In vivo and in vitro inhibition of CYP1A enzymes activity by 2,4,6-trinitrotoluene (TNT) in European eel Anguilla anguilla

The present research was carried out in order to investigate the interaction of 2,4,6-trinitrotoluene (TNT) with CYP1A catalytic enzymes in specimens of European eel (Anguilla anguilla L.). An in vivo experiment was performed on juveniles exposed for 6 h and 24 h to 0.5, 1 and 2.5 mg/L nominal concentrations of TNT. Catalytic activity of CYP1A enzymes such as 7-ethoxyresorufinO-deethylase (EROD) and methoxyresorufin-O- deethylase (MROD) was investigated in liver microsomal fraction of in vivo exposed eels; an in vitro study was also performed with the same TNT concentrations by using control eels. Significant inhibition of EROD activity was observed in vivo after 6h (36%) at the lowest concentration of 0.5 mg/L but not increasing at higher concentrations. A more evident significant inhibition of EROD activity was observed at 24h (55%) with the same trend starting from 0.5 mg/L. On the opposite, MROD activity was not affected after 6h of exposure while a significant inhibition was observed at 24h starting from the lowest exposure concentrations (64%). No further inhibition was evident at the highest concentrations (1 and 2.5 mg/L). The in vitro exposure confirmed the inhibition of EROD and MROD catalytic activities by TNT: both the enzymes activity resulted significantly inhibited (26%) but only at the highest concentration of 2.5mg/L. An irreversible inhibition at both enzyme level (EROD and MROD) by TNT might be hypothesised in European eels on the base of the absence of recovering of catalytic activities despite further adding NADPH during in vitro kinetic assay.