title: Oxidative damage and antioxidants in Rana sylvatica, the freeze-tolerant wood frog.
abstract: Freeze-tolerant wood frogs (Rana sylvatica) must endure prolonged ischemia on freezing. Reperfusion on thawing brings with it the potential or oxidative damage due to reactive oxygen species formation, a well-known consequence of mammalian ischemia-reperfusion. To determine whether oxidative damage occurs during thawing and how frogs deal with this, we examined oxidative damage and antioxidant and prooxidant systems in tissues of Rana sylvatica and a nonfreezing relative, Rana pipiens. Glutathione status indicated little oxidative stress in tissues during freezing or thawing; an increase of the glutathione pool in the oxidized form was observed during freezing only in Rana sylvatica kidney (by 85%) and brain (by 33%). Oxidative damage to tissue lipids, measured as the levels of thiobarbituric acid-reactive substances and/or by an Fe(III)-xylenol orange assay, did not increase above control values pver a freeze-thaw time course. Correlative data showing increased activities of some antioxidant enzymes during freezing, notably glutathione peroxidase (increasing 1.2- to 2.5-fold), as well as constitutively higher activities of antioxidant enzymes and higher levels of glutathione in the freeze-tolerant species compared with Rana pipiens, suggest that antioxidant defenses play a key role in amphibian freeze tolerance.
authors.affiliation: Institute of Biochemistry, Carleton University, Ottawa, Ontario, Canada.
authors.forename: D R
authors.initials: DR
authors.lastname: Joanisse
authors.forename: K B
authors.initials: KB
authors.lastname: Storey
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D005260:Female; D005615:Freezing; D005978:Glutathione / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D011894:Rana pipiens / Q000502:physiology; D011898:Ranidae / Q000378:metabolism / Q000502:physiology*; D014968:Xanthine Dehydrogenase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D010088:Oxidoreductases; D014968:Xanthine Dehydrogenase; D005978:Glutathione