Primary cell-culture of the digestive gland of the marine mussel Mytilus edulis:: a time-course study of antioxidant- and biotransformation-enzyme activity and ultrastructural changes

A primary culture of a mixed-cell population from the digestive gland of the marine mussel Mytilus edulis L. was developed for potential use in toxicological studies. Cells were maintained for up to 2 wk in a suspension culture, and their survival rate was monitored with regard to different cell types. No cell proliferation was observed. Smaller cell types survived with a viability of >50% after 13 d in culture, whereas the larger, lysosome-containing digestive cells deteriorated rapidly (viability < 50% after 3 d). Differential survival rates of the two cell groups was confirmed by an ultrastructural analysis of cell morphology in cells cultured for up to 4 d. Electron-microscope micrographs revealed that some structural damage of digestive cells began soon after initiation of the culture, with subsequent deterioration and death. In contrast, smaller cell types such as duct epithelial cells appeared relatively healthy and dominated the cell culture. A study of antioxidant and biotransformation enzyme activities in digestive-gland cells revealed a time-course pattern of change in activity levels possibly linked to differential cell survival. The activities of the biotransformation enzymes NADH-DT diaphorase (EC 1.6.99.2), cytochrome P450-dependent benzo[a]pyrene hydroxylase and glutathione S-transferase (EC 2.5.1.18) decreased more rapidly over time than the activities of the antioxidant enzymes catalase (EC 1.11.1.6) and superoxide dismutase (EC 1.15.1.1). This possibly indicates that antioxidant enzyme activity is more stable over time than that of biotransformation enzymes and/or that the capacity of xenobiotic metabolism is primarily located in the large digestive cells, whereas antioxidant functions can be found in both digestive and smaller cell groups.