The release of reactive oxygen species has been described in hypothermic cells and tissues. Fructose 1,6-biphosphate (F1,6-BP) Protects tissue stored at cold temperatures. We study the effect of F1,6-BP in vivo administration on anaesthetized rats exposed to cold stress (4 degrees C chamber for 30 min) and rewarming, to see if it alters cold-induced oxidative injury. Body temperatures show that the animals reached moderate hypothermia (26.80 +/- 0.62 degrees C) after 30 min of cold exposition. A decrease in mean arterial pressure was found. One group of animals was then rewarmed. Both hypothermia and rewarming increased the production of thiobarbituric acid-reactive substances, an index of lipid peroxidation, and reduced the antioxidant levels of plasmatic sulfhydryl groups, as well as decreasing the enzymatic activities of Cu,Zn-superoxide dismutase (Cu,Zn-SOD), catalase and GSH peroxidase in erythrocytes. Administration of F1,6-BP increased sulfhydryl groups and limited lipid peroxidation in plasma. It furthermore enhanced Cu,Zn-SOD and GSH peroxidase antioxidant activity in erythrocytes and preserved mean arterial pressure. Therefore, F1,6-BP has therapeutic potential based on its ability to reduce free-radical injury resulting from acute cold exposure and rewarming in vivo. (c) 2008 Elsevier B.V. All rights reserved.