β-adrenergic stimulation after rewarming does not mitigate hypothermia-induced contractile dysfunction in rat...

Area of Science:

• Cardiology
• Physiology
• Biochemistry

Background:

• Severe accidental hypothermia can cause hemodynamic instability due to cardiac contractile dysfunction.
• Catecholamines like epinephrine are used to treat this instability.
• Previous studies showed diminished epinephrine effects after hypothermia and rewarming (H/R).

Purpose of the Study:

• To investigate the impact of epinephrine on excitation-contraction coupling in isolated rat cardiomyocytes following H/R.
• To determine if epinephrine can mitigate H/R-induced cardiac contractile dysfunction.

Main Methods:

• Isolated adult male rat cardiomyocytes were electrically stimulated.
• Cytosolic calcium ([Ca2+]) and contractile responses (sarcomere length shortening) were measured.
• Cells underwent a H/R protocol (cooling to 15°C for 2h, then rewarming to 37°C) before epinephrine treatment assessment.

Main Results:

• At 37°C, epinephrine increased cardiomyocyte [Ca2+] and contractility concentration-dependently.
• After H/R, contractile responses were reduced, and [Ca2+] was slightly elevated.
• Epinephrine (25 nM) did not improve the diminished contractile response post-H/R and did not increase [Ca2+].

Conclusions:

• Epinephrine treatment does not mitigate hypothermia and rewarming-induced contractile dysfunction in cardiomyocytes.
• The study highlights impaired cellular mechanisms underlying cardiac dysfunction after H/R.