... Mb concentration and O 2 carrying capacity as markers of diving behavior in whales, it still remains unexplored whether whale Mbs differ in their O 2 affinities and nitrite reductase and peroxidase enzymatic activities, all functions that could contribute to differences in diving capacities...

... in turtle had a higher nitrite reductase activity than in hypoxia-intolerant species. Taken together, these data indicate constitutively high circulating levels of NO metabolites and significant increases in blood NO after anoxia and reoxygenation that may contribute to the complex physiological response...