Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout.

Area of Science:

• Cardiovascular Physiology
• Comparative Physiology
• Fish Biology

Background:

• Cold temperatures impair vertebrate heart function and contractility.
• Fish, like rainbow trout, exhibit seasonal cold acclimation, requiring physiological adjustments.
• Understanding these adaptations is crucial for comprehending thermal tolerance in ectotherms.

Purpose of the Study:

• To test if rainbow trout increase cardiac contractility during cold acclimation.
• To investigate the underlying mechanisms of cardiac compensation to cold.
• To identify strategies for enhancing cardiac muscle force generation.

Main Methods:

• Thermal acclimation of rainbow trout to 4°C, 11°C, and 17°C.
• Measurement of Ca(2+) sensitivity of force in chemically skinned cardiac trabeculae.
• Assessment of ventricular pressure generation using a Langendorff preparation.

Main Results:

• Cardiac trabeculae from 4°C-acclimated trout showed significantly higher Ca(2+) sensitivity of force.
• This increased sensitivity correlated with decreased cardiac troponin T phosphorylation.
• Hearts from 4°C-acclimated trout exhibited greater magnitude and rate of ventricular pressure generation.

Conclusions:

• Enhanced myofilament function, due to contractile protein modification, contributes to increased cardiac pressure generation in cold-acclimated trout.
• Rainbow trout employ phenotypic plasticity to increase cardiac muscle force-generating capacity in response to cold.
• This study reveals an in vivo strategy for improving cardiac muscle function under cold conditions.