Comparative disposition and biotransformation of pentachlorophenol in the oyster (crassostrea gigas) and abalone (haliotis fulgens)

In order to elucidate possible detoxication mechanisms, the disposition and biotransformation of pentachlorophenol (PCP, a general biocide) were compared in two marine molluscs: a bivalve, the Pacific oyster (Crassostrea gigas), and a gastropod, the green abalone (Haliotis fulgens). In a flowthrough exposure system, oysters and abalones (n = 6 each) were individually exposed to 800 and 500 μg liter of PCP in seawater, respectively, for 5 hr to determine bioconcentration and tissue distribution after short-term exposure; three individuals of each species were removed for analysis, while remaining animals were exposed to clean seawater for an additional 13 hr to allow depuration of retained residues. Retained residues were quantified by tissue digestion and liquid scintillation counting (LSC), and excreted residues were collected on XAD-4 resin and identified by high-pressure liquid cochromatography, fraction collection, and LSC. The 5-hr total concentration factor (similar to a bioconcentration factor but including both PCP and any metabolites) ranged from 25.1 to 44.5 in the oyster and from 44.5 to 63.2 in the abalone. Highest PCP tissue concentrations were 109.3 nmol g^-1 in oyster viscera and 141.6 nmol g^-1 in abalone gill; tissues retaining the greatest PCP mass were oyster viscera (41.5%) and abalone foot muscle (39.0%). During recovery, oysters depurated 95.2% of retained residues, while abalones depurated only 23.3%, with concentrations in all individual tissues of both species declining. Finally, PCP biotransformation was limited in both species, with oysters depurating only PCP (88.8%) and pentachlorophenylsulfate (11.2%), while abalones produced pentachlorophenyl-β-D-glucoside (14.7%), tetrachloro-p-hydroquinone (7.3%), and pentachlorophenylsulfate (5.5%). During short-term exposure, Pacific oysters limit the accumulation of PCP, possibly by closing their shells, and efficiently depurate retained residues to limit toxic effects. In contrast, green abalones rely more on biotransformation to detoxify residues since they can neither limit PCP accumulation nor depurate retained residues as effectively. © 1993 Academic Press.

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Author Scott Leigh Shofer Medicine, Pulmonary, Allergy, and Critical Care Medicine