Subchronic exposure to atrazine induces biochemical and histopathological changes in the gills of a Neotropical freshwater fish, Prochilodus lineatus

Abstract

The impact of acute (48h) and subchronic (14 days) exposures to environmentally realistic atrazine concentrations (2, 10 and 25μgL−1) were evaluated on the gills of Prochilodus lineatus by assessing the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), the levels of reduced glutathione (GSH) and lipid peroxide (LPO) as well as the histopathological damage. Acute and subchronic exposure to atrazine at 2 or 25μgL−1 did not change the activities of GST, SOD, CAT or GPx or the concentrations of GSH and LPO; however, subchronic exposure to 10μgL−1 increased the activity of GST, SOD and CAT and the LPO level. Histopathological indexes indicated normal gill function with scattered epithelial changes after acute and chronic exposure to 2 or 10μgL−1 of atrazine; however, fish chronically exposed to 25μgL−1 of atrazine, although had scattered lesions, the severity of lesions resulted in slightly to moderately gill damage. Acute exposure to atrazine decreased the type 3 MCs (containing acid mucosubstances with sulfate esters) in fish exposed to 2 or 10μgL−1 and increased the type 4 MCs (containing all types of mucosubstances) in fish exposed to 25μgL−1. Chronic exposure to atrazine reduced the type 3 MCs in fish exposed to 10 or 25μgL−1. The gills showed a low sensitivity to atrazine after acute exposure. However, the persistence of atrazine in water (subchronic exposure) promoted an increase of LPO levels in the gills and increased the frequency and severity of histopathological changes. The decreased density of type 3 MCs in fish exposed to atrazine suggests a mechanism to wash toxic substances away from the gill surface.