Tolerance of epicardial coronary endothelium and smooth muscle to hyperkalemia

Area of Science:

• Cardiovascular Physiology
• Endothelial Function
• Organ Preservation

Background:

• Previous studies suggest high potassium (K+) in cardioplegic solutions may harm the coronary endothelium.
• Direct functional changes in endothelium due to hyperkalemia remain understudied.

Purpose of the Study:

• To investigate the effect of varying K+ concentrations in physiologic and cardioplegic solutions on porcine coronary artery endothelium and smooth muscle.
• To assess the impact of exposure duration on these functional changes.

Main Methods:

• Porcine coronary artery rings were exposed to Krebs' or St. Thomas' solutions with different K+ concentrations (5.9-50 mmol/L) for 2 or 4 hours.
• Endothelial function was assessed by measuring endothelium-derived relaxing factor (EDRF) release in response to substance P.
• Smooth muscle function was evaluated via K+-induced contraction and glyceryl trinitrate-induced relaxation.

Main Results:

• High K+ concentrations (up to 50 mmol/L) in both solutions did not significantly decrease the maximal relaxation induced by substance P, indicating preserved endothelial function.
• No significant impairment of smooth muscle function was observed based on contraction or relaxation responses.

Conclusions:

• Hyperkalemia, at concentrations found in cardioplegic solutions, does not appear to directly impair endothelial or smooth muscle function in porcine coronary arteries under non-ischemic conditions.
• Findings suggest that the coronary endothelium may be more resilient to hyperkalemia than previously inferred from coronary flow rate changes.