Protein expression signatures and lysosomal stability in Mytilus edulis exposed to graded copper concentrations

Protein expression and lysosomal stability were observed in Mytilus edulis exposed to 0, 20, 40, 60, and 80 ppb copper sulfate for 24 h in a static exposure system. Haemolymph was removed from each mussel and analyzed for lysosomal damage using the Neutral Red retention assay expressed as the ratio of lysosomal size to cell area, the lysosomal destabilization ratio. Gill tissue from the same individuals was dissected, homogenized and the proteins extracted and then separated using two-dimensional gel electrophoresis. Two-dimensional protein maps from each concentration were analyzed using MELANIE II 2D gel analysis software (Biorad). Lysosomal damage increased with each dosage, with LDRs ranging from 0.18±0.01 at 0 ppb copper sulfate to 0.32±0.11 at 80 ppb copper sulfate. Orthogonal comparisons showed that the control, 20 and 40 ppb classes together differed significantly (P<0.05) from the 60 and 80 ppb classes together. Specific protein expression signatures were identified at each dosage.