no significant activation was seen. These data imply that upstream activators of MAP2Ks, MAP2K kinases (MAP3Ks), are activated by TBT exposures and/or that MAP2K phosphatases are being inhibited by TBT. Taken together, these data suggest that TBT-induced activation of MAPKs, p38 and p44/42, is caused by their upstream activators MAP2Ks, MKK3/6 and MEK1/2, respectively.

Sexual dimorphism in esterified steroid levels in the gastropod Marisa cornuarietis: the effect of xenoandrogenic compounds

Molluscs can conjugate a variety of steroids to form fatty acid esters. In this work, the freshwater ramshorn snail Marisa cornuarietis was used to investigate sex differences in endogenous levels of esterified steroids. Testosterone and estradiol were mainly found in the esterified form in the digestive gland/gonad complex of M. cornuarietis, and males had higher levels of esterified steroids than females (4-10-fold). Additionally, the ability of several xenobiotics, namely tributyltin (TBT), methyltestosterone (MT) and fenarimol (FEN) to interfere with the esterification of testosterone and estradiol was investigated. All three compounds induced imposex - appearance of male sexual characteristics in females. Exposure to TBT led to a decrease in both esterified testosterone (60-85%) and estradiol (16-53%) in females after 100 days exposure, but had no effect on males. Exposure to FEN and MT did not alter levels of esterified steroids in males or in females, although exposed females developed imposex after 150 days exposure. The decrease in esterified steroids by TBT could not be directly linked with a decrease in microsomal acyl-CoA:testosterone acyltransferase (ATAT) activity, which catalyzes the esterification of steroids. In fact, ATAT activity was marginally induced in organisms exposed to TBT for 50 days (1.3-fold), and significantly induced in males and females exposed to MT for 50 days (1.8- and 1.5-fold, respectively), whereas no effect on ATAT activity was observed after 150 days exposure.

The effect of organotin compounds on gender specific androstenedione metabolism in the freshwater ramshorn snail Marisa cornuarietis

In a recent study, we demonstrated that androstenedione was mainly converted to testosterone (T) and 5alpha-dihydrotestosterone (DHT) by digestive gland/gonad complex microsomal fractions isolated from male Marisa cornuarietis, whereas it was primarily metabolized to 5alpha-dihydroandrostenedione (DHA) by females. In the present work, the sexual dimorphic metabolism of androstenedione was further investigated, and attributed to a higher 17beta-hydroxysteroid dehydrogenase activity in males than in females. Thereafter, the hypothesis was tested that the metabolism of androstenedione might be affected by exposure to tributyltin (TBT) and triphenyltin (TPT), which are known to induce the development of imposex in several gastropod species. The in vitro metabolism of androstenedione, particularly the formation of DHA and DHT, was inhibited by both compounds. However, in vivo experiments showed no significant alteration in the metabolism of androstenedione in males, but a marginal (TBT) and a significant (TPT) inhibition of the formation of DHA in females exposed for 150 days to concentrations that had significantly induced the development of imposex. The ratio DHT+T/DHA, a possible indicator of metabolic androgenization, tended to increase (0.43 versus 0.35, p=0.06) in TPT exposed females. However, this ratio never reached values comparable to those found in males (11+/-1).

Tributyltin inhibits osteoblastic activity and disrupts calcium metabolism through an increase in plasma calcium and calcitonin levels in teleosts

To examine the direct effects of tributyltin acetate (TBTA) on osteoclasts and osteoblasts, teleost scale, which has both osteoclasts and osteoblasts and is similar to mammalian membrane bone, was used in the present study. The activities of tartrate-resistant acid phosphatase and alkaline-phosphatase, as respective indicators of activity in both cells, were used. In freshwater teleost (goldfish) and marine teleosts (nibbler and wrasse), the osteoclastic activity in the scales did not change as a result of TBTA treatment (10(-9) to 10(-5) M). However, the osteoblastic activity decreased in the goldfish, nibbler, and wrasse after 6 h of incubation. In goldfish, even 10(-10) M of TBTA significantly inhibited the osteoblastic activity. The inhibitory activity in goldfish was stronger than that in nibbler and wrasse. Therefore, details of the mechanism were examined using goldfish. The mRNA expressions of the estrogen receptor and insulin-like growth factor-I, which participate in osteoblastic growth and differentiation, decreased in the TBTA-treated scales. However, the mRNA expression of metallothionein (MT), a metal-binding protein that protects the organism from heavy metal, increased much less than those of cadmium and methyl-mercury. Furthermore, we showed that the plasma calcium and hypocalcemic hormone (calcitonin) level increased in goldfish kept in water containing TBTA (10(-10) and 10(-8) M). The current data are the first to demonstrate that, in teleosts, TBTA inhibits osteoblastic activity without affecting osteoclastic activity and disrupts the calcium metabolism, including the calcemic hormone, in goldfish.

5,6-Dichloro-1-methylgramine, a non-toxic antifoulant derived from a marine natural product

The laboratory culture of the barnacle, Balanus amphitrite has made it possible to supply cypris larvae for antifouling assays all year round. The settlement of cyprids obtained from cultured B. amphitrite was indistinguishable from cyprids reared from field-collected barnacles. In laboratory cyprid settlement assays of extracts from marine sessile organisms, antifouling activity was expressed as the 99% inhibitory concentration (IC99), and toxicity as the 30% lethal concentration (LC30). The lipophilic extract of the marine bryozoan, Zoobotryon pellucidum, which showed promising antifouling activity, yielded 2,5,6-tribromo-1-methylgramine (TBG) by bioassay-guided isolation. The inhibitory activity of TBG was 6 times as strong as that of bis-(n-butyltin)oxide (TBTO), while its toxicity to cypris larvae was one-tenth that of TBTO. A structure-activity relationship study with 155 indole derivatives led to the discovery of the non-toxic antifoulant candidates 5,6-dichlorogramine, 5-chloro-2-methylgramine, and 5,6-dichrolo-1-methylgramine (DCMG), the latter being selected as the antifouling paint ingredient for performance evaluation tests (panel tests) following the results of a preliminary safety tests. A silicone-based antifouling paint containing 5-10% of DCMG was prepared and tested in the field; the painted surfaces remained almost barnacle-free for 1.5 years similar to silicone coatings such as Biox. Since the leaching rate of DCMG from the paint surface could be controlled by the addition of an acrylic acid-styrene copolymer (ASP), the life of the antifouling performance is expected to be improved. Thus, an extremely non-toxic silicone-based antifouling paint containing DCMG is under development.

Study of neonatal exposure to androgenic endocrine disruptors, testosterone and dihydrotestosterone by normal-phase HPLC

Neonatal exposure to androgen induces developmental abnormalities in the male reproductive system. To investigate whether neonatal exposure affects spermatogenesis in juvenile and pubertal testis, Sprague-Dawley rat pups were given androgen or various androgenic endocrine disruptors by a single injection on the day of birth at concentrations ranging between 4 mm to 200 mm, and sacrificed on day 21 (juvenile) or 50 (puberty). The testes were weighed and examined histologically at each stage. Further, the metabolites of steroidogenesis were analyzed using normal-phase high-performance liquid chromatography. Neonatal exposure significantly reduced testis weights and steroidogenesis of juveniles. Neonatal exposure to testosterone and dihydrotestosterone still suppressed pubertal steroidogenesis, although testis weight was completely restored during puberty.

Tributyltin disturbs bovine adrenal steroidogenesis by two modes of action

Tributyltin, an environmental pollutant, affected adrenal steroid hormone biosynthesis by two modes of action. Treatment of bovine adrenal cultured cells with 10-100 nM tributyltin for 48 h suppressed cortisol and androstenedione secretion, but induced the accumulation of 17alpha-hydroxyprogesterone and deoxycortisol, indicating that the P450(C21) and P450(11beta) activities were specifically suppressed. Direct inhibition of the enzymatic activities due to tributyltin was not observed in isolated organelles of untreated cells at concentrations less than 10 microM. Western blotting experiments using specific antibodies against steroidogenic enzymes showed that treatment with 1-100 nM tributyltin caused a decrease in cellular P450(C21) and P450(11beta) protein levels, and real-time PCR experiments showed that the decrease in protein content was attributable to decreases in mRNA of the enzymes. Tributyltin at concentrations higher than 100 nM suppressed all steroid biosynthesis in the adrenal cells. This suppression was closely correlated to the decrease in steroidogenic acute regulatory protein. Since nanomolar concentrations of tributyltin disturbed steroidogenesis in mammalian cells, there is the possibility that steroid hormone synthesis in polluted wild animals is affected by this compound.

Effect of triorganotin compounds on membrane permeability

Organotin compounds are widely distributed toxicants. They are membrane-active molecules with broad biological toxicity. In this contribution, we study the effect of triorganotin compounds on membrane permeability using phospholipid model membranes and human erythrocytes. Tribultyltin and triphenyltin are able to induce the release of entrapped carboxyfluorescein from large unilamellar vesicles. The rate of release is similar for phosphatidylcholine and phosphatidylserine systems and the presence of equimolar cholesterol decreases the rate of the process. Release of carboxyfluorescein is almost abolished when a non-diffusible anion like gluconate is present in the external medium, and it is restored by addition of chloride. Tributyltin is able to cause hemolysis of human erythrocytes in a dose-dependent manner. Relative kinetics determination shows that potassium leakage occurs simultaneously with hemoglobin release. Hemolysis is reduced when erythrocytes are suspended in a gluconate medium. These results indicate that triorganotin compounds are able to transport organic anions like carboxyfluorescein across phospholipids bilayers by exchange diffusion with chloride and suggest that anion exchange through erythrocyte membrane could be related to the process of hemolysis.

Species-Specific Isotope Dilution Analysis and Isotope Pattern Deconvolution for Butyltin Compounds Metabolism Investigations

A methodology for the study of the absorption and metabolism of butyltin compounds in laboratory animals using isotopically enriched species was developed. The method is based on the oral administration of 119Sn-labeled monobutyltin (MBT), 118Sn-labeled dibutyltin (DBT), and 117Sn-labeled tributyltin (TBT) to the animals and the measurement of both the concentration and isotopic composition of these compounds in the different tissues by GC-ICPMS. The degradation of butyltin compounds during their metabolism was computed using least-squares isotope pattern deconvolution, and their concentration was measured by reverse isotope dilution analysis using natural-abundance MBT, DBT, and TBT standards. Male Wistar rats were used as models to evaluate the proposed methodology. Preliminary toxicological results obtained with one rat indicate that TBT is highly absorbed (64.4%), and it is found in all organs with relatively high levels in stomach and intestines. The apparent absorption of DBT was 27.3% and was mainly found in liver, kidney, and intestines. However, a large proportion of the found DBT is formed from the degradation of TBT (approximately 40% of the found DBT in liver is degraded TBT). The apparent absorption of MBT was found to be 12.5%, and the originally administered MBT was mainly recovered in the feces. However, MBT was clearly detected in liver, kidney, stomach, intestines, and urine as degradation products of DBT and TBT. Although a significant variability from rat to rat is expected to be obtained, the analytical variability provided by this methodology is small enough to yield meaningful biological results. The results obtained demonstrate that the developed methodology is able to follow qualitatively, quantitatively, and simultaneously the specific metabolic pathways of different species of a given element.

Comparative study of tributyltin toxicity on two bacteria of the genus Bacillus

Tributyltin is a potent biocide mainly used in marine anti-fouling paints. Owing to its widespread distribution in coast areas and its high toxicity to aquatic organisms, the use of this compound is generally restricted and under government regulation. Despite of that, it persists in the aquatic environment. Organotins used in industry have also been detected in terrestrial environments. The persistence and high lipophilicity explain bioaccumulation. The role of bacteria in recycling organic matter prompted us to study the interaction of tributyltin with two ubiquitous bacilli, B. stearothermophilus and B. subtilis, proposed as biological indicators of pollutants with ecological impact. These bacteria have been used as suitable models for the study of toxicity mechanisms of unselective lipophilic compounds (e.g., DDT and endosulfan). Drug effects on growth parameters, oxygen consumption and membrane organization were assessed. Bacteria growth in a liquid complex medium was disturbed by concentrations of TBT as low as 25 nM (8 microgL(-1)), close to the concentration in polluted environments. The respiratory activity is affected by TBT in both microorganisms. Membrane organization, assessed by fluorescence polarization of two fluidity probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and a propionic acid derivative (DPH-PA), was also perturbed by the xenobiotic. Alterations on growth, oxygen consumption and physical properties of membrane lipids are stronger in B. stearothermophilus as compared to B. subtilis. A putative relationship between growth inhibition and respiratory activity impairment induced by TBT and its effects on the physical behaviour of bacterial membrane lipids is suggested.

Triphenyltin and Tributyltin inhibit pig testicular 17beta-hydroxysteroid dehydrogenase activity and suppress testicular testosterone biosynthesis

We previously reported that tributyltin chloride (TBT) and triphenyltin chloride (TPT) powerfully suppressed human chorionic gonadotropin- and 8-bromo-cAMP-stimulated testosterone production in pig Leydig cells at concentrations that were not cytotoxic [Nakajima Y, Sato Q, Ohno S, Nakajin S. Organotin compounds suppress testosterone production in Leydig cells from neonatal pig testes. J Health Sci 2003;49:514-9]. This study investigated the effects of these organotin compounds on the activity of enzymes involved in testosterone biosynthesis in pig testis. At relatively low concentrations of TPT, 17beta-hydroxysteroid dehydrogenase (17beta-HSD; IC(50)=2.6microM) and cytochrome P450 17alpha-hydroxylase/C(17-20) lyase (IC(50)=117microM) activities were inhibited, whereas cholesterol side-chain cleavage cytochrome P450 and 3beta-HSD/Delta(4)-Delta(5) isomerase activities were less sensitive. Overall, TPT was more effective than TBT. TPT also inhibited both ferredoxin reductase and P450 reductase activities at concentrations over 30microM; however, TBT had no effect, even at 100microM. The IC(50) values of TPT were estimated to be 25.7 and 22.8microM for ferredoxin reductase and P450 reductase, respectively. The inhibitory effect of TPT (30microM) on microsomal 17beta-HSD activity from pig testis was eliminated by pretreatment with the reducing agents dithiothreitol (1mM) and dithioerythritol (1mM). On the other hand, TPT (0.03microM) or TBT (0.1microM) exposure suppressed the testosterone production from androstenedione in pig Leydig cells indicating that these organotins inhibit 17beta-HSD activity in vivo as well as in vitro, and the IC(50) values of TPT and TBT for 17beta-HSD activity were estimated to be 48 and 114nM, respectively. Based on these results, it appears possible that the effects of TBT and TPT are largely due to direct inhibition of 17beta-HSD activity in vivo.