[pt] O objetivo, deste trabalho, foi avaliar as concentrações de mercúrio total (HgT) e metilmercúrio (MeHg) bem como a % MeHg no tecido muscular, no fígado e na gônada da corvina (Micropogonias furnieri; carnívora), do bagre (Bagre spp.; onívoro) e da tainha (Mugil liza; planctívora). Além de alguns parâmetros bióticos tais como: comprimento, peso, idade, maturidade sexual e o sexo. Foi possível estabelecer uma comparação entre as concentrações de HgT no tecido muscular da corvina e da tainha ao longo dos últimos treze anos. A concentração de HgT foi determinado através de EAA - vapor frio utilizando borohidreto de sódio como agente redutor. E a concentração MeHg foi determinada através de GC-DCE. Para o controle de qualidade analítica utilizaram-se amostras de padrões certificados IAEA MA-1 e Dolt-2. As concentrações de HgT e MeHg no tecido muscular dos carnívoros foram maiores que nos onívoros seguidos pelos planctívoros. O fígado de todas as espécies apresentaram as maiores concentrações de HgT. Enquanto, no músculo as maiores concentrações observadas foram de MeHg. A corvina apresentou a maior percentagem de MeHg no fígado comparada ao bagre e a tainha. Nas gônadas a % MeHg correspondeu a 100 %. Foi observada uma correlação significativa e positiva entre a concentração de HgT no tecido muscular do bagre e seu comprimento e peso. Utilizando-se o teste de Mann-Whitney foi observada uma diferença significativa entre as concentrações de HgT e o estágio de vida dos indivíduos, tanto para a corvina como para a tainha. Os resultados apresentaram uma diferença estatisticamente significativa entre as concentrações de HgT no músculo tanto das corvinas quanto das tainhas coletadas nos anos de 1999 e 2003. / [en] This study assesses the concentration of total mercury (THg), methylmercury (MeHg) and the % MeHg in muscle tissue, liver and gonad of three fish species (Micropogonias furnieri - Atlantic croaker; carnivorous fish, Bagre spp. - Catfish; omnivorous fish and Mugil liza - mullet; planktivorous fish). Furthermore, some other biotic parameters with: total length, weight, age, sexual maturity and sex. The mercury concentration along the last thirteen years in Atlantic croaker and mullet muscle tissue was assessed. THg concentrations were determined by cold vapour AAS with sodium borohydride as a reducing agent. The MeHg was made by CG-ECD. Theses analytical methodologies presented high precision and accuracy when tested with certified reference materials from IAEA - MA-1 and DOLT 2. The carnivorous fish showed higher THg and MeHg concentrations in its muscles than omnivorous and planktivorous fish. The liver of all fish species showed higher THg concentrations than the muscle tissues and gonad. Meanwhile, the MeHg concentrations were higher in the muscle. Atlantic croaker presented higher percentage of MeHg in liver than catfish and mullet. The fish species showed similar percentage of MeHg in their gonad. Significant and positive correlations were observed between THg concentration in catfish muscle and their total length and weight. Mann-Whitney test showed that the stage of the life of the individuals was one of the parameters that influenced THg concentration in the muscle for carnivorous fish planktivorous fish. The results presented a statistically significant difference between the THg in the muscle of the organisms of the Atlantic croaker and the mullet collected in the years 1999 and 2003.

Les Bactéries sulfato-réductrices (BSR) représentent un groupe fonctionnel majeur dans les habitats aquatiques en intervenant dans les processus de minéralisation de la matière organique. En plus de leur implication dans le cycle du carbone et du soufre, les BSR sont considérées comme les principaux producteurs de méthylmercure en milieu côtier, un composé neurotoxique extrêmement bioaccumulable dans les réseaux trophiques. Dans ce contexte, la diversité des BSR dans les sédiments et le panache de l'estuaire de l’Adour (France) a été évaluée par une approche polyphasique incluant le clonage des gènes dsrAB et une méthode de culture haut-débit en microplaques 384 puits. Ces deux techniques ont fourni des données très complémentaires et donc, une meilleure représentation de la diversité sulfato-réductrice réellement présente dans l’estuaire. La réduction des volumes de culture à raison de 100 µL a permis d’améliorer significativement l’efficacité d’isolement des BSR. Près de 200 souches ont été isolées et identifiées à partir des sédiments et du panache de l’estuaire, et plusieurs d'entre elles ont constitué de nouveaux taxons cultivés. En parallèle, un biosenseur luminescent sensible spécifiquement au méthylmercure a été appliqué pour l’étude de la méthylation du mercure par les BSR. Cet outil simple et rapide constitue une bonne alternative aux méthodes de détection chimique traditionnellement utilisées pour évaluer les potentiels de méthylation du mercure des micro-organismes. L’analyse de la production de méthylmercure chez 21 BSR affiliées à la famille des Desulfobulbaceae a permis d’identifier des souches méthylantes, dont certaines ont été identifiées comme abondantes dans les sédiments de l’estuaire. À long terme, l’utilisation du biosenseur pour l’analyse des capacités de méthylation du mercure chez les BSR ou d’autres groupes fonctionnels permettra de mieux connaître la distribution phylogénétique des micro-organismes méthylants et d'appréhender le déterminisme génétique de ces transformations. / Sulfate-Reducing Bacteria (SRB) represent a significant part of the standing microbial communities living in coastal sediments. This functional group is involved in the decomposition and the mineralization of organic matter as well as in the sulfur cycle. In addition, production of methylmercury was shown to be mainly driven by SRB in aquatic ecosystems. Environmental methylation of inorganic mercury constitutes a human health issue due to its neurotoxic effect and its biomagnification in aquatic food webs. In this context, sulfate-reducing diversity was evaluated in anoxic sediments, as well as in the water plume of the Adour estuary. SRB were characterized through a polyphasic approach including dsrAB genes analysis and high throughput isolations in 384-well microplates. As a result, the microplate approach contributed to assess a significant part of the sulfate-reducing community and provided complementary results to the molecular approach. High-throughput SRB isolation permitted a rapid access to numerous but also original strains and around 200 SRB were isolated and identified from the estuarine sediments and the estuarine plume. Beside, the mercury methylation potentials of 21 sulfate reducing strains were determined using a bacterial sensor. All strains were related to the Desulfobulbaceae family and the capacity to produce methylmercury varied a lot. This work permit to identify some methylating strains identified as abundant in the Adour estuarine sediments. On the long view, the use of the biosensor to assess the mercury methylation potential will offer a better knowledge on the distribution of methylating bacteria among the SRB and other functional groups and could help to identify the molecular determinism beside these transformations.

Os efeitos tóxicos decorrente do consumo de peixes contaminados com metilmercúrio (MeHg) tem sido muito discutido no Brasil, especialmente na Região Amazônica, onde estudos a esse respeito têm mostrado resultados conflitantes. Fatores nutricionais associados à exposição ao MeHg ou a forma na qual o MeHg se encontra ligada no peixe poderiam estar alterando sua toxicidade. Diante destas controvérsias, ratos foram subcronicamente expostos à solução de MeHg, selênio (Se) e óleo de peixe, ou foram alimentados com ração contendo peixes contaminados com MeHg. Biomarcadores de estresse oxidativo, presença de processo inflamatório, genotoxicidade, pressão sistólica, concentração de óxido nítrico (NO), de mercúrio (Hg) total e de Se em diferentes tecidos foram avaliados. Ratos expostos à solução de MeHg, mostraram significante diminuição de antioxidantes endógenos, aumento na peroxidação lipídica, hipertensão, inflamação de tecidos, dano ao DNA e diminuição de NO. A associação MeHg+Se mostrou significativa proteção antioxidante e antigenotóxica, porém não foi capaz de proteger a inflamação induzida pelo MeHg e, surpreendentemente, ratos tratados somente com Se apresentaram aumento significativo na pressão sistólica. Na associação MeHg+óleo de peixe observou-se significativa ação anti-inflamatória, antigenotóxica e anti-hipertensiva, porém não se observou ação antioxidante do óleo de peixe. A absorção do Hg nos diferentes tecidos não foi modificada pela presença de Se ou óleo de peixe. Já em ratos que receberam ração contendo peixe contaminado com MeHg, poucas alterações foram observadas. Houve aumento do biomarcador de peroxidação lipídica malondialdeído em ratos que receberam a ração com o peixe contaminado, bem como a indução de dano no DNA. A partir da 11ª semana, hipertensão também foi observada e o NO não se alterou. Assim, observou-se que o MeHg em solução induziu efeitos oxidantes, inflamação, genotoxicidade e hipertensão, e o MeHg presente no peixe induziu efeitos consideráveis, porém menos severos. A forma química com que o MeHg está presente no peixe, combinado com os nutrientes do peixe como o Se e os ácidos graxos poliinsaturados poderiam estar contribuindo para reduzir os efeitos tóxicos desse elemento. / The toxic effects due the consumption of fish contaminated with methylmercury (MeHg) have been widely discussed in Brazil, especially in Amazon region, where studies have shown confound results. Nutritional factors associated with MeHg exposure or the form of MeHg in fish could be changing MeHg toxicity. Thus, rats were subchronically exposed to MeHg in solution, selenium (Se) and fish oil, or rats were fed with a diet containing MeHg-contaminated fish. Oxidative stress biomarkers, presence of inflammation, genotoxicity, systolic blood pressure, nitric oxide (NO) levels and total mercury (Hg) and Se in different tissues were determined. Rats exposed to MeHg in solution showed endogenous antioxidants significantly reduced, increase of lipid peroxidation, hypertension, tissue inflammation, DNA damage and decrease of NO levels. MeHg+Se association presented antioxidant protection and antigenotoxic effetc, but it was not able to protect the inflammation induced by MeHg. Surprisingly, rats treated only with Se also showed increase in systolic blood pressure. MeHg+fish oil association presented a significant antiinflammatory and antigenotoxic effects and antihypertensive action; however it was not observed antioxidant capacity of fish oil. Hg absorption in different tissues was not modified by Se or fish oil treatments. On the other hand, rats fed with diet containing MeHg-contaminated fish presented few alterations in biomarkers. A lipid peroxidation biomarker showed significantly increased in rats fed with MeHgcontaminated fish as well as induction of DNA damage. From the 11th week, a hypertension was observed and NO levels did not change. In conclusion, it was observed that MeHg solution was able to induce oxidative effects, inflammation, genotoxicity and hypertension, and MeHg linked in fish induced considerable but mild effects. The chemical form that MeHg is present in fish combined with nutrients from fish, as Se and polyunsaturated fatty acids could contribute to reducing toxic effects of MeHg.

The thesis examines aspects of the construction of methylmercury as an authoritative object of knowledge for Chisasibi, a Cree community on the James Bay coast in northern Quebec. I describe the evolution of a particular set of spheres of exchange which mediate economic relations between the Cree communities, the governments of Quebec and Canada, and state and corporate structures tied to the state. Knowledge claims about mercury can be seen as situated among claims of injury in a moral economy which is based on conflict over the James Bay hydro-electric project. The politicization and subsequent medicalization of these knowledge claims are described. Finally, I trace the emergence of particular concepts of 'normality', 'risk' and 'risk group' in medical and technocratic discourses about the effects of methylmercury on Canadian aboriginal populations.

Mercury (Hg) is a toxicant of global concern, but few strategies exist to evaluate its biological effects on the ecosystem. Piscivorous wildlife, such as mink (Mustela vison), are particularly at risk because they can bioaccumulate Hg to concentrations known to impair neurological systems. Given that biochemical changes in the brain precede functional and structural impairments, I evaluated the use of neurochemicals as early-warning biomarkers of Hg toxicity in mink. Initial studies demonstrated that neurochemical biomarkers could be measured from mink carcasses collected from the field, as long as factors such as storage temperature and freeze thaw cycles were accounted for. To determine if Hg could directly impair neurochemicals in mink, an in vitro study demonstrated that Hg (HgCl2 and MeHg) could inhibit radioligand binding to the muscarinic cholinergic (mACh) receptor in the cerebellum and cerebral cortex regions of the brain. By analyzing whole brains collected from wild mink, it was demonstrated that a significant positive correlation existed between concentrations of brain Hg and levels of mACh receptors. These field observations were confirmed by results from a controlled methyl Hg (MeHg) feeding trial in captive mink, whereby sub-chronic exposure of mink to 0.5 - 2 ppm MeHg (ecologically relevant levels) resulted in significant increases in acetylcholinesterase activity and mACh receptor levels in specific brain regions. Collectively, these results demonstrated that exposure of mink to environmentally realistic concentrations of Hg can be related to alterations in neurochemicals at multiple tiers of biological organization. Given the importance of a functional nervous system in wildlife health, the physiological and ecological significance of these findings need further exploration. The results demonstrate that neurochemical approaches may be novel biomarkers to assess the ecotoxicology of Hg, and by extension, other pollutants o

Decomposition and MeHg concentration were measured for Sphagnum fuscum, Sphagnum angustifolium and Chamaedaphne calyculata in a poor fen in the low boreal forest zone of the Canadian Shield. Litter bags were transplanted reciprocally into hummocks, hollows and lawns and retrieved after 1, 2, 3,11 and 15 months. / Mass losses follow the trend: Chamaedaphne calyculata >> S. angustifolium > S. fuscum. Between species differences were far more significant than differences between locations or depths, indicating that litter quality is the major control on decomposition. / McHg concentrations generally increased during decomposition, particularly near the water table: for C. calyculata up to 13000%, for the two Sphagnum mosses up to 500%, suggesting that decomposition stimulates mercury methylation or McHg scavenging. / The discovery of a high McHg substance on C. calyculata leaf surfaces (25 ng g-1) suggests that much plant MeHg data may by skewed by the presence of a biologically active 'film'.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this work, different sample preparation procedures for determining inorganic (in Hg2+ form) and organic mercury (in methylmercury form CH3Hg+) in edible mushrooms were evaluated. Conventional, microwave (MW) and ultrasound (US) assisted extractions combined with water, hydrochloric acid and L-cysteine solutions were tested. Liquid chromatography-chemical vapor generation-inductively coupled plasma mass spectrometry (LC-CVG-ICP-MS) was used for Hg species determination. Total Hg was determined by CVG-ICP-MS after sample decomposition. The influence of the main parameters on Hg species extraction, such as extraction solutions concentration, temperature, US amplitude and extraction time were investigated. Hg species conversion was observed in all conditions when HCl was used as extractor medium. Besides, Hg species extraction from the samples is not quantitative. No Hg species conversion was observed when water and 1.0% (m/v) L-cysteine solution were used. However, the extractions were not quantitative when water was used. Quantitative extractions were obtained only when 1.0% (m/v) L-cysteine was used as extraction solution for conventional and US assisted extractions. The optimized conditions for these procedures (US 20% for 1 min and conventional extraction for 12 h at 25 °C) provided extraction efficiencies higher than 86% for the sum of the Hg species, while only up to 88% of the Hg species were extracted when MW heating was used. The relative standard deviation (RSD) is lower than 8.0 and 13% for Hg2+ and CH3Hg+, respectively. Detection limits for US, MW and conventional extractions (using L-cysteine) were 0.41 and 0.35 ng g-1, 0.64 and 0.90 ng g-1, and 1.41 and 0.11 ng g-1 for Hg2+ and CH3Hg+, respectively. The procedures were evaluated using analyte recovery tests of Hg species and by analysis of certified reference material (DOLT-3). Recoveries in the range of 89 to 109% for Hg2+ and 96 to 113% for CH3Hg+ were obtained. The agreement of the obtained results for DOLT-3 were in the range of 88 to 93% for CH3Hg+ and 95 to 102% for total Hg, respectively. US assisted extraction was considered simpler and faster than the other procedures, being more suitable for Hg species extraction from edible mushrooms. / Neste trabalho foram avaliados diferentes procedimentos de preparo de amostra de cogumelo comestível para a determinação de espécies de mercúrio inorgânico (na forma de Hg2+) e orgânico (na forma de metilmercúrio - CH3Hg+). Para isso, foram avaliadas a extração convencional, a radiação micro-ondas (MW) e o ultrassom (US), combinados com diversos meios extratores (água, soluções de ácido clorídrico e L-cisteína). A cromatografia a líquido com geração de vapor químico acoplado a espectrometria de massa com plasma indutivamente acoplado (LC-CVG-ICP-MS) foi usada para a determinação das espécies de Hg. O Hg total foi determinado por CVG-ICP-MS. A influência dos principais parâmetros envolvidos na extração das espécies de Hg, como a concentração das soluções extratoras, a temperatura na extração por MW, a amplitude de US e o tempo de extração foram investigados. A conversão das espécies de Hg foi observada em todas as condições, quando o HCl foi usado como meio extrator, além de que essas soluções não possibilitaram extrair quantitativamente o Hg das amostras. Entretanto, não foi observada conversão das espécies de Hg em água e na solução de L-cisteína 1,0% (m/v), porém as extrações não foram quantitativas quando a água foi usada como meio extrator. Extrações quantitativas foram obtidas quando L-cisteína 1,0% (m/v) foi usada para os procedimentos de extração convencional e assistida por US. As condições otimizadas para esses procedimentos (US 20% por 1 min e extração convencional por 12 h a 25 °C) proporcionaram efici ências de extração superiores a 86% para a soma das espécies de Hg, com desvio padrão relativo (RSD) menor que 8,0 e 13% para Hg2+ e CH3Hg+, respectivamente. Por outro lado, as extrações assistidas por MW não tiveram eficiências de extração satisfatórias, uma vez que a eficiência máxima obtida foi de 88% para a soma das espécies de Hg. Os limites de detecção obtidos para os procedimentos empregando US, MW e extração convencional foram 0,41 e 0,35 ng g-1, 0,64 e 0,90 ng g-1, e 1,41 e 0,11 ng g-1, para Hg2+ e CH3Hg+, respectivamente. Os procedimentos de extração foram avaliados através de ensaios de recuperação das espécies de Hg, sendo que os mesmos ficaram na faixa de 89 a 109% para Hg2+ e 96 a 113% para CH3Hg+. A exatidão foi avaliada pela análise de material de referência certificado (DOLT-3), cuja concordância dos resultados obtidos em relação aos valores certificados ficou na faixa de 88 a 93% para CH3Hg+ e 95 a 102% para Hg total, respectivamente. A extração assistida por US foi considerada mais simples e rápida que os demais procedimentos, sendo, portanto, mais adequada para a extração das espécies de Hg em cogumelos comestíveis.

Submitted by Alisson Mota (alisson.davidbeckam@gmail.com) on 2015-07-17T18:25:11Z No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:02:10Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:02:12Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:00:05Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-07-17T19:08:17Z (GMT) No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) / Made available in DSpace on 2015-07-17T19:08:17Z (GMT). No. of bitstreams: 1 Dissertação - Maria Cristina Nery do Nacimento Recktenvald.pdf: 2570958 bytes, checksum: c1b8de89a50d2b9065ff5cf49a1e77e3 (MD5) Previous issue date: 2014-09-02 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / To check the influence of the flood pulse of the Solimões River in the Lake Paru (Manacapuru, Amazonas) in this study were determined concentrations of total mercury (THg) and methylmercury (MeHg) in bottom sediments in two seasons. The samples were collected in April (flood) and October (dry) in 2013 at Solimões River Basin. The locations of collected were 10 points; four located under influence of the black waters of the stream that flow into the lake and others next to the Solimões River. To analyze HgT, the sediments samples < 200 mesh were extracted with HCl:HNO3 and filtered through a cellulose membrane (3,0 μm and 9 cm) by approximately two hours. To analyze MeHg the samples < 200 mesh and lyophilized were extracted with 25% KOH/MeOH at 68°C by approximately four hours. The concentrations of HgT were determinates by atomic absorption spectrometry coupled to cold vapor generator (CV-AAS) and MeHg by aqueous ethylation separated by chromatography and detection by atomic fluorescence gas (GC- AFS). The results indicated that the means concentrations of HgT were 89,19 μg kg -1 (flood) and 115,07 μg kg -1 (dry), while the MeHg were 0,78 μg kg -1 (flood) and 0,17 μg kg -1 (dry). In terms of distribution was observed that HgT and MeHg don´t occur in the same way in both periods studied. At dry predominantes the deposition and at flood the remobilization of HgT. The MeHg has increase in the flood. Finally the HgT and MeHg concentrations at bottom sediments show the seasonally effect under the flood pulse at Solimões River and consequently in mercury cycle at the Paru Lake. / A fim de verificar a influência do pulso de inundação do rio Solimões no lago Paru (Manacapuru, Amazonas), neste trabalho foram determinadas as concentrações de mercúrio total (HgT) e metilmercúrio (MeHg) nos sedimentos de fundo em dois períodos do ano. As amostras foram coletas em abril e outubro, correspondendo respectivamente ao período da enchente e ao período da vazante, do ano de 2013, na bacia do rio Solimões. Os locais de amostragens consistiram em dez pontos; quatro localizados sob influência das águas pretas dos igarapés que deságuam no lago e os demais em água branca, próximos ao rio Solimões. Para analisar o HgT, as amostras de sedimentos < 200 mesh foram extraídas com HCl:HNO3 e filtradas em membrana de celulose (3,0 μm e 9 cm) por aproximadamente duas horas. Para analisar o MeHg, as amostras < 200 mesh e liofilizadas foram extraídas com 25% KOH/MeOH a 68°C, por aproximadamente quatro horas. As concentrações de HgT foram determinadas por espectrometria de absorção atômica acoplada ao gerador de vapor frio (CV-AAS) e a de MeHg por etilação aquosa, separada por cromatografia gasosa e detecção por espectrometria de fluorescência atômica (CG-AFS). Os resultados indicaram a concentração média de HgT de 89,19 μg kg -1 (enchente) e de 115,07 μg kg -1, (vazante), enquanto o MeHg foi de 0,78 μg kg -1, (enchente) e de 0,17 μg kg -1, (vazante). Em termos de distribuição observou-se que o HgT e o MeHg não ocorrem da mesma forma nos períodos estudados. Na vazante predomina a deposição e na enchente a remobilização de HgT. Por outro lado, o MeHg tem maior incremento na enchente. Finalmente, as concentrações de HgT e a MeHg nos sedimentos de fundo mostram o efeito da sazonalidade sobre o pulso de inundação do rio Solimões, e consequentemente do ciclo do mercúrio no lago Paru.

Os efeitos tóxicos decorrente do consumo de peixes contaminados com metilmercúrio (MeHg) tem sido muito discutido no Brasil, especialmente na Região Amazônica, onde estudos a esse respeito têm mostrado resultados conflitantes. Fatores nutricionais associados à exposição ao MeHg ou a forma na qual o MeHg se encontra ligada no peixe poderiam estar alterando sua toxicidade. Diante destas controvérsias, ratos foram subcronicamente expostos à solução de MeHg, selênio (Se) e óleo de peixe, ou foram alimentados com ração contendo peixes contaminados com MeHg. Biomarcadores de estresse oxidativo, presença de processo inflamatório, genotoxicidade, pressão sistólica, concentração de óxido nítrico (NO), de mercúrio (Hg) total e de Se em diferentes tecidos foram avaliados. Ratos expostos à solução de MeHg, mostraram significante diminuição de antioxidantes endógenos, aumento na peroxidação lipídica, hipertensão, inflamação de tecidos, dano ao DNA e diminuição de NO. A associação MeHg+Se mostrou significativa proteção antioxidante e antigenotóxica, porém não foi capaz de proteger a inflamação induzida pelo MeHg e, surpreendentemente, ratos tratados somente com Se apresentaram aumento significativo na pressão sistólica. Na associação MeHg+óleo de peixe observou-se significativa ação anti-inflamatória, antigenotóxica e anti-hipertensiva, porém não se observou ação antioxidante do óleo de peixe. A absorção do Hg nos diferentes tecidos não foi modificada pela presença de Se ou óleo de peixe. Já em ratos que receberam ração contendo peixe contaminado com MeHg, poucas alterações foram observadas. Houve aumento do biomarcador de peroxidação lipídica malondialdeído em ratos que receberam a ração com o peixe contaminado, bem como a indução de dano no DNA. A partir da 11ª semana, hipertensão também foi observada e o NO não se alterou. Assim, observou-se que o MeHg em solução induziu efeitos oxidantes, inflamação, genotoxicidade e hipertensão, e o MeHg presente no peixe induziu efeitos consideráveis, porém menos severos. A forma química com que o MeHg está presente no peixe, combinado com os nutrientes do peixe como o Se e os ácidos graxos poliinsaturados poderiam estar contribuindo para reduzir os efeitos tóxicos desse elemento. / The toxic effects due the consumption of fish contaminated with methylmercury (MeHg) have been widely discussed in Brazil, especially in Amazon region, where studies have shown confound results. Nutritional factors associated with MeHg exposure or the form of MeHg in fish could be changing MeHg toxicity. Thus, rats were subchronically exposed to MeHg in solution, selenium (Se) and fish oil, or rats were fed with a diet containing MeHg-contaminated fish. Oxidative stress biomarkers, presence of inflammation, genotoxicity, systolic blood pressure, nitric oxide (NO) levels and total mercury (Hg) and Se in different tissues were determined. Rats exposed to MeHg in solution showed endogenous antioxidants significantly reduced, increase of lipid peroxidation, hypertension, tissue inflammation, DNA damage and decrease of NO levels. MeHg+Se association presented antioxidant protection and antigenotoxic effetc, but it was not able to protect the inflammation induced by MeHg. Surprisingly, rats treated only with Se also showed increase in systolic blood pressure. MeHg+fish oil association presented a significant antiinflammatory and antigenotoxic effects and antihypertensive action; however it was not observed antioxidant capacity of fish oil. Hg absorption in different tissues was not modified by Se or fish oil treatments. On the other hand, rats fed with diet containing MeHg-contaminated fish presented few alterations in biomarkers. A lipid peroxidation biomarker showed significantly increased in rats fed with MeHgcontaminated fish as well as induction of DNA damage. From the 11th week, a hypertension was observed and NO levels did not change. In conclusion, it was observed that MeHg solution was able to induce oxidative effects, inflammation, genotoxicity and hypertension, and MeHg linked in fish induced considerable but mild effects. The chemical form that MeHg is present in fish combined with nutrients from fish, as Se and polyunsaturated fatty acids could contribute to reducing toxic effects of MeHg.

Alkyl derivatives of mercury, especially methylmercury, bring a significant risk to the environment and the human population. Methylmercury is highly toxic compound, which have the potential to bioaccumulate and biomagnify in tissues of aquatic organisms. This diploma thesis deals with issues of alkyl derivatives of mercury in biotic matrices. The goal of this thesis was to analyze fish tissues. Fish were caught from the river Svratka at the inflow and at the outflow of wastewater treatment plant. Methylmercury was determined in fish muscles and skin. Total mercury was determined in fish muscles. The extraction based on acidic digestion in hydrochloric acid and subsequent extraction with toluene was used for isolation of methylmercury from fish tissues. There was used gas chromatography with electron capture microdetector for determination of methylmercury. Total mercury was determined by special analyzer AMA 254.