Butyltins, widely used as biocides mainly in antifouling paints and wood preservatives, cause deleterious effects on marine ecosystems, particularly on filtering invertebrates such as bivalve molluscs and tunicates. Colonial ascidians are reported to be very sensitive to butyltins so that mortality occurs after exposure at concentrations higher than 100 ng/L. Besides, di- and tributyltins have been shown to interfere with immune system of mammals, causing atrophy of the thymus and lymphoid tissues, and cytolysis of PMNs after inhibition of chemotaxis and respiratory burst, with resultant depression of cell mediated immune responses. We studied the in vitro effects of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT), respectively as mono-, di- and trichloride, on the yeast phagocytosis by hemocytes of the colonial ascidian Botryllus schlosseri. A highly significant decrease of hemocyte viability (trypan blue test) was observed following an 1 hr exposure at concentrations higher than 100 µM for DBT and TBT, and 1 mM for MBT. Then the phagocytosis test was performed with the three compounds at 0.1, 1, 10 µM. The phagocytosis index was significantly reduced in the following order: DBT (1 µM), TBT (1 – 10 µM) and MBT (10 µM). The same order of inhibition was observed for Ca2+_ATPase activity. These results suggest that the inhibition of phagocytosis may be linked strictly with inhibition of Ca2+-ATase. TBT effects were thus compared with those induced by ouabain, as reference enzyme inhibitor, at a non lethal concentration (10 mM). A combined response of summation or additive effect of TBT and ouabain was demonstrated by means of cross-experiments with isodynamic mixtures, suggesting a common mechanism of action. These results were confirmed by cytochemistry of Ca2+, since the accumulation of the ion was directly proportional to inhibition of Ca2+-ATPase. Some morphological changes occurred, but without cytolysis. All these results suggest that the organotins interact with calcium pump, probably through calcium channels and calmodulin as demonstrated in mammals. As TBT is also known to inhibit mitochondrial oxidative phosphorylation, 2,4 dinitrophenol (DNP) was tested as reference enzyme inhibitor at a sublethal concentration (0.1 mM). A combined response of incomplete summation or less than additive effect was demonstrated by means f cross-experiments with isodynamic mixtures of TBT and DNP, suggesting a secondary and/or indirect mechanism of action.

Immunotoxicity of butyltins in Tunicates.

CIMA, FRANCESCA;BALLARIN, LORIANO;
1994

Abstract

Butyltins, widely used as biocides mainly in antifouling paints and wood preservatives, cause deleterious effects on marine ecosystems, particularly on filtering invertebrates such as bivalve molluscs and tunicates. Colonial ascidians are reported to be very sensitive to butyltins so that mortality occurs after exposure at concentrations higher than 100 ng/L. Besides, di- and tributyltins have been shown to interfere with immune system of mammals, causing atrophy of the thymus and lymphoid tissues, and cytolysis of PMNs after inhibition of chemotaxis and respiratory burst, with resultant depression of cell mediated immune responses. We studied the in vitro effects of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT), respectively as mono-, di- and trichloride, on the yeast phagocytosis by hemocytes of the colonial ascidian Botryllus schlosseri. A highly significant decrease of hemocyte viability (trypan blue test) was observed following an 1 hr exposure at concentrations higher than 100 µM for DBT and TBT, and 1 mM for MBT. Then the phagocytosis test was performed with the three compounds at 0.1, 1, 10 µM. The phagocytosis index was significantly reduced in the following order: DBT (1 µM), TBT (1 – 10 µM) and MBT (10 µM). The same order of inhibition was observed for Ca2+_ATPase activity. These results suggest that the inhibition of phagocytosis may be linked strictly with inhibition of Ca2+-ATase. TBT effects were thus compared with those induced by ouabain, as reference enzyme inhibitor, at a non lethal concentration (10 mM). A combined response of summation or additive effect of TBT and ouabain was demonstrated by means of cross-experiments with isodynamic mixtures, suggesting a common mechanism of action. These results were confirmed by cytochemistry of Ca2+, since the accumulation of the ion was directly proportional to inhibition of Ca2+-ATPase. Some morphological changes occurred, but without cytolysis. All these results suggest that the organotins interact with calcium pump, probably through calcium channels and calmodulin as demonstrated in mammals. As TBT is also known to inhibit mitochondrial oxidative phosphorylation, 2,4 dinitrophenol (DNP) was tested as reference enzyme inhibitor at a sublethal concentration (0.1 mM). A combined response of incomplete summation or less than additive effect was demonstrated by means f cross-experiments with isodynamic mixtures of TBT and DNP, suggesting a secondary and/or indirect mechanism of action.
Abstract book of the 3rd International Conference on Environmental and Biological Aspects of Main-Group Organometals - ICEBAMO 94
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11577/2453947
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