TRIBUTYLTIN AFFECTS PHAGOCYTIC-ACTIVITY OF CIONA-INTESTINALIS HEMOCYTES

Organotin compounds have been used in marine anti-fouling paints as bi ocides. Because tunicates are vulnerable to these compounds in their n atural habitats, we used Ciona intestinalis to establish an assay for phagocytosis in vitro of yeast by hemocytes after exposure to differen t concentrations (0.0015, 0.015, 0.15 and 1.5 mu M) of four organotin compounds: tributyltin (TBT), triphenyltin (TPT), dibutyltin (DBT) and diphenyltin (DPT), To evaluate the phagocytic activity, we used a met hod based on fluorescence excitation of yeasts pre-treated with eosin- Y. The percentage of phagocytosis decreased from 45.1 +/- 3.49 to 22.4 +/- 5.14 at 1.5 mu M of TBT (P < 0.001); it was significantly reduced in presence of the ionophore A23187, TPT, DPT and DBT did not show si gnificant effects on phagocytosis, Because the effect of TBT was irrev ersible, differences between the inhibitory mechanisms of ionophore an d 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 exposur e to xenobiotics.