Adenylate energy charge and metallothionein as stress indices in Mytilus galloprovincialis exposed to cadmium and anoxia

Cadmium was rapidly concentrated by Mytilus galloprovincialis (Mollusca: Bivalvia) during one week's exposure to 0.5 mu g Cd ml(-1) sea-water. Cadmium accumulation was determined in the gills, adductor muscle and viscera. The amount of cadmium bound to metallothionein (MT) provided a specific index of exposure to this metal. Maximum values were reached in viscera; this observation is consistent with the presence, in the viscera, of the hepatopancreas which is commonly regarded as a major site for MT synthesis. In tissues of M. galloprovincialis exposed to Cd different energy charge (AEC) responses were observed. Adenylate energy charge (AEC) values appeared to be more affected by Cd exposure in adductor muscle than in the gills and viscera. These variations could be related to an impairment of oxidative metabolism leading to a partial switch from aerobic to anaerobic metabolism. The data obtained from anoxic incubation did not show significant differences in AEC values between pre-exposed and untreated animals, with the sole exception of adductor muscle of exposed mussels.