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Differential expression of two CYP1A genes in rainbow trout (Oncorhynchys mykiss)

C M Råbergh1, N H Vrolijk, M M Lipsky

  • 1Department of Pathology, Program in Toxicology, University of Maryland at Baltimore, 10 South Pine Street, Baltimore, Maryland 21201, USA. christina.rabergh@utu.fi

Toxicology and Applied Pharmacology
|June 22, 2000
PubMed

Insights

Rainbow trout exhibit differential gene expression in CYP1A3 and CYP1A1 in response to chemical inducers like beta-naphthoflavone and 3-methylcholanthrene. This study clarifies their distinct responses in vivo and in vitro, aiding toxicological research.

Area of Science:

  • Environmental Toxicology
  • Molecular Biology
  • Biochemistry

Background:

  • Cytochrome P450 (CYP) enzymes play a crucial role in xenobiotic metabolism.
  • Rainbow trout (Oncorhynchus mykiss) possess multiple CYP1A genes with potentially differential responses to environmental contaminants.
  • Previous nomenclature for trout CYP1A genes has been revised, with CYP1A3 and CYP1A1 being the current designations.

Purpose of the Study:

  • To investigate the differential expression of two rainbow trout CYP1A genes (CYP1A3 and CYP1A1) in response to known CYP1A inducers.
  • To compare the in vivo and in vitro responses of these genes to various chemical treatments.
  • To clarify the nature of a previously described trout CYP1A cDNA sequence.

Main Methods:

  • Quantitative analysis of CYP1A3 and CYP1A1 mRNA levels using RNase protection assay.
  • Treatment of rainbow trout with inducers beta-naphthoflavone (BNF) and 3-methylcholanthrene (3-MC) in vivo.
  • Treatment of primary hepatocyte cultures with BNF, 3-MC, isosafrole (ISF), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vitro.
  • Sequence analysis and comparison of trout CYP1A genes and cDNA clones.

Main Results:

  • Significant, inducer-dependent induction of both CYP1A3 and CYP1A1 mRNA was observed in vivo.
  • BNF and 3-MC showed differential induction patterns for CYP1A3 and CYP1A1 mRNA in vivo.
  • In vitro, all tested inducers (BNF, 3-MC, ISF, TCDD) significantly induced both genes, but with less pronounced differential responses compared to in vivo.
  • Reanalysis revealed the Heilmann et al. cDNA is a hybrid of trout CYP1A3 and CYP1A1 genes.

Conclusions:

  • Rainbow trout CYP1A3 and CYP1A1 genes exhibit differential, inducer-dependent expression patterns.
  • The in vivo response to CYP1A inducers is more distinct between the two genes than the in vitro response.
  • The findings contribute to a better understanding of fish toxicology and gene regulation by xenobiotics.

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