Residue-response relationship between PAH body burdens and lysosomal membrane destabilization in eastern oysters (Crassostrea virginica) and toxicokinetics of PAHs

Abstract

This study was undertaken to establish residue-response relationship between lysosomal destabilization and body residues of multiple PAHs in eastern oysters (Crassostrea virginica) exposed to a mixture of PAHs for 25 days in laboratory aquariums. The contaminated oysters were then placed in clean aquariums for 20 days to allow them to depurate and recover. The lysosomal destabilization was linearly correlated with the PAH body burdens. Regression analysis showed that critical body residue (CBR), in terms of lysosomal destabilization (at least 50% of destabilized cells), was found at 2,100 ng/g (9.32 nmol/g) of total PAHs. This CBR is much lower than the CBRs for reproduction and death, confirming that lysosomal destabilization, as a cellular level biomarker, appears to be functioning as an early warning indicator that can be used to detect aquatic contamination much before severe effects are observed. During 25 days of exposure, the lysosomal destabilization and PAH body burdens increased from 32 to 75% and 77 to 5,925 ng/g, respectively. After 20 days of elimination period, the lysosomal destabilization and PAH body burdens decreased to 49% and 2,350 ng/g, respectively. Uptake rates of PAHs showed parabolic shaped correlation with hydrophobicity (K ow ). Uptake rate constants of more hydrophobic PAHs (log K ow > 4.6) had a negative correlation with K ow , implying that hydrophobicity alone is not a satisfactory predictor for these PAHs. Elimination half-lives varied from 4 to 96 days and bioconcentration factors ranged from 650 to 160,000. Fugacity ratios (f o /f w ) indicated that equilibrium still was not reached at the end of the uptake period. Data obtained from the three replicate aquariums, which were operated at the same time under the same condition, showed good replicability (RPD < 30%).