Cardiovascular function in large to small hibernators: bears to ground squirrels.

Area of Science:

• Comparative physiology
• Cardiovascular research
• Hibernation biology

Background:

• Mammalian hibernation presents diverse physiological adaptations.
• Ground squirrels and bears exhibit contrasting hibernation phenotypes and cardiac responses.

Purpose of the Study:

• To compare cardiac function and plasticity in hibernating ground squirrels and bears.
• To elucidate molecular mechanisms underlying species-specific cardiac adaptations during hibernation.

Main Methods:

• Comparative analysis of cardiac structure and function across seasons in ground squirrels and bears.
• Investigation of molecular pathways related to cardiac muscle plasticity, including sarcomeric protein modifications.

Main Results:

• Ground squirrels show increased cardiac muscle mass and decreased ventricular stiffness, with enhanced diastolic and stroke volumes during hibernation.
• Bears exhibit decreased cardiac muscle mass and increased ventricular stiffness, with no change in ventricular filling volumes.
• Both species significantly reduce cardiac output, but through different mechanisms.

Conclusions:

• Species-specific hibernation strategies lead to divergent cardiac phenotypes.
• Molecular adaptations in sarcomeric proteins contribute to cardiac plasticity during hibernation.
• Understanding these differences advances knowledge of mammalian adaptation and evolution.