Tributyltin affects phagocytic activity of Ciona intestinalis hemocytes

Organotin compounds have been used in marine anti-fouling paints as biocides. Because tunicates are vulnerable to these compounds in their natural habitats, we used Ciona intestinalis to establish an assay for phagocytosis in vitro of yeast by hemocytes after exposure to different concentrations (0.0015, 0.015, 0.15 and 1.5 microM) of four organotin compounds: tributyltin (TBT), triphenyltin (TPT), dibutyltin (DBT) and diphenyltin (DPT). To evaluate the phagocytic activity, we used a method based on fluorescence excitation of yeast pre-treated with eosin-Y. The percentage of phagocytosis decreased from 45.1 +/- 3.49 to 22.4 +/- 5.14 at 1.5 microM of TBT (P < 0.001); it was significantly reduced in presence of the ionophore A23187. TPT, DPT and DBT did not show significant effects on phagocytosis. Because the effect of TBT was irreversible, differences between the inhibitory mechanisms of ionophore and TBT are suggested. These results indicate that for future analyses, tunicates should become excellent models for dissecting events such as phagocytosis that are associated with immunosuppression after exposure to xenobiotics.