Hepatopancreas mitochondria of Mytilus galloprovincialis: effect of zinc ions on mitochondrial bioenergetics and metabolism

Oxygen uptake, respiratory complexes, and metabolic activities have been studied in mitochondria isolated from the hepatopancreata of Mytilus galloprovincialis collected in the "Mar Grande" of Taranto (Ionian Sea, Italy). Although exposure to 5.0 ?g Zn2+/L resulted in a significant increase of states 3 and 4 respiration with glutamate + pyruvate as respiratory substrate, it was found that the exposure of mussels to different concentrations of Zn2+ (2.5-7.5 ?g/L) neither inhibited mitochondrial respiration nor exerted any inhibitory effect on representative mitochondrial dehydrogenases. It rather stimulates these activities, producing an extra synthesis of adenosine triphosphate by hepatopancreas mitochondria and possibly increasing its availability in the cytoplasmic compartment. This might be considered as a specific strategy utilized by the mussel to cope with variations in the heavy metals content of the marine environment, and it could be used to detect toxic effects.