Avaliação da influência da ingestão de lixo plástico nos indicadores de estresse oxidativo no sangue de tratarugas verdes (Chelonia mydas)

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Ecologia, Florianópolis, 2012O presente estudo analisou biomarcadores de estresse oxidativo, como as enzimas catalase (CAT), superóxido dismutase (SOD), glutationa peroxidase (GPx), glutationa redutase (GR) e glutationa S-transferase (GST), níveis de glutationa reduzida (GSH), de proteínas carboniladas (PC) e de lipoperoxidação (TBARS), presentes no sangue de tartarugas verdes (Chelonia mydas), vítimas de ingestão de lixo plástico, bem como o peso e volume dos resíduos ingeridos. A obstrução no trato gástrointestinal decorrente promove processos de isquemia-reperfusão associados ao estresse oxidativo sistêmico. Foram amostradas 27 tartarugas, coletadas na região da Ilha de Santa Catarina, Florianópolis, SC. Após a coleta sanguínea realizada durante exame clínico, quando se observou a presença/ausência de alguns sintomas. As tartarugas foram mantidas em tanques individuais e observadas diariamente para a constatação de lixo plástico em suas fezes: os indivíduos que realizaram três evacuações consecutivas livres de lixo plástico e não apresentaram nenhum sintoma formaram o grupo controle (n=7); os indivíduos que apresentaram as mesmas condições do grupo controle, porém em que foi constatado lixo plástico em suas fezes ao menos em uma das evacuações, foram considerados do grupo 2 (n=10); os indivíduos que apresentaram ao menos um dos sintomas avaliados durante o exame clínico e também lixo plástico em ao menos uma das evacuações, foram consideradas do grupo 3 (n=10). Foi verificada a presença de lixo plástico em 74% das tartarugas amostradas e um alto índice de ingestão de resíduos foi verificado em tartarugas sem sintomas (63%). Houve uma diferença significativa, em termos estatísticos, em relação à massa e o volume de resíduos ingeridos entre os grupos 2 e 3 (pAbstract : The aim of this study was to analyze oxidative stress biomarkers such as the enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) e glutathione S-transferase (GST), levels of reduced glutathione (GSH), protein carbonyls (PC), lipoperoxidation (TBARS), in the blood of green turtles (Chelonia mydas) victims of plastic debris ingestion, as well as measuring weight and volume of such material. The consequent gastrointestinal obstruction promote an ischemia-reperfusion process associated with systemic oxidative stress, A total of 27 turtles were collected in the region of the Island of Santa Catarina, SC. After blood collection performed during clinical examination, which showed the presence/absence of some symptoms, the turtles were kept in individual tanks and were observed daily for confirmation of plastic debris in their feces: animals that underwent three consecutive evacuations free of plastic debris and that showed no symptoms formed the control group (n=7); those that exhibited similar conditions as in the control group but presented plastic debris in their feces at least in one of the evacuations, were considered group 2 (n=10); and individuals that showed at least one symptom evaluated during clinical examination and also plastic debris in at least one of the evacuations were considered in group 3 (n=10). The presence of plastic debris was detected in 74% of the turtles sampled and a high intake of residues in turtles without symptoms (63%) was also observed. The mean weight and volume of plastic debris ingested by this group were 0.8 g and 3.0 ml, respectively. There was a significant difference regarding mass and volume of waste taken between group 2 and 3 (p<0.0007 and p<0.002, respectively). The volume of waste ingested and the enzyme activities of GPx (R=-0.48) and GR (R=-0.69) were negatively correlated. In group 2, only CAT activity showed a significant decrease (p=0.02), while GR activity showed a significant increase (p=0.04), compared to controls. No statistical variation was detected for the biomarkers studied in animals from group 3 compared to controls, only a tendency of increase in TBARS and PC levels. The means of plastic debris ingested by group 3 were 11.02 g and 19.65 ml, respectively. The results found in this study suggest that the amount of waste ingested by animals in group 2, which presented a survival rate of 100%, was not enough to cause an ischemia-reperfusion of the intestine sufficient to promote a pronounced oxidative stress. The catalase activity was apparently sufficient to detoxify the excess of H2O2. On the other hand, the high mortality of group 3 (100%) seemed to be related to the failure of antioxidant defense system, because the deleterious consequences from the oxidative stress associated with the ischemia-reperfusion injury of the gastrointestinal tract. The development of biomarkers of oxidative stress to assess the health status of marine turtles may provide an important tool in the conservation of these species