Efeitos da contaminação por metais pesados e biomarcadores de impacto ambiental em peixes da bacia do rio São Francisco, MG

Abstract

Heavy metals are inorganic elements that can cause serious health problems in living organisms in general. Through industrial, rural and domestic waste, metals such as Cadmium (Cd), Lead (Pb), Copper (Cu), Chromium (Cr), Iron (Fe) and Zinc (Zn) constantly reach aquatic environments. These pollutants are usually not naturally degraded and have a high capacity of bioaccumulation in tissues and organs inducing pathologies. Due this environmental problem, the objective of the present study was to evaluate, through histological and immunohistochemical analyzes, the condition of contamination of dourado, Salminus franciscanus, a large fish species, endemic to the São Francisco River Basin, MG, which represents a high commercial value and is widely consumed in population feeding. Levels of Cd, Cr, Cu, Fe, Pb and Zn was quantified in the liver and muscle tissue, of 68 specimens of S. franciscanus collected from two rivers of the São Francisco River Basin, MG, Brazil: Abaeté (low anthropic activity) and Paraopeba, sites A and B (high anthropic activity). Histopathological alterations in the liver and spleen (organs of intense metabolism) and expression of three proteins currently considered biomarkers of environmental impact, were evaluated: Metallothionein (MT), Heat Shock Protein-70 (HSP70) and Cytochrome P450-1A (CYP1A). The results evidenced that fish from the Paraopeba river are inappropriate for human consumption, exceeding the safe limits for muscle consumption (Cd, Cr, Cu and Pb above the permitted limit) established by the World Health Organization (WHO) and the Agência Nacional de Vigilância Sanitária (ANVISA). In addition to the high levels of heavy metals registered in fish muscles, in liver the values were recorded above the legal limit for Cd, Cr, Cu, Fe, Pb and Zn metals (all metals analyzed) and histopathological alterations in liver and spleen were recorded and quantified, indicating significant differences in the poor environmental quality and the scenario of high contamination by heavy metals found in Paraopeba River. Significant differences in expression levels of MT, HSP70 and CYP1A proteins, were also recorded between the Abaeté and Paraopeba Rivers, evidencing the high contamination in both sampling sites of Paraopeba River in relation to Abaeté River.