INVESTIGATIONS ON THE BIOTRANSFORMATION CAPACITY OF ORGANOPHOSPHATES IN THE MOLLUSK DREISSENA-POLYMORPHA P

Microsomes of Dreissena polymorpha were able to biotransform the organ ophosphates thiometon and disulfoton significantly after 1 h incubatio n at 10 degrees C. Contrarily to vertebrates, biotransformation with m ussel microsomes occurred without the addition of reduction equivalent s (NADPH), at a considerably lower extent however. Metabolites of thio meton and disulfoton were detected with gas chromatography/mass spectr ometry (GC/MS) analysis: The P450 content of whole mussel tissue was 8 pmol mg(-1) protein being two orders of magnitude lower than the amou nts measured in mammal liver. Ethoxycoumarin deethylase (ECOD) activit y could be measured at 10 degrees C in microsomes of Dreissena (22 pmo l min(-1) mg(-1) protein) but not at 37 degrees C. ECOD activity was i nhibited in the presence of NADPH (measured activity 3 pmol min(-1) mg (-1)).