Susceptibility to oxidative stress in Adelie and emperor penguin

The antioxidant defences in aerobic organisms represent the detoxification pathway against toxicity of reactive oxygen species (ROS). These highly rea ctive molecules are normally produced during the 4-electrons reduction of m olecular oxygen to water coupled with oxidative phosphorylation, and during the activity of several enzymatic systems which produce ROS as intermediat es. However, the endogenous generation of oxyradicals may be influenced by different environmental and biological factors, and the basal efficiency of antioxidant systems generally reflects the normal prooxidant pressure to w hich organisms are exposed. If the antioxidant capacity is exceeded (i.e. a s a consequence of enhanced intracellular formation of ROS), a pathological condition, generally termed oxidative stress, may arise. In this prelimina ry work, susceptibility to oxidative stress has been compared in plasma of Adi lie penguin (Pygoscelis adeliae), emperor penguin (Aptenodytes forsteri ), south polar skua (Catharacta maccormicki) and snow petrel (Pagodroma niv ea). Within the framework of the Italian Research Program in Antarctica, bl ood samples were collected during the austral summer 1998-1999 and the Tota l Oxyradical Scavenging Capacity (TOSC) analysed. The TOSC assay, measuring the capability of biological samples to neutralise different oxyradicals, has been recently standardised to provide a quantifiable value of biologica l resistance to toxicity of ROS. Penguins exhibited higher scavenging capac ity towards peroxyl radicals than south polar skua and snow petrel. The gre ater resistance to toxicity of oxyradicals might suggest that penguins are naturally exposed to a higher basal prooxidant pressure in comparison to ot her analysed Antarctic birds.