Diving seals: are they a model for coping with oxidative stress?

Area of Science:

• Marine Mammal Physiology
• Comparative Physiology
• Oxidative Stress Biology

Background:

• Seals' diving requires cardiovascular adjustments, leading to organ vasoconstriction and subsequent reperfusion.
• Reperfusion after dives can cause oxidative stress due to reactive oxygen species (ROS) production.
• Understanding seal adaptations to oxidative insult is crucial for marine mammal physiology.

Purpose of the Study:

• To investigate adaptive mechanisms in ringed seal (Phoca hispida) tissues against oxidative stress from repeated ischemia-reperfusion cycles.
• To compare the oxidative stress response of ringed seal tissues with those of pigs.

Main Methods:

• Ringed seal heart, muscle, and kidney tissues were obtained and subjected to oxidative stress using xanthine oxidase in vitro.
• Quantification of superoxide radical (O(2)(.-)) production, lipid peroxidation (TBARS), and antioxidant capacity (AOX) via spectrophotometry.
• Comparison with similarly treated pig tissues to assess species-specific differences in oxidative tolerance.

Main Results:

• Ringed seal tissues, contrary to expectations, showed higher O(2)(.-) and TBARS levels compared to pig tissues when subjected to oxidative stress.
• In vitro studies demonstrated that ringed seal tissues can be induced to generate ROS.
• Ringed seal tissues exhibited significantly higher antioxidant capacity (AOX) than pig tissues.

Conclusions:

• Ringed seal tissues possess inherent tolerance to oxidative stress, potentially linked to ROS production or enhanced scavenging.
• The findings suggest that seals may utilize ROS production, akin to preconditioning, or superior antioxidant defenses for protection during diving.
• These adaptations are vital for the survival of seals in their challenging diving environment.