GLUTATHIONE SYSTEMS AND ANOXIA TOLERANCE IN TURTLES

Effects of anoxic submergence (20 h at 5 degrees C) and subsequent 24 h aerobic recovery on glutathione levels and the activities of glutath ione-related enzymes were examined in six tissues of Trachemys scripta elegans. Anoxia exposure resulted in tissue-specific changes in enzym e maximal activities, the most dramatic being suppression of gammaglut amyl transpeptidase (gamma-GTPase) activity in anoxic kidney to only 2 % of control. Anoxia exposure also caused significant decreases in act ivities of liver and heart glutathione-S-transferase (GST) (by 25 and 42%), heart glutathione reductase (GR) (by 67%), liver gamma-GTPase (b y 71%), and red muscle glutaredoxin (GRN) (by 56%). By contrast, anoxi a exposure increased the activities of GR in liver and red muscle (by 52 and 80%), glutathione synthetase (GS) in white muscle (by 300%), an d GRN in white muscle (by 400%). During aerobic recovery after anoxia, GST activity decreased in red muscle, kidney, and brain (by 72, 56, a nd 39%); GR decreased in liver and red muscle (by 52 and 80%); and GRN fell in red muscle (by 56%). Other activities rose during recovery: G R in heart (by 64%), GS in heart and brain (by 200%), and gamma-GTPase in brain (by 63%). Tissue pools of total glutathione were high in com parison with other ectotherms. Levels decreased during anoxia in four organs to 49-67% of control values. During aerobic recovery the reduce d glutathione-to-oxidized glutathione ratio (GSH/GSSG) increased in he art, kidney, and brain, indicating that oxidative stress did not occur in these organs. Rather than maintaining high levels of glutathione i n tissues to prevent oxidative stress during aerobic recovery, turtles sustain high GSW/GSSG by regulating the activities of glutathione-usi ng enzymes.