Characterization of the immunotoxicity of chlorothalonil to striped bass phagocytes following in vitro exposure

The fungicide chorothalonil (TCIN), with both agricultural and horticultural applications, is a common aquatic pollutant in the Chesapeake Bay and its tributaries. The immunotoxic potential of TCIN was investigated following 20 h in vitro exposure of striped bass (Morone saxatilus) macrophages to a range of sublethal concentrations. Cells from the anterior kidney were separated by density-gradient centrifugation to obtain phagocytes. Following TCIN exposure, reactive oxygen species (ROS) production was evaluated using luminol-augmented chemiluminescence; phagocytic capacity was measured by ingestion of FITC-conjugated yeast; and NADPH production was estimated by monitoring the reduction of a water-soluble tetrazolium, MTS. Results indicate that TCIN decreased ROS production in both zymosan- and phorbol myristate acetate (PMA)-stimulated cells in a dose-dependent manner. Significant decreases were observed with both stimulants at or above 0.9 μM. PMA-stimulated NADPH production coincident with the respiratory burst was also decreased at or above 0.9 μM. TCIN did not appear to alter phagocytic ability. Taken together, these results indicate that the mechanism of toxicity affects the activation or function of the NADPH oxidase, but not the uptake of particles by phagocytosis, and that these effects can probably be localized to the signal transduction pathway or the assemblage of NADPH oxidase.