Evaluation of the cytotoxic effects of chlorpyrifos ethyl in fish cell lines

Chlorpyrifos-ethyl (CPE) is a widely used organophosphate pesticide that poses a significant risk to aquatic ecosystems. The present study aimed to investigate the cytotoxicity of CPE on two fish cell lines: rainbow trout gonad (RTG-2) and common carp epithelioma (EPC). The cells were exposed to a range of CPE concentrations (0.488 - 250 ppm) for 24 h. Cytotoxicity was evaluated using two complementary colourimetric assays, MTT and Neutral Red (NR), which measure mitochondrial activity and lysosomal membrane integrity, respectively. The results demonstrated that CPE induced a significant, concentration-dependent decrease in both assays in both cell lines. The calculated half-inhibitory concentration (IC50) values for the RTG-2 and EPC cells showed variations, indicating differences in sensitivity between the cell types and the metabolic endpoints assessed. The cell morphologies were changed when exposed to CPE concentrations in both cell lines. The in vitro cytotoxicity data were consistent with the acute toxicity ranges (LC50) reported in the literature for in vivo fish species, validating the use of these piscine cell lines as reliable and ethical tools for the preliminary ecotoxicological screening of pesticides. This study confirms the high cytotoxic potential of CPE and underscores the utility of fish cell lines in environmental risk assessment.