Silva_2026_Environ.Res_303_124751

Cholinesterases (ChEs) are enzymes highly sensitive to organophosphate and carbamate pesticides, as well as heavy metals. This study evaluated the effects of these contaminants on the brain and gill acetylcholinesterase (AChE) of the catfish Cathorops spixii and its potential as a biomarker in the Goiana-Mega estuary, within the Aca-Goiana RESEX, northeastern Brazil. Specimens were collected from three estuarine sites and a preserved control area. Enzymatic characterization included pH (4-9) and temperature (5-70 degreesC) optima. In vitro exposure tests assessed the effects of metals (arsenic, copper, cadmium, lead, mercury, zinc) and pesticides (organophosphates, carbamates, benzoylurea). Water samples from the estuary were also analyzed for metals and inhibitory effects on ChE activity. Pesticides showed IC(20) values of 2.2-4104.8 microg/L (gills) and 2.01-385.65 microg/L (brain), while metals exhibited IC(20) values of 7.62-90.26 microg/L (gills) and 8.43-788 microg/L (brain), with copper and cadmium being the most inhibitory. Water from sampling points inhibited gill ChE by 89% and 63% and brain ChE by 14% and 7.76% at points 1 and 2, respectively. Metal concentrations in water exceeded regulatory limits, particularly for copper and lead. These findings indicate contamination by anticholinesterase pollutants in the estuary. The brain and gill ChEs of C. spixii demonstrate high sensitivity to pesticides and metals, supporting their use as biomarkers for monitoring aquatic pollution.