Microsomal estrogen metabolism in channel catfish
Harshala Butala1, Christine Metzger, John Rimoldi
1Department of Chemical Engineering, University of Mississippi, University, MS 38677-1848, USA.
Marine Environmental Research
|June 5, 2004
Summary
Benzo(a)pyrene (BaP) exposure in channel catfish (Ictalurus punctatus) increased the formation of potentially genotoxic 4-hydroxyestradiol, a metabolite of estrogen. This highlights the impact of environmental contaminants on fish P450 gene involvement in estrogen metabolism.
Area of Science:
- Environmental Toxicology
- Molecular Biology
- Fish Metabolism
Background:
- Cytochrome P450 (P450) genes play a crucial role in metabolizing environmental contaminants and endogenous compounds like estrogens.
- Estrogen metabolites, such as 4-hydroxyestradiol, can be genotoxic and potentially carcinogenic.
- Channel catfish (Ictalurus punctatus; CC) are important indicators of aquatic ecosystem health.
Purpose of the Study:
- To investigate the involvement of P450 genes in estrogen metabolism in channel catfish.
- To determine the formation of potentially carcinogenic 4-hydroxyestradiol in channel catfish exposed to environmental contaminants.
- To assess the impact of benzo(a)pyrene (BaP) on estrogen metabolism and P450 activity in channel catfish.
Main Methods:
- Assessing estradiol metabolism and ethoxyresorufin-O-deethylase (EROD) activity in various channel catfish tissues.
- Analyzing fish from contaminated sites, laboratory controls, and BaP-exposed fish.
- Utilizing gas chromatography/mass spectrometry (GC/MS) to identify and quantify estrogen metabolites.
Main Results:
- Benzo(a)pyrene (BaP) induced liver and gill EROD activity, but not significantly in fish from contaminated sites.
- The predominant estrogen metabolites in channel catfish liver, gill, and gonad microsomes were 2-hydroxyestradiol and estrone.
- BaP-treatment increased the ratio of 4-hydroxyestradiol to 2-hydroxyestradiol in liver microsomes, indicating enhanced formation of the potentially genotoxic metabolite.
Conclusions:
- BaP exposure influences estrogen metabolism in channel catfish, specifically increasing the formation of 4-hydroxyestradiol.
- Fish P450 genes involved in estrogen metabolism may be susceptible to environmental contamination.
- Further research is needed to identify specific P450 genes involved in estrogen genotoxicity in aquatic organisms.
