Stability of lysosomal and cell membranes in haemocytes of the common mussel (Mytilus edulis): effect of low temperatures

Expanding industrial activities in the Arctic require an urgent assessment of the toxicity of chemicals at low temperatures. Organisms acclimatized to low temperature exhibit specific adaptations. For example, the amount of u nsaturated lipids is increased to maintain the fluidity of the cell membran es. It has been hypothesized that such temperature-induced alterations in m embrane lipid composition may affect the stability of lysosomal and cell me mbranes in the common mussel, Mytilus edulis, an organism exposed to season al temperature extremes, As mussels may be exposed to petroleum compounds a long industrialized coastlines, we tested the combined effects of exposure to low temperature and the petroleum compound, phenanthrene, on haemocyte m embrane stability. Test animals, acclimated to either 0 or 10 degreesC, wer e exposed to phenanthrene (0 = control or 500 mug l(-1)) and haemocytes wer e examined using the neutral red retention assay (lysosomal stability) and a fluorescence assay (cell membrane stability). At 0 degreesC, lysosomal an d eel membranes from uncontaminated mussels were destabilized compared with 10 degreesC (P = 0.0005). No significant effects (P > 0.05) of phenanthren e were detected at either temperature. Possible mechanisms underlying membr ane destabilization include a weaker physical resistance of the membrane du e to a higher amount of unsaturated lipids, a potentially higher level of r eactive oxygen radicals at low temperature and the higher susceptibility of unsaturated lipids to oxidative stress. More work is required to better un derstand the consequences of this membrane destabilization at low temperatu re on the susceptibility of the organism to pollutants. (C) 2000 Elsevier S cience Ltd. All rights reserved.