The ecotoxicological effects of diclofenac and gentamicin on Mytilus galloprovincialis: What does in vivo reveal that in vitro fails to show?

This study investigated the toxicological effects of diclofenac (DIC) and gentamicin (GEN) on the gills (G) and digestive gland (DG) of Mytilus galloprovincialis through in vitro and in vivo assays. Biochemical markers related to oxidative stress, metabolic capacity, and neurotoxicity were evaluated at the end of each assay. For both assays, principal coordinates analysis (PCO) highlighted distinct biochemical profiles between G and DG, mostly related to higher basal values for several biomarkers in DG.The Integrated Biomarker Response (IBR) index revealed the highest scores in G for the in vitro assay, especially after exposure to GEN. In the in vivo assay, instead, the highest scores were recorded in DG, particularly in response to DIC. The distinct responses of G and DG underscore their respective roles in respiration and detoxification, with G being more sensitive to acute stress and DG exhibiting greater adaptive capacity over time. Furthermore, GEN appeared to cause the greatest impact on G in the in vitro assay, while DIC had the most significant effect on DG following the in vivo experiment. In vitro assays demonstrated limited oxidative stress and cellular damage, while in vivo results highlighted substantial metabolic depression and biomarker variability under prolonged exposure. When analyzed individually, the in vitro assay showed a clearer distinction between the two contaminants, particularly in DG. The findings underscore the differential vulnerability and adaptive capacities of G and DG, attributed to their distinct physiological functions. These results emphasize the complementary nature of in vitro and in vivo approaches, with the former providing mechanistic insights and the latter reflecting systemic organismal responses. This study highlights the importance of a multi-dimensional approach, combining both in vitro and in vivo methodologies, to better understand tissue-specific toxicity and the broader ecological consequences of pharmaceutical contamination.