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2L - Immunotoxicity - genotoxicity - ED (WEP/121) Effects of environmental concentrations of atrazine on hemocyte density and phagocytic activity in the pond snail Lymnaea stagnalis. Russo, J.1, 2, Lagadic, L.2, 1 Université de Rennes, Rennes, France2 INRA EQHC, Rennes, France ABSTRACT- Immunotoxicological effects of long-term, semi-static exposure to environmental concentrations (10, 23, 50 and 100 Key words: phagocytosis, immunotoxicity, oxydative stress, flow cytometry |
g/L) of atrazine were studied in the pond snail. Non-invasive hemolymph sampling was performed at elapsed times (0, 24, 48, 72, 96, 168, 336, 504 and 672 hrs) during exposure. Immunological responses were assessed through total and differential hemocyte counts, phagocytosis of latex beads and Escherichia coli, and phorbol 12-myristate 13-acetate (PMA)- or E. coli-stimulated production of reactive oxygen species (ROS). Over the whole exposure period, every atrazine concentration induced a significant increase of the mean total number of hemocytes, but no concentration-response relation was observed. A significant 1.6-fold increase was observed after 96 hrs of exposure to atrazine, whatever the concentration. Following long-term (504 hrs) exposure, total hemocyte density remained higher only in the snails exposed to the two highest concentrations, as compared the controls. All atrazine concentrations resulted in significant increases in the number of granulocytes, indicating that these phagocytosing cells contributed most to the increases in hemocyte density in exposed snails. Both short- (24 and 96 hrs) and long-term (504 hrs) exposures had no effect on phagocytosis of latex beads, while inhibited with E. coli. Inhibition of ROS production was observed in E. coli-stimulated cells, with a significant concentration-dependent relation after short-term exposure to atrazine ; inhibition was still significant in the snails exposed to the two lowest herbicide levels after 504 hrs. Phagocytosis and oxydative burst remained unchanged in PMA-stimulated hemocytes whatever duration of exposure. Using atrazine as a model contaminant, this study emphasizes the potential of immunological responses as biomarkers of exposure of lymnaeid snails to surface water contaminating pesticides.