Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

The glutathione-S-transferases (GSTs) are a multiclass family of enzymes that help to detoxify lipid-soluble xenobiotics by conjugating them to reduced glutathione. Studies from this laboratory have shown that changes in GST, and other antioxidant defenses, are part of the biochemical adaptation of animals to severe environmental stress. Spadefoot toads are desert-dwelling amphibians that endure severe dryness by burrowing and entering dormancy (estivation).To analyze the basis of the estivation-induced reduction in GST in toad tissues, we purified and characterized GST from liver and leg muscle of awake and dormant toads, and also from leopard frogs for comparison. Liver GST showed high variation, differing between frogs and toads as well as between awake and dormant states in toads; by contrast, muscle GST was very similar between frogs and toads. Two main isoforms of GST were purified from frog liver, whereas single, but different, GST isoforms were purified from liver of awake versus dormant toads. Kinetic analysis showed that reduced GST activity in liver during estivation was due to the change to a different GST isoform whereas estivation simply reduced GST maximal activity in muscle. Physical and kinetic characteristics indicated that most frog and toad liver and muscle GSTs could be assigned to the Mu class of GST isozymes.

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Poster Number PAgrundy0446
Keywords: dormancy, antioxidants, amphibian, isoenzymes, leopard frog