RELATIONSHIP BETWEEN ANOXIA EXPOSURE AND ANTIOXIDANT STATUS IN THE FROG RANA-PIPIENS

The biochemical adaptations of cellular antioxidant defenses that perm it anoxia-tolerant animals to deal effectively with rapid and large ch anges in oxygen availability, and hence oxidative stress, during trans itions from anoxia to normoxia provide insights into the strategies of antioxidant defense that could help to minimize reperfusion injuries to mammalian organs after anoxia/ischemia stress. The present study an alyzes the effects of 30 h anoxia exposure followed by reoxygenation o n the antioxidant defenses (activities of five enzymes, glutathione st atus) and lipid peroxidation damage to organs of the leopard frog Rana pipiens (5 degrees C-adapted autumn frogs). Exposure to 30 h anoxia r esulted in significant increases in the activities of skeletal muscle and heart catalase (by 53 and 47%), heart and brain glutathione peroxi dase (by 75 and 30%), and brain glutathione S-transferase (by 66%). In most cases, enzyme activities had returned to the control values afte r 40 h aerobic recovery. Activities of superoxide dismutase and glutat hione reductase were unaltered in all of the organs, and anoxia/recove ry had no effect on any of the enzymes in liver. Glutathione equivalen ts (GSH-eq) were maintained in four organs during anoxia but decreased by 32% in brain during anoxia. Brain GSH-eq had recovered after 90 mi n reoxygenation, and, in addition, hepatic GSH-eq rose by 71% after 90 min reoxygenation. The ratio of oxidized glutathione to GSH-eq was al so affected by anoxia in an organ-specific way. Lipid peroxidation, as sessed as the content of thiobarbituric acid-reactive substances (TBAR S), was unaltered in skeletal muscle and liver after 30 h anoxia expos ure or short (25 and 90 min)- or long-term (40 h) periods of reoxygena tion, indicating that cycles of natural and survivable anoxia/reoxygen ation occur without significant increase in TBARS in selected organs. Overall, the data demonstrate that elements of the antioxidant system of R. pipiens are induced during anoxia exposures as a possible prepar ation for dealing with potentially harmful oxygen reperfusion stress.