BREVETOXIN - TISSUE DISTRIBUTION AND EFFECT ON CYTOCHROME-P450 ENZYMES IN FISH

As part of our investigation of the metabolism of brevetoxin (PbTx) in fish, we initiated a two-part study to determine the toxin's tissue d istribution and its ability to induce xenobiotic metabolizing enzymes. In the first study, gulf toadfish (Opsanus beta) were administered C- 14-PbTx-3 orally in a fishmeal slurry and sacrificed 72 hr later. Radi oactivity was greatest in the hepatobiliary system (40% of body burden ), representing the key role this system plays in the detoxification a nd elimination of brevetoxin. Muscle tissue contained 27%, followed by gastrointestinal tract (25%). To investigate the effects of PbTx on x enobiotic metabolizing enzymes, immature redfish (Scianops ocellatus) were given two doses of brevetoxin (1.5 or 2.5 mu g/100 g body weight) or cod liver oil in a fishmeal slurry by gavage. The activities of tw o hepatic P450 enzymes, ethoxyresorufin O-deethylase (EROD) and pentox yresorufin O-depentylase (PROD), as well as the cytosolic enzyme, glut athione S-transferase (GST), were measured. At the higher dose, PbTx s ignificantly increased EROD activity. These results suggest that breve toxin is capable of inducing an important xenobiotic metabolizing enzy me (EROD).