Uptake of cadmium and zinc by the mussel Mytilus edulis and inhibition by calcium channel and metabolic blockers

The mussel Mytilus edulis is extensively used to monitor metal contaminatio n of estuarine and marine systems. Nonetheless, the mechanisms of metal upt ake are poorly understood. To characterise the systems involved in cadmium and zinc uptake, the interaction between the two metals and the effects of different calcium channel blockers (diltiazem, nifedipine, verapamil) and i nhibitors of active transport and metabolism (ouabain, sodium cyanide, 2,4 dinitrophenol) on the uptake of calcium, cadmium and zinc in Mytilus edulis have been studied. To separate direct from indirect effects of the inhibit ors on metal uptake, their influence on the physiological condition of the mussels was also investigated. This was done by measuring clearance, respir ation and excretion rates under the different exposure regimes and determin ing the scope for growth as an integrative index for physiological conditio n. The study has shown that the uptake of cadmium and zinc by Mytilus eduli s can be modulated by calcium channel blockers and other inhibitors. The in hibitors also influenced physiological condition, but a significant correla tion with the effects on metal uptake did not exist in most cases. Cadmium and zinc also inhibit each other's uptake, but the type of inhibition is no t yet clear. The effects of the inhibitors on cadmium and zinc uptake are v ery different from the effects on calcium uptake, indicating that cadmium a nd zinc are preferentially taken up through other gateways. Overall, a sign ificant degree of linear association is found between the effects of the in hibitors on the uptake of cadmium and zinc, suggesting common uptake routes . In addition, the effects of the calcium channel antagonist on the uptake of the metal ions are organ dependent, indicating that other types of chann els are involved in the uptake of the metal ions in the gills and digestive system.