Hypoxia tolerance, nitric oxide, and nitrite: lessons from extreme animals

Area of Science:

• Physiology
• Biochemistry
• Zoology

Background:

• Vertebrates exhibit varying tolerance to oxygen deprivation (hypoxia).
• Extreme hypoxia survival is exemplified by turtles and crucian carp, enduring months without oxygen.
• Key survival mechanisms include metabolic depression, oxidative damage protection, and blood flow redistribution.

Purpose of the Study:

• To review recent findings on the role of nitric oxide (NO) and nitrite in vertebrate hypoxia tolerance.
• To highlight the significance of NO and nitrite signaling in adaptive responses to extreme oxygen deprivation.

Main Methods:

• Literature review of recent research on NO and nitrite in hypoxia tolerance.
• Focus on studies involving red-eared slider turtles, crucian carp, and marine mammals.

Main Results:

• Nitric oxide (NO) and its metabolite nitrite are central regulators of hypoxia survival responses.
• These signaling molecules are vital for metabolic depression, antioxidant defense, and circulatory adjustments.
• Evidence spans air-breathing turtles, fish, and diving marine mammals.

Conclusions:

• Nitric oxide (NO) and nitrite signaling play a widespread and critical role in vertebrate adaptation to extreme hypoxia.
• Understanding these pathways offers insights into physiological resilience during oxygen scarcity.