Tissue-specific differences in accumulation of stress proteins in Mytilus edulis exposed to a range of copper concentrations.

This study examines the expression and accumulation of two major stress proteins, stress70 and chaperonin60 (cpn60), in the gill and mantle of blue mussels, Mytilus edulis, which were exposed to a range of Cu concentrations for 7 days. Scope-for-growth (SFG), mortality, and Cu accumulation in gill and mantle tissue were also measured to monitor the physiological effects of Cu exposure in the organisms. In general Cu accumulated to a greater extent in gill relative to mantle tissue. A reduction of SFG index and increased mortality was also observed at the two highest Cu concentrations. We found no significant differences between the two tissues in the expression of cpn60 and stress70 for mussels exposed to Cu ranging from 0 to 10 micrograms/liter Cu (cpn60) and 0 to 32 micrograms/liter Cu (stress70) in sea-water. However, differences in the stress response were observed between the gill and the mantle tissue of mussels exposed to higher Cu concentrations. Chaperonin concentrations were greater than an order of magnitude higher in the gill than in the mantle for these mussels. Further, although the accumulation of stress70 was similar between the two tissues, two additional proteins reacted with antibody to stress70 in gill, but not mantle tissue, of mussels exposed to 100 micrograms/litter Cu. This study suggests that the physiological processes involved in contaminant uptake, distribution, and detoxification may affect the tissue-level expression of the stress response in multicellular organisms. Further, the intensity of the stress response and relative concentrations of chaperonin and stress70 among tissues may help identify tissues which are the most vulnerable to damage caused by a particular environmental stressor.