Effects of 2,4-dichlorophenoxyacetic acid (2,4-d) on the liver and kidney of Tropidurus torquatus (Squamata, Tropiduridae)

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is widely used in tropical agriculture, yet its effects on non-target ectothermic vertebrates remain poorly understood. This study assessed the subchronic toxicological impact of 2,4-D on the liver and kidneys of Tropidurus torquatus, a neotropical lizard commonly found in agricultural areas. Seventeen adult males were divided into control (n = 9) and treatment (n = 8) groups. The treated group received 0.01 mg/kg body weight/day of 2,4-D orally for 30 days, based on the acceptable daily intake for mammals. Histopathological, stereological, and biochemical analyses were conducted. Hepatic histopathology showed no significant alterations, but stereology revealed a reduction in hepatocyte volume fraction in treated animals (p < 0.05). Renal histopathology showed significant degenerative changes, including hydropic-vacuolar degeneration, coagulative necrosis, and accumulation of brownish granular pigment (p < 0.0001). Biochemically, 2,4-D exposure triggered oxidative stress in both organs, with increased reactive oxygen species and lipid peroxidation, and reduced activities of superoxide dismutase and catalase. Despite these functional changes, renal stereology showed no significant differences in kidney volume or glomerular count. These findings indicate that even at doses considered safe for mammals, 2,4-D causes subclinical but relevant toxic effects in reptiles. This highlights the limitations of extrapolating mammalian safety thresholds to other taxonomic groups and reinforces the need for specific ecotoxicological assessments focused on tropical herpetofauna.