Tissue disposition of benzo[A]pyrene in blue mussel (Mytilus edulis) and effect of algal concentration on metabolism and depuration

Abstract

In vivo metabolism and depuration of benzo [a]pyrene (BaP) was studied in the blue mussel Mytilus edulis. In one experiment, the animals were injected with 3H‐BaP and thereafter exposed to either a high (H) or a low (L) concentration of the alga Isochrysis galbana. Mussels were sampled after 2, 4, 8, 16, and 32 d and temporal changes in the metabolite profiles were analyzed using nonpolar and polar solvents. The metabolic fate and the depuration rate of BaP from the two feeding groups were compared. In a second experiment, mussels were exposed to [3H]‐BaP or [14C]‐BaP either injected or via the surrounding water, and the tissue distribution of radiolabeled compound was studied. The half‐life of BaP was 15–17 days and unaffected by the food concentration. The metabolic profile differed slightly between the two treatments. Animals in the L group had a significant peak in the quantity of macromolecular adducts eight days after the injection, whereas the H group had a fairly stable amount of adducts throughout the experimental period. The tissue distribution study revealed that the radiolabeled compound was mainly present in the epithelial cells of the hepatopancreas and the ciliated epithelial cells of the gills. A fraction of the radioactivity was firmly bound.

Relationship between metabolism and bioaccumulation of benzo[α]pyrene in benthic invertebrates

“…This confirms that traditional estimates of bioavailability are affected by metabolic ability of the organisms being investigated. This supports data published previously [11,[27][28][29], demonstrating that metabolic products can represent a substantial portion of PAH body burdens in organisms that can metabolize PAHs, creating the potential for trophic transfer of PAH metabolites to consumer organisms. Also plotted in Figure 2 for comparison are mean BAF for total B[a]P-derived tissue radioactivity as a function of metabolic capability where no significant correlation was observed.…”

“…It is possible that different sizes or ages of animals, different routes of exposure, or different extraction schemes contributed to the varied results reported above for this species. This suggests that, while bivalves do seem to have limited ability to metabolize PAHs in general, there still is considerable variation from species to species and the ability of bivalves to metabolize PAH cannot be summarily ignored [28,35]. As a group, the results for B[a]P metabolism in bivalves generally are consistent with literature values, which show variable (though generally low) B[a]P metabolism ranging from 17 to 30% (Table 2).…”

“…Although a greater ability to metabolize and excrete PAHs can result in lower measured body burdens of parent compound, it also may result in higher toxicity from exposure to parent PAH due to the formation of toxic metabolites [26]. PAH metabolites that covalently bind to macromolecules also have been shown to be persistent in organism tissues and this may make them available for trophic transfer to predators of benthic organisms [11,[27][28][29]. In this way, PAH metabolism plays a dual role of ridding the organism of parent PAH through modification and eventual excretion, but also of cre- ating highly toxic metabolic intermediates that can have additional harmful effects.…”

Benzo[a]pyrene absorption and exposure pathways in the green mussel Perna viridis

“…We did not consider the metabolism of B a P in the mussels during the 1‐d depuration period but assumed that it was negligible because of the low cytochrome P450 enzyme activity [39]. Recently, Magnusson et al [40] showed that only 12 to 13% of B a P in the mussel M. edulis may be metabolized to a water‐soluble fraction (e.g., conjugated metabolites) after 32 d of depuration. If the elimination rate of B a P was relatively fast, the AE calculated by the mass balance method may have been overestimated.…”

Effect of exposure to benzo[a]pyrene on SODs, CYP1A1/1A2- and CYP2E1 immunopositive proteins in the blood clam Scapharca inaequivalvis

“…Similarly, the half-life of loss of B[a]P from S. inaequivalvis was 24 h (tissue B[a]P levels at 36 h were 50% of those at 12 h) compared to six to ten days for the clam Rangia cuneata following a one-day exposure period (Neff et al, 1976). In vivo biotransformation of B[a]P occurs in molluscs, but considerable species variation is reported (Magnusson et al, 2000;Varanasi et al, 1985).…”