Hepatic ethoxyresorufin‐<i>O</i>‐deethylase activity and inducibility in wild populations of double‐crested cormorants (<i>Phalacrocorax auritus</i>)

Davis, Jay A; Fry, D. Michael; Wilson, Barry W.

doi:10.1002/etc.5620160717

Cited by 14 publications

(17 citation statements)

References 43 publications

(50 reference statements)

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“…The present study and others (Davis et al ; Sanderson et al ; Smart and Daly ) suggest that expression and induction of CYP1A enzymes can be extremely variable in cultured cells prepared from individuals. We report that basal mRNA expression varied by 20‐fold for CYP1A4 and by 126‐fold for CYP1A5 among 55 hepatocyte cultures prepared from individual herring gulls (Table ).…”

Section: Discussionsupporting

confidence: 55%

“…Several lines of evidence suggest that although experimental error may contribute to variation in CYP1A mRNA expression between individual hepatocyte preparations, it is unlikely to be its main cause. Davis et al () observed a good correlation between EROD activity measured in whole‐liver tissue and DMSO‐treated hepatocytes cultured from the same individual. Sanderson et al () observed that variation in EROD EC50 was considerably lower among hepatocyte cultures prepared from pools of 2 or 3 livers than among hepatocyte cultures prepared from individuals.…”

Section: Discussionmentioning

confidence: 97%

“…As in other studies, a proportion of hepatocyte preparations from each population did not produce a CYP1A response on exposure to test compounds. Davis et al () report that 18% of hepatocyte cultures prepared from individual double‐crested cormorants did not appreciably induce EROD activity in response to ß‐naphthoflavone. Sanderson et al () observed that the proportion of nonresponsive hepatocyte cultures prepared from individual embryos of 4 avian species ranged from 8 to 17%.…”

Section: Discussionmentioning

confidence: 99%

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Interindividual variation in the cytochrome P4501A response to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in herring gull embryo hepatocytes

Head

Kennedy

2019

Enviro Toxic and Chemistry

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Exposure to dioxin‐like compounds is consistently associated with concentration‐dependent induction of cytochrome P4501A (CYP1A) enzymes in primary cultures of avian hepatocytes. We have previously demonstrated that the median effective concentration (EC50) for induction of this response is predictive of in vivo sensitivity to dioxin‐like compounds in birds. We investigated sources of interindividual variation in the CYP1A response to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) in wild herring gulls and considered how this variation may complicate dioxin sensitivity estimates based on the CYP1A bioassay. Concentration‐dependent effects of TCDD on CYP1A mRNA expression were characterized in 55 hepatocyte cultures prepared from individual herring gull embryos. A large degree of variability was observed among the hepatocyte culture preparations. For example, 1) basal CYP1A4 and CYP1A5 mRNA expression varied by 20‐ and 126‐fold, respectively, among individuals, and 2) exposure to TCDD induced CYP1A4 mRNA expression by 57‐fold in the most responsive sample but did not significantly induce CYP1A4 mRNA expression above baseline values in 42% of hepatocyte culture preparations. Environmental and genetic factors contributing to the observed variability are discussed. Despite the large amount of interindividual variation, we conclude that reproducible EC50‐based estimates of species sensitivity can be obtained from the CYP1A cell culture bioassay when samples are collected from relatively uncontaminated colonies. Environ Toxicol Chem 2019;38:660–670. © 2019 SETAC

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Section: Discussionsupporting

confidence: 55%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

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Interindividual variation in the cytochrome P4501A response to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in herring gull embryo hepatocytes

Head

Kennedy

2019

Enviro Toxic and Chemistry

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“…One major difference between the present study and those reported previously is that concentration‐response experiments were performed in hepatocyte preparations derived from individual livers (with the exception of the Forster's tern), whereas other studies have generally used pooled samples. An exception is a recent study that examined the response of hepatocytes from individual 17‐d‐old double‐crested cormorant embryos to β‐naphthoflavone (BNF) [32]. In our study, TCDD concentration‐response curves for EROD and porphyrin induction were generated in every hepatocyte preparation as positive controls, as well as several HAHs, depending on the amount of material available.…”

Section: Discussionmentioning

confidence: 99%

In vitro induction of ethoxyresorufin‐O‐deethylase and porphyrins by halogenated aromatic hydrocarbons in avian primary hepatocytes

Sanderson

Kennedy

Giesy

1998

Enviro Toxic and Chemistry

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Ethoxyresorufin‐O‐deethylase (EROD) and porphyrin induction responses of primary hepatocytes to halogenated aromatic hydrocarbons (HAHs) were examined in newly hatched domestic chickens, herring gulls, ring‐billed gulls, double‐crested cormorants, and Forster's terns. Concentration–response relationships were determined for both biochemical responses in hepatocyte preparations derived from individual avian livers (except for the tern). The choice of vehicle used to dose chicken hepatocytes greatly affected the potencies and efficacies of HAHs. Dimethyl sulfoxide resulted in median effective concentration (EC50) values for EROD induction that were between 10 and 15 times less than isooctane (isooctane was used throughout the study). Neither vehicle induced EROD activity by itself. Concentration‐dependent increases in EROD activity were observed with several HAHs, and their potencies (EC50 values) were compared to that of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) within each hepatocyte preparation to determine relative potency factors (RPFs). Differences in sensitivity to these responses were observed among individuals within each of the species and among species. Median EC50 values (nM) for EROD induction by TCDD were 0.72, 13, 20, 25, and 150 for the chicken, cormorant, ring‐billed gull, herring gull, and tern hatchling, respectively. Relative potency factors for several HAHs were different, in both ranking and potency, from those generally derived in mammalian hepatocytes. Porphyrin accumulation was observed occasionally with the most potent aryl hydrocarbon receptor agonists, but most HAHs were not tested at concentrations sufficiently high to observe a consistent response. This study provides information on interindividual and interspecies differences in responsiveness to TCDD‐like compounds and provides species‐specific RPFs that may prove useful for the purpose of hazard and risk assessment for fish‐eating birds.

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“…EROD activity is a useful biomarker for detecting early signs of contamination [3], [19], [20], [10], [21]. Understanding the innate differences in species-specific detoxification abilities is important for recognizing the species that are at greatest risk in polluted environments [4].…”

Section: Introductionmentioning

confidence: 99%

Variation of Basal EROD Activities in Ten Passerine Bird Species – Relationships with Diet and Migration Status

et al. 2012

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Inter-specific differences in animal defence mechanisms against toxic substances are currently poorly understood. The ethoxyresorufin-O-deethylase (EROD) enzyme plays an important role in defence against toxic chemicals in a wide variety of animals, and it is an important biomarker for environmental contamination. We compared basal hepatic EROD activity levels among ten passerine species to see if there is inter-specific variation in enzyme activity, especially in relation to their diet and migration status. Migratory insectivores showed higher EROD activity compared to granivores. We hypothesize that the variable invertebrate diet of migratory insectivores contains a wider range of natural toxins than the narrower diet of granivores. This may have affected the evolution of mixed function oxidases (MFO) system and enzyme activities. We further tested whether metabolic rates or relative liver size were associated with the variation in detoxification capacity. We found no association between EROD activity and relative (per mass unit) basal metabolic rate (BMR). Instead, EROD activity and relative liver mass (% of body mass) correlated positively, suggesting that a proportionally large liver also functions efficiently. Our results suggest that granivores and non-migratory birds may be more vulnerable to environmental contaminants than insectivores and migratory birds. The diet and migration status, however, are phylogenetically strongly connected to each other, and their roles cannot be fully separated in our analysis with only ten passerine species.

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Hepatic ethoxyresorufin‐O‐deethylase activity and inducibility in wild populations of double‐crested cormorants (Phalacrocorax auritus)

Cited by 14 publications

References 43 publications

Interindividual variation in the cytochrome P4501A response to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in herring gull embryo hepatocytes

Interindividual variation in the cytochrome P4501A response to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in herring gull embryo hepatocytes

In vitro induction of ethoxyresorufin‐O‐deethylase and porphyrins by halogenated aromatic hydrocarbons in avian primary hepatocytes

Variation of Basal EROD Activities in Ten Passerine Bird Species – Relationships with Diet and Migration Status

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