Subchronic effects of environment-like cadmium levels on the bivalve Anodonta anatina (Linnaeus 1758): III. Effects on carbonic anhydrase activity in relation to calcium metabolism

The effects of subchronic cadmium (Cd exposure at environment-like levels (water- and algae-borne Cd) on carbonic anhydrase (CA), its distribution in various body compartments and subcellular fractions, and its correlation to Cd and Ca concentrations in the freshwater mussel Anodonta anatina were investigated. CA activity in the hemolymph (HML) and extrapallial fluid were strongly affected in both directions, i.e. inhibition and then induction depending on the length of exposure and depuration. Cd also lowered total and subcellular CA activity in all tested tissues, especially in the digestive gland and gills. These effects were confirmed by negative correlation of both total and cytoplasmic CA activity relative to newly incorporated Cd. The specific activity of total CA was correlated to Ca in the HML and in the mantle but not in other compartments. These observations suggest that Cd exerted indirect effects on ion regulation and Ca homeostasis through its effects on CA, perhaps constituting the physiological basis of Cd-toxicity in this freshwater bivalve.