Effects of atrazine on the gill cells and ionic balance in a neotropical fish, Prochilodus lineatus.

Abstract The effects of the herbicide atrazine on the gill of the freshwater fish Prochilodus lineatus were evaluated after exposure of fish to 2, 10 and 25 μg L −1 atrazine during 48 h (acute exposure) and 14 d (subchronic exposure). Ions and osmolality were measured in plasma and gill samples were taken to determine the Na + /K + -ATPase (NKA) and carbonic anhydrase (CA) activities and for morphological analysis. Plasma osmolality and Na + and Cl − ions changed depending on atrazine concentration, but atrazine exposure had no effect on the Na + /Cl − ratio. NKA activity did not change after atrazine exposure, but CA activity decreased in fish exposed to 25 μg L −1 for 14 d. Gill MRC density decreased after acute exposure but did not change in fish exposed to the subchronic treatment. The MRC density at the epithelial surface increased in fish exposed to 25 μg L −1 , and the MRC fractional area (MRCFA) increased in fish exposed to 10 μg L −1 . The changes in MRCs provide evidence of morphological adjustments to maintain ionic homeostasis in spite of the inhibition of CA activity at the highest atrazine concentration.