In vitro effects of tributyltin on functional responses of haemocytes in the clam Tapes philippinarum

The effects of tributyltin (TBT, as the chloride) on circulating cells from the clam Tapes philippinarum were investigated, in order to set up quick and reproducible in vitro bioassays to evaluate TBT toxicity in bivalve molluscs. Haemocytes, collected from the adductor muscle of clams, were exposed for 60 min at 25degreesC to sublethal concentrations of TBT (0.01, 0.05, 0.1 muM) and the effects on uptake of the vital dye Neutral Red, and both superoxide dismutase (antioxidant enzyme) and lysozyme (bacteriolytic enzyme) activities were spectrophotometrically evaluated. Exposure of haemocytes to 0.05 VIM TBT caused a significant increase (P < 0.05) in Neutral Red dye uptake compared with controls, whereas no differences resulted after exposure to 0.01 and 0.1 pm TBT. Enlarged lysosomes were observed in haemocytes exposed to 0.05 muM TBT. Moreover, in haemocytes treated with 0.05 pm and 0.1 muM TBT, superoxide dismutase activity significantly decreased (P < 0.05 and P < 0.01 respectively) with respect to that of controls. A significant decrease in lysozyme activity was also observed in haemocytes exposed to 0.05 (P < 0.01) and 0.1 muM TBT (P < 0.001). These results suggest a relationship between TBT exposure and alterations in functional responses of haemocytes in T. philippinarum. The proposed assays are sensitive, rapid and reproducible. They may be proposed as biomarkers, although their responsiveness needs to be more fully evaluated in haemocytes collected after clam exposure in both laboratory and field conditions. Copyright (C) 2002 John Wiley Sons, Ltd.