title: Brevetoxin metabolism and elimination in the Eastern oyster (Crassostrea virginica) after controlled exposures to Karenia brevis.
abstract: The metabolism and elimination of brevetoxins were examined in the Eastern oyster (Crassostrea virginica) following controlled exposures to Karenia brevis cultures in the laboratory. After a 2-day exposure period ( approximately 62 million cells/oyster), elimination of brevetoxins and their metabolites was monitored by using liquid chromatography/mass spectrometry (LC/MS). Composite toxin in oyster extracts was measured by in vitro assay (i.e. cytotoxicity, receptor binding, and ELISA). Of the parent algal toxins, PbTx-1 and PbTx-2 were not detectable by LC/MS in K. brevis-exposed oysters. PbTx-3 and PbTx-9, which are accumulated directly from K. brevis and through metabolic reduction of PbTx-2 in the oyster, were at levels initially (after exposure) of 0.74 and 0.49 microg equiv./g, respectively, and were eliminated largely within 2 weeks after dosing. PbTx-7 and PbTx-10, the reduced forms of PbTx-1, were non-detectable. Conjugative brevetoxin metabolites identified previously in field-exposed oysters were confirmed in the laboratory-exposed oysters. Cysteine conjugates of PbTx-1 and PbTx-2, and their sulfoxides, were in the highest abundance, as apparent in LC/MS ion traces, and were detectable for up to 6 months after dosing. Composite toxin measurements by in vitro assay also reflected persistence (up to 6 months) of brevetoxin residues in the oyster. Levels of cysteine conjugates, as determined by LC/MS, were well correlated with those of composite toxin, as measured by ELISA, throughout depuration. Composite toxin levels by cytotoxicity assay were well correlated with those by receptor binding assay. Cysteine-PbTx conjugates are useful LC/MS determinants of brevetoxin exposure and potential markers for composite toxin in the Eastern oyster.
authors.affiliation: Gulf Coast Seafood Laboratory, US Food and Drug Administration, P.O. Box 158, 1 Iberville Drive, Dauphin Island, AL 36528-0158, USA. splakas@cfsan.fda.gov
authors.forename: Steven M
authors.initials: SM
authors.lastname: Plakas
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Wang
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: El Said
authors.forename: Edward L E
authors.initials: EL
authors.lastname: Jester
authors.forename: Hudson R
authors.initials: HR
authors.lastname: Granade
authors.forename: Leanne
authors.initials: L
authors.lastname: Flewelling
authors.forename: Paula
authors.initials: P
authors.lastname: Scott
authors.forename: Robert W
authors.initials: RW
authors.lastname: Dickey
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001681:Biological Assay; D002853:Chromatography, Liquid; D018736:DNA Adducts / Q000737:chemistry; D004141:Dinoflagellida / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D008387:Marine Toxins / Q000378:metabolism* / Q000633:toxicity; D013058:Mass Spectrometry; D051379:Mice; D010125:Ostreidae / Q000378:metabolism*; D035964:Oxocins / Q000378:metabolism* / Q000633:toxicity; D051381:Rats; D014316:Tritium; D000095702:Polyether Toxins
chemical_list: D018736:DNA Adducts; D008387:Marine Toxins; D035964:Oxocins; D014316:Tritium; C041017:brevetoxin T17; D000095702:Polyether Toxins; C053342:brevetoxin