PCBs are potential genotoxicants and inductors of increased levels of ROS and oxidative stress in both
humans and wildlife. In this study, biotransformation parameters and antioxidant (AO) enzymes were
analyzed in the Asian clam, Corbicula fluminea, with respect to the presence of dioxin-like PCBs (dl-PCBs)
in the environment. For this purpose, clams were collected from three localities with different environmental
conditions. Sediments from each locality and clam tissues were analyzed for the presence
of dl-PCBs. Biological responses included changes in the expression of fish CYP1A immunoreactive protein,
changes in the activities of AO enzymes, SOD, CAT, GR and GPx, and the phase II biotransformation
enzyme GST. Clams from the locality with the highest WHO–TEQ values for sediment dl-PCBs had the
highest WHO–TEQ values for tissue dl-PCBs and the highest level of fish CYP1A immunoreactive protein
expression. The correlations found between the concentrations of dl-PCBs and AO and GST activities
revealed both concentration-dependent inhibitory and stimulatory effects. The activities of GPx, GR and
GST were very sensitive to environmental xenobiotics, including dl-PCBs. The obtained results indicate
that the activities of these enzymes were fine-tuned to provide optimized antioxidant responses. We
also observed seasonal changes in GST and AO enzyme activities in Asian clam. The highest levels of
activity were observed in spring as compared to summer or autumn. CDA, which was performed in order
to classify the different clam populations, revealed a coordinated rearrangement of the clams’ metabolic
components that were probably aimed at compensating for environmental fluctuations. The presented
data reveal the sensitivity of C. fluminea to the presence of dl-PCBs in the environment and support the
use of this clam as a sentinel species for biomonitoring studies.