Environmental pollutants such as heavy metals exert immunotoxic effects on aquatic organisms. The immune defence of molluscs is comprised of cell-mediated and humoral mechanisms, in which haemocytes play a key role. In this study, a model based on primary cultured haemocytes from the gastropod mollusc Haliotis tuberculata was established to investigate the effects of zinc in vitro. Cells were exposed for 24 h to ZnCl(2) concentrations of 0, 10, 100 or 1000 microM. The effects of zinc on haemocyte parameters were investigated using morphological, spectrophotometric and flow cytometry analysis. Immunotoxicity was reflected by a significant decrease in the number of viable haemocytes (LC(50)(24 h) = 314 microM). Moreover, the cell area was dramatically reduced, and the percentage of rounded cells increased with increasing zinc concentrations. Exposure to 1000 muM zinc induced a significant reduction in acid phosphatase activity, phagocytic activity and reactive oxygen species production in haemocytes. However, several haemocyte parameters increased significantly after 24 h of zinc exposure. In response to a 1000 microM exposure, the phenoloxidase level was 26-fold higher than that of the control, and non-specific esterase activity was increased by 69% above that of the control. These results suggest a relationship between zinc exposure and alterations in the functional responses of haemocytes from H. tuberculata.
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