TP5 Mechanisms of Toxic Action
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() A novel fish glutathione S-transferase gene that protects against oxidative injury.

Gallagher, E1, Pham, R2, Hughes, E2, 1 University of Washington, Seattle, Washington, USA2 University of Florida, Gainesville, Florida, USA

ABSTRACT- Oxidative injury is a major mechanism of cell injury to mammalian and aquatic species exposed to environmental chemicals. Accordingly, the presence and expression level of detoxification gene products that remove toxic intermediates or reactive breakdown products involved in oxidative injury can be a key determinant of susceptibility to chemical toxicity. We have previously shown that largemouth bass (Micropterus salmoides), a higher order predatory freshwater fish, has a remarkable ability to conjugate 4-hydroxy-2-nonenal (4HNE), a mutagenic and cytotoxic unsaturated aldehyde produced during the peroxidation of lipids. This ability of bass to detoxify 4HNE can be traced to a glutathione S-transferase gene (bass GSTA) whose protein product has a high efficiency towards catalyzing 4HNE conjugation with the tripeptide glutathione. Genomic analysis of GSTA indicates that this gene is part of a GST gene cluster in bass. Analysis of the promoter of GSTA revealed the presence of several cis-acting regulatory elements that confer modulation of GSTA mRNA expression by several distinct classes of environmental chemicals. However, QPCR analysis of bass exposed to prototypical enzyme inducers suggests that GSTA may function more as a housekeeping gene to protect against oxidative stress. A BLAST search of the GenBank database revealed that GSTA is present in several phylogenetically diverse aquatic species, and suggesting a conservation of function via protecting certain species against the deleterious effects of peroxidative injury. The results of this project underscore the importance of identifying particular GST isoforms, as opposed to measuring overall GST activities, in assessing the role of GST in protecting against chemical injury in wild fish. Supported by NIH P42-ES07375.

Key words: largemouth bass, glutathione s-transferase, gene expression, oxidative injury

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