Use of mixed‐function oxygenases to monitor contaminant exposure in wildlife

Abstract

This overview examines the utility of mixed‐function oxygenase (MFO) enzymes as a bio‐effects monitor for wildlife (amphibians, reptiles, birds and mammals) in view of their widespread use as indicators of contaminant exposure in aquatic invertebrates and fish. Phylogenetic trends in MFO activity, toxicological implications of induction and the relationship between contaminant exposure and MFO activity are discussed. Field studies using avian embryos and hatchlings suggest that MFO induction has utility for documenting contaminant exposure; however, findings in adult birds and mammals are equivocal. Age, sex and season are sources of variation that require consideration when undertaking field trials. Further understanding of MFO inducibility among species and application of recently developed analytical techniques including quantification of specific cytochrome P‐450 isozymes are warranted.

Environmental polychlorinated biphenyl exposure and cytochromes P450 in raccoons (Procyon lotor)

“…In addition, there was a significant positive relationship between PROD activity and CYP1A1 and between BROD activity and CYP1A1. Additionally, other factors, including age, sex, reproductive condition, and season, can affect CYP induction [6]. In an earlier study, Letcher et al [3] determined that EROD and PROD, but not BROD, correlated with the CYP1A subfamily from polar bear samples.…”

“…A number of environmental and biological factors can interfere with the measurement of catalytic activity using different substrates in spectrophotometric assays [6]. Catalytic assays such as EROD showed a greater range of response than the immunoblot assay.…”

“…Exposure to PCBs has been shown to result in a number of physiological and biochemical alterations in wildlife, including induced hepatic microsomal enzyme activity [1][2][3][4][5][6][7][8], altered endocrine function, reduced reproduction [9,10], and altered immune function [11][12][13][14]. Polychlorinated biphenyls resist thermal, mechanical, and biological breakdown and readily bioaccumulate and biomagnify in exposed organisms due to their lipophilic nature.…”

“…Therefore, more direct methods of measuring liver enzyme induction may be more accurate and reliable [6]. that respond to specific chemical classes or congeners.…”

The role of biomarkers in the health assessment of aquatic ecosystems

“…The role of constitutive CYP1A based enzyme activity is a puzzle that still seeks a solution. MFO activities in fish that have been exposed in situ are ideal for the monitoring of aquatic systems where they can help to delimit the zones of influence of point sources of pollution (Rattner et al, 1989). Mixed function oxidases (which are part of the Phase 1 detoxification pathway) oxidize Ah receptor ligands rendering them vulnerable to further enzymatic or chemical reactions.…”