Morphological and functional response of Mytilus galloprovincialis exposed to the Enalapril metabolite, Enalaprilat

The increasing presence of antihypertensives and their metabolites in the aquatic environment is giving rise to considerable concern, due to their potential effects on non-target organisms. We here assessed whether and to what extent the exposure to Enalaprilat, the main metabolite of the Angiotensin Converting Enzyme (ACE) inhibitor Enalapril, induces morpho-functional alterations in the mussel Mytilus galloprovincialis. The effects of 10-days exposure to 7 ng/L (ET1) and 7000 ng/L (ET2) of Enalaprilat were analyzed in the digestive gland (DG) in terms of cell viability, and cell volume regulation, and in both DG and gills in terms of tissue morphology, oxidative stress and stress protein expression. Results indicated that Enalaprilat did not compromise the viability of DG cells and haemocytes, as well as the capacity of DG cells to regulate cell volume. Morphological analysis revealed an increase in eosinophilia, indicative of an inflammatory response activation, in the connective tissue of DG from ET1 group, and a loss of epithelial integrity in gills. No changes were observed in both DG and gill extracts in the relative transcript abundance of hsp70, neither in the relative protein expression, while a tissue-specific modulation of antioxidant enzymes CAT and SOD was observed in gills and DG. Overall, our data suggest that environmental exposure to Enalaprilat, by activating inflammatory and oxidative stress responses, may potentially affect animal homeostasis.