DIVING SEALS, ISCHEMIA-REPERFUSION AND OXYGEN RADICALS

The cardiovascular adaptations of seals that contribute to their abili ty to tolerate long periods of diving asphyxial hypoxia result in epis odic regional ischemia during diving and abrupt reperfusion upon termi nation of the dive. These conditions might be expected to result in pr oduction of oxygen-derived free radicals and other forms of highly rea ctive oxygen species. Seal organs vary during dives with respect to th e degree and persistence of ischemia. Myocardial perfusion is reduced and intermittent; kidney circulation is vigorously vasoconstricted. He art and kidney tissues from ringed seals (Phoca hispida) and domestic pigs (Sus scrofa) were compared in reactions to experimental ischemia. Resulting production of hypoxanthine, indicative of ATP degradation, was higher in pig than in seal tissues. Activity of superoxide dismuta se (SOD), an oxygen radical scavenger, was higher in seal heart. We su ggest that these results indicate enhanced protective cellular mechani sms in seals against the potential hazard of highly reactive oxygen fo rms. SOD activity was unexpectedly higher in pig kidney. (C) 1998 Else vier Science Inc. All rights reserved.