Page 715 - The Toxicology of Fishes

Biomarkers 695

NADPH NADP +
Glutathione Reductase

Oxidized glutathione (GSSG) 2-Glutathione (GSH)
•OH

Glutathione Peroxidase Fe 2+

Oxidation of Lipids/DNA/Proteins
Catalase
O
H 2
H O 2
2
SOD
NADPH
O 2 – Xenobiotic

NADP +
O Oxyradical
2
metabolite
FIGURE 16.4 Pathways for generation and detoxification of reactive oxygen species within cells.

CYP1A in female English sole from Puget Sound that had inhibited ovarian development. In Atlantic
flounder caged in contaminated waterways in Norway, a direct correlation was observed between FACs,
CYP1A, and serum aspartate aminotransferase, indicating liver damage (Beyer et al., 1996). However,
in several fish species from Prince William Sound in Alaska following the Exxon Valdez oil spill, no
correlation was observed between DNA adducts and FACs, although positive relationships were observed
with CYP1A expression (Collier et al., 1996). In fact, in studies with juvenile turbot that were exposed
continuously for 15 days to 2 mg/L of crude oil, FACs proved to be a more sensitive indicator of PAH
exposure than CYP1A activity (Borseth et al., 1997). One of the few limiting factors in carrying out
FAC analyses is the size of the animal, as it is preferable to be able to access the bile easily from captured
or sampled fish. It should also be noted that values should be expressed as raw concentrations in animals
of similar size. If species or site comparisons utilize animals of differing size, then it has been suggested
that values be normalized to biliverdin concentrations in the bile (Richardson et al., 2004). Analysis of
these metabolites is possibly one of the most specific indicators for exposure to aromatic hydrocarbons.

Porphyrins
Porphyrins are degradation products of heme catabolism that provide oxyradical scavenging capacity
(Figure 16.4). In contrast with other studies with birds and mammals where the measurement of
porphyrins has been shown to correlate with exposure to chlorinated hydrocarbons, few studies have
been performed in fish (Melancon et al., 1992). Carboxylated porphyrin profiles have been proposed as
a biochemical indicator in lake whitefish (Coregonus clupeaformis) exposed to bleached kraft pulp mill
effluent (Xu et al., 1994). In one other study, uroporphyrinogen decarboxylase of pike (Esox lucius)
collected from a site of the Rhine River heavily contaminated with aromatic organohalogen compounds
was lower than in pike from the river Lahn, which did not have elevated organohalogen levels (Kloss,
1986). In addition to inhibitory effects on uroporphyrinogen decarboxylase, in vitro studies using fish
hepatoma cell lines have demonstrated that halogenated aromatic compounds may also disrupt porphyrin