Effects of Organotins on Mixed Function Oxygenase in Shellfish and Fish with in vitro Exposure Experiment

Abstract

This study was carried out to measure the in vitro interaction of trialkyltin with the microsomal monooxygenase (MFO) system of the clam, Coelomactra antiquata. Cytochrome P450 (CYP) level and EROD activity were investigated in the microsome isolated from digestive gland of the clam exposed to tributyltin chloride (TBTC), bis-tributyltin oxide (TBTO) and triphenyltin chloride (TPTC). The specific contents of CYP in clam microsome exposed to 0.4 mM TBTC, TBTO and TPTC for 20 minutes were decreased 52, 72 and 40%, respectively, compared to control group. The EROD activities also were inhibited by exposure to TBTO (92%) and TPTC (85%) except for TBTC. The level of CYP and the EROD activities were decreased according to the OTC exposure concentrations. The toxic effects on the level of CYP and the EROD activities were in order of TPTC > TBTC > TBTO in this study. The measurement of CYP level and EROD activity could be applied as a biomarker for environmental study.Effects of tributyltin chloride (TBTC) in vitro on mixed function oxygenase (MFO) system on liver microsome of eight marine fish species were also investigated. To determine the effects on MFO system, cytochrome P450 (CYP) and cytochrome b5 contents, activities of two reductases (NADH-cytochrome b5 reductase and NADPH-cytochrome P450 reductase) and four dealkylation enzymes (EROD, PROD, MROD and ECOD) were measured in fish microsomes exposed to TBTC for 20 min. The CYP content was reduced to 10% of the control group in 6 out of 8 species exposed to TBTC, whereas there was no significant change in the cytochrome b5 content. The response of NAD(P)H dependant reductases depended on fish species. The dealkylation enzyme activities in microsome were also apparently inhibited by TBTC. The degree of inhibition was different among fish species and four enzymes. The EROD activities in eight species were decreased to the range of 1∼65% of control group.