Response of tomcod to mixtures of contaminants

Industrial and municipal waterbodies are almost always polluted with complex mixtures of contam inants, yet little is known of their toxic interactions. Studies investigated the effects of coexposure to metals (As, Cd, Cr, and Ni) and PCB77 or B[a]P on CYP1A1 inducibility and early life-stage toxicities in tomcod. In adult tomcod, all four metals significantly decreased induction of hepatic CYP1A1 by PCB77 or B[a]P, suggesting that environmental mixtures containing metals may alter toxic responses mediated through the AHR. Studies also demonstrated that PCB77 and B[a]P evoked similar AHR-mediated early life stage toxicities in tomcod (embryo mortality, accelerated time to hatching, pericardial and yolk sac edema, cranial malformations) as previously seen in TCDD or coplanar PCB-treated freshwater fish (Fig. 30.3). Coexposure of tomcod embryos to B[a]P and Cr (and to a lesser extent As) ameliorated two of these toxicities: embryo mortality and reduced time to hatching. Similarly,

Hepatic PCBs/PCDD/Fs . Bile metabolites of PAHs

Induced CYP1A1

Hepatic DNA adducts \

Ras oncogene activation %

Tumors and preneoplastic lesions Truncated age structure

Reduced population size Resistance

Trophic transfer

Ecological relevance

Figure 30.4. Schematic of biomarkers at different hierarchical levels of biological organization from exposure through the community level that are altered in Atlantic tomcod from the Hudson River.

tomcod embryos coexposed to Cr and B[a]P exhibited significantly lower levels of DNA adducts than embryos exposed to B[a]P alone (Sorrentino et al., 2004). These results suggest that coexposures to environmental mixtures result in significantly different toxicities than predicted based on experiments with single chemicals.

0 0

Post a comment