beta-Naphthoflavone-inducible cytochrome P4501A1 activity in liver microsomes of the marine safi fish (Siganus canaliculatus)

Hepatic metabolism of contaminants in the terapontid fish, yellowtail trumpeter (Amniataba caudavittata Richardson)

The yellowtail trumpeter (Amniataba caudavittata) is an estuarine-dependent omnivorous fish found in the Swan-Canning Estuary, Western Australia. Thirty five fish were injected with either the polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P), the synthetic flavenoid beta-naphthoflavone (BNF), or used as controls. The fish were then sampled at 3 and 7 days postinjection. Induction of the enzyme ethoxyresorufin O-deethylase (EROD) activity was nonsignificant while ethoxycoumarin O-deethylase (ECOD) activity induction differed amongst treatments. A high interindividual variability in the EROD activity was observed. The measurement of sorbitol dehydrogenase in the serum (s-SDH) was elevated (BNF 2.2 times and B[a]P 3.2 times the control fish) demonstrating that liver cell damage had occurred. Increases in biliary metabolites of both B[a]P-type and pyrene-type (19 times and 3.4 times the controls respectively) indicated that detoxification of pyrene-type compounds had taken place. Fish of the Terapontidae family, such as the yellowtail trumpeter, were found to be suitable for biomonitoring the health of the Swan-Canning Estuary. A combination of ECOD activity, s-SDH, and the measurement of biliary metabolites represents a suitable suite of biomarkers for environmental monitoring of the sublethal effects of PAH pollution in these fish.

Earthworm cytochrome P450 determination and application as a biomarker for diagnosing PAH exposure

We developed a new microsome purification method and used the Omura and Sato method to measure the total content of cytochrome (Cyt) P450 in earthworm (Eisenia fetida) microsomes. In method development, two different pretreatments, i.e. solubilization or manual separation were used to purify worm microsomes. Solubilization was more effective than manual separation and difference spectra showed a peak at 450 +/- 1 nm in microsomes received solubilization pretreatment. We conducted a 48 h contact test by exposing worms on pyrene (Py) and benzo[a]pyrene (BaP) spiked filter paper. A dose-response relationship was established between total P450 content and the concentration of Py or BaP ranging from 10(-6) mg mL(-1) to 10(-2) mg mL(-1). Results show that total Cyt P450 content in earthworms is a promising biomarker for diagnosing PAHs exposure at sublethal dose ranges.

Fish bioaccumulation and biomarkers in environmental risk assessment: a review

In this review, a wide array of bioaccumulation markers and biomarkers, used to demonstrate exposure to and effects of environmental contaminants, has been discussed in relation to their feasibility in environmental risk assessment (ERA). Fish bioaccumulation markers may be applied in order to elucidate the aquatic behavior of environmental contaminants, as bioconcentrators to identify certain substances with low water levels and to assess exposure of aquatic organisms. Since it is virtually impossible to predict the fate of xenobiotic substances with simple partitioning models, the complexity of bioaccumulation should be considered, including toxicokinetics, metabolism, biota-sediment accumulation factors (BSAFs), organ-specific bioaccumulation and bound residues. Since it remains hard to accurately predict bioaccumulation in fish, even with highly sophisticated models, analyses of tissue levels are required. The most promising fish bioaccumulation markers are body burdens of persistent organic pollutants, like PCBs and DDTs. Since PCDD and PCDF levels in fish tissues are very low as compared with the sediment levels, their value as bioaccumulation markers remains questionable. Easily biodegradable compounds, such as PAHs and chlorinated phenols, do not tend to accumulate in fish tissues in quantities that reflect the exposure. Semipermeable membrane devices (SPMDs) have been successfully used to mimic bioaccumulation of hydrophobic organic substances in aquatic organisms. In order to assess exposure to or effects of environmental pollutants on aquatic ecosystems, the following suite of fish biomarkers may be examined: biotransformation enzymes (phase I and II), oxidative stress parameters, biotransformation products, stress proteins, metallothioneins (MTs), MXR proteins, hematological parameters, immunological parameters, reproductive and endocrine parameters, genotoxic parameters, neuromuscular parameters, physiological, histological and morphological parameters. All fish biomarkers are evaluated for their potential use in ERA programs, based upon six criteria that have been proposed in the present paper. This evaluation demonstrates that phase I enzymes (e.g. hepatic EROD and CYP1A), biotransformation products (e.g. biliary PAH metabolites), reproductive parameters (e.g. plasma VTG) and genotoxic parameters (e.g. hepatic DNA adducts) are currently the most valuable fish biomarkers for ERA. The use of biomonitoring methods in the control strategies for chemical pollution has several advantages over chemical monitoring. Many of the biological measurements form the only way of integrating effects on a large number of individual and interactive processes in aquatic organisms. Moreover, biological and biochemical effects may link the bioavailability of the compounds of interest with their concentration at target organs and intrinsic toxicity. The limitations of biomonitoring, such as confounding factors that are not related to pollution, should be carefully considered when interpreting biomarker data. Based upon this overview there is little doubt that measurements of bioaccumulation and biomarker responses in fish from contaminated sites offer great promises for providing information that can contribute to environmental monitoring programs designed for various aspects of ERA.

Ethoxyresorufin-O-deethylase (EROD) activity in fish as a biomarker of chemical exposure

This review compiles and evaluates existing scientific information on the use, limitations, and procedural considerations for EROD activity (a catalytic measurement of cytochrome P4501A induction) as a biomarker in fish. A multitude of chemicals induce EROD activity in a variety of fish species, the most potent inducers being structural analogs of 2,3,7,8-tetracholordibenzo-p-dioxin. Although certain chemicals may inhibit EROD induction/activity, this interference is generally not a drawback to the use of EROD induction as a biomarker. The various methods of EROD analysis currently in use yield comparable results, particularly when data are expressed as relative rates of EROD activity. EROD induction in fish is well characterized, the most important modifying factors being fish species, reproductive status and age, all of which can be controlled through proper study design. Good candidate species for biomonitoring should have a wide range between basal and induced EROD activity (e.g., common carp, channel catfish, and mummichog). EROD activity has proven value as a biomarker in a number of field investigations of bleached kraft mill and industrial effluents, contaminated sediments, and chemical spills. Research on mechanisms of CYP1A-induced toxicity suggests that EROD activity may not only indicate chemical exposure, but also may also precede effects at various levels of biological organization. A current research need is the development of chemical exposure-response relationships for EROD activity in fish. In addition, routine reporting in the literature of EROD activity in standard positive and negative control material will enhance confidence in comparing results from different studies using this biomarker.

Effect of bitter melon (Momordica charantia) fruit juice on the hepatic cytochrome P450-dependent monooxygenases and glutathione S-transferases in streptozotocin-induced diabetic rats

Bitter melon (Momordica charantia), commonly known as karela, has been reported to have hypoglycemic, antiviral, antidiabetic, and antitumor activities. In the present study, we have investigated the effects of oral feeding of karela fruit juice on the hepatic cytochrome P450 (CYP) and glutathione S-transferase (GST) drug-metabolizing enzymes in the streptozotocin (STZ)-induced diabetic rat. Hepatic CYP contents, ethoxycoumarin-O-deethylase (ECOD), ethoxyresorufin-O-deethylase (EROD), aniline hydroxylase (AH), and aminopyrene N-demethylase (APD) activities were measured in control, diabetic, and karela juice fed animals. Diabetic rats exhibited a 50-100% increase in AH and EROD activities that was reversed by karela juice feeding. In addition, a decrease (17-20%) in the activities of APD and ECOD was observed in diabetic rat liver. Feeding of karela juice to the diabetic animals brought the level of APD close to that of control animals, while ECOD was further reduced to 60% of the control value. The cytosolic glutathione concentration was decreased in diabetic rats, and karela juice feeding normalized the effect. However, an increase (of 20-30%) in the GST activity was observed in both diabetic and karela juice fed rats. Western immunoblot analysis of CYP and GST isozymes exhibited a differential response during diabetes. The expression of CYP1A1, 2B1, 2E1, 3A4, and 4A2 in diabetes, while a decrease in GST mu was observed. Our results suggest that the changes in hepatic phase I and phase II drug-metabolizing enzyme activities in the STZ-induced diabetic animals may be associated with the altered expression of different CYP and GST isozymes. In addition, we have also observed that karela does not always reverse the effects on drug-metabolizing enzymes in STZ-induced diabetes.