Effects of exposure to sublethal copper concentration on glyoxalase system enzymes in specimens of Scapharca inaequivalvis

The present investigation relates the changes in the activity of glyoxalase enzymes (glyoxalase I, G I, and glyoxalase II, G II) in certain tissues (foot, gills and digestive gland) of the bivalve mollusc Scapharca inaequivalvis after a two-week exposure to a sublethal concentration (1.6 μM, 0.1 ppm) of Cu++ and untreated control specimens in marine water. The trials also included determination of Cu content in the tissues and measurements of lactate dehydrogenase (LDH) activity, to estimate either possible Cu accumulation or alterations in glycolytic activity. Copper accumulation was present in all the studied organs, being 45-fold increased in the gills. G I, G II and LDH activities were unchanged in the digestive gland after Cu exposure. G I activity in foot and gills of Cu-exposed animals decreased, likely due to a drop in the glycolytic rate, as pointed out by the parallel decrease of LDH activity. After Cu exposure, G II activity was unchanged in the gills, maybe to secure enough levels of GSH; however, in the foot G II activity decreased, likely giving an increased intracellular amount of S-d-lactoylglutathione as energy supplier.