Interaction of tributyl- and triphenyltin with the microsomal monooxygenase system of molluscs and fish from the Western Mediterranean

Abstract

The in vitro interaction of tributyltin (TBT) and triphenyltin (TPhT) with the microsomal cytochrome P450 monooxygenase system of different marine organisms has been evaluated. The selected organisms were two bivalve species, the mussel Mytilus galloprovincialis and the clam Tapes decussata, and the gastropod Thais haemastoma. The fish Mullus barbatus was also studied and the results compared with those obtained for invertebrates. The microsomal fraction isolated from the hepatopancreas or liver of these organisms was incubated in the presence of different concentrations of TBT and TPhT and the interaction with cytochrome P450, cytochrome b 5, NAD(P)H cytochrome c reductases and 7-ethoxyresorufin O-deethylase (EROD) activity evaluated. Direct effects on spectrally determined P450 and b 5 were only studied in mussels and detected at very high concentrations of TBT or TPhT (1 mM). In general, TBT and TPhT differed in their specificity. TBT led to inhibition of both NADH and NADPH cytochrome c reductase activity in the studied molluscs, whereas TPhT showed little effect. On the contrary, no significant effects on fish hepatic NAD(P)H cytochrome c reductases were detected. EROD activity, however, was significantly inhibited by both TBT and TPhT in Mullus barbatus at a concentration as low as 5–10 μM. The study shows speciesrelated differences and selective effects of TBT and TPhT on different components of the microsomal monooxygenase system.