Made available in DSpace on 2014-12-17T14:14:04Z (GMT). No. of bitstreams: 1 GeorgeESC.pdf: 1518565 bytes, checksum: bcd5e83ea0cd501b6573d93e3ef15380 (MD5) Previous issue date: 2005-11-03 / Funda??o de Amparo a Pesquisa do Estado da Bahia / Aim: The aim of this work was to investigate the hypothesis that catechol and 3MC inhibit FADH2-linked basal respiration in mitochondria isolated from rat liver and brain homogenates. Moreover, catechol ability to induce DNA damage in rat brain cells through the comet assay (alkaline single-cell gel electrophoresis assay) was also observed. Methods: Two different catechols were evaluated: pirocatechol (derived from benzene) and 3-methylcatechol (derived from toluene); rat liver and brain homogenates were incubated with 1mM catechol at pH 7.4 for up to 30 minutes. After that, mitochondrial fractions were isolated by differential centrifugation. Basal oxygen uptake was measured using a Clark-type electrode after the addition of 10 mM sodium succinate for a period of 12 minutes. In additional experiments, rat brain cells were treated with 1, 5 and 10mM pirocatechol for up to 20 minutes at 37? C, and submitted to electrophoresis. Results: Catechols (pirocatechol and 3methylcatechol) induced a time-dependent partial inhibition of FADH2-linked basal mitochondrial respiration. Indeed, pirocatechol was able to produce a dosedependent DNA oxidative damage in rat brain cells by 2 and 4 injury levels. These results suggest that reactive oxygen species generated by the oxidation of catechols, induced an impairment on mitochondrial respiration and a DNA damage, which might be related to their citotoxicity. Conclusion: Catechols produced an inhibition of basal respiration associated to FADH2 in isolated liver and brain mitochondria; 3-methylcatechol, at the same concentration, produced similar toxicity in the mitochondrial model. Indeed, pirocatechol induced a DNA damage in rat brain cells, mainly observed in comets formation and consequent DNA degradation / Objetivo Testar a hip?tese de catec?is inibirem a respira??o basal associada ao FADH2 em fra??es mitocondriais hep?ticas e cerebrais de rato. Tamb?m, procurou-se estudar a ocorr?ncia de danos no DNA induzidos por catecol em c?lulas de c?rebro de ratos. M?todos: Foram avaliados dois catec?is: O pirocatecol (derivado do benzeno) e o 3-metilcatecol (derivado do tolueno); Os homogeneizados de f?gado e c?rebro de ratos foram incubados com catecol a 1 mM em pH fisiol?gico. Depois disso, as fra??es mitocondriais foram isoladas por centrifuga??o diferencial. O consumo basal de oxig?nio foi medido com um eletrodo do tipo Clark ap?s inje??o de succinato a 10 mM, e o consumo foi observado por 12 minutos. Em experimentos adicionais, amostras de tecidos cerebrais foram tratadas com pirocatecol em diferentes concentra??es (1 mM, 5 mM e 10 mM), durante 0 (sem incuba??o), 10 e 20 minutos a 37?C, e posteriormente submetidas a el etroforese. Resultados: Os resultados demonstram que os catec?is induziram uma inibi??o parcial da respira??o basal mitocondrial associada ao FADH2 de forma dependente do tempo. J? no caso dos experimentos com o ensaio cometa, os dados obtidos demonstram um aumento na ocorr?ncia de cometas de n?veis 2 a 4 de forma dose dependente, sugerindo que as esp?cies reativas de oxig?nio geradas pela oxida??o do catecol induzem danos de DNA, o que pode tamb?m estar relacionado com citotoxicidade deste composto. Conclus?o O pirocatecol produz inibi??o da respira??o basal associada ao FADH2 em mitoc?ndrias isoladas de f?gado e c?rebro de ratos; o 3-metilcatecol, nessa mesma concentra??o, produziu toxicidade semelhante no modelo mitocondrial. Adicionalmente, o pirocatecol induziu a um dano de DNA em c?lulas cerebrais de ratos, observado na forma??o de cometas e conseq?ente degrada??o do DNA