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Ann Thorac Surg 1998;66:1318-1322
© 1998 The Society of Thoracic Surgeons

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Original articles: cardiovascular

Potassium-channel opener in cardioplegia may restore coronary endothelial function

^a Division of Cardiothoracic Surgery, Department of Surgery, University of Hong Kong, Grantham Hospital, Aberdeen, Hong Kong

Accepted for publication May 8, 1998.

Address reprint requests to Prof He, Division of Cardiothoracic Surgery, University of Hong Kong, Grantham Hospital, 125 Wong Chuk Hang Rd, Aberdeen, Hong Kong
e-mail: (gwhe{at}hkucc.hku.hk)

Background. Depolarizing (hyperkalemic) solutions impair the coronary endothelial function through an endothelium-derived hyperpolarizing factor mechanism. I examined the hypothesis that potassium-channel openers may restore the impaired endothelium-derived hyperpolarizing factor-mediated coronary vasorelaxation when added to hyperkalemic cardioplegia.

Methods. The porcine coronary arteries were exposed to hyperkalemia (potassium, 20 or 50 mmol/L) or hyperkalemia plus the potassium-channel opener aprikalim at 0.1 mmol/L for 1 hour. Endothelium-derived hyperpolarizing factor-mediated relaxation (percentage of 30 nmol/L U46619 precontraction) was induced by calcium ionophore A23187 and bradykinin in the presence of indomethacin (7 µmol/L) and N-nitro-L-arginine (300 µmol/L).

Results. The endothelium-derived hyperpolarizing factor-mediated relaxation was significantly impaired by exposure to hyperkalemia (20 mmol/L: 24.9% ± 14.1% versus 88.0% ± 3.3% in control, p = 0.002 for A23187; 50 mmol/L: 40.5% ± 12.3% versus 76.5% ± 3.8%, p = 0.003 for bradykinin). This reduced relaxation was significantly recovered by addition of aprikalim into the hyperkalemic (20 mmol/L) solution in A23187 experiments (81.2% ± 4.8%, p = 0.002) but only slightly recovered when added into the higher concentration of potassium (50 mmol/L) in bradykinin experiments (56.1% ± 4.7%, p = 0.2).

Conclusions. Potassium-channel openers may preserve endothelium-derived hyperpolarizing factor-mediated coronary relaxation when added to traditional hyperkalemic cardioplegia. This effect is significant when the potassium concentration is 20 mmol/L but partially lost when it reaches 50 mmol/L. This study may provide new insights into cardioprotection during open heart operations.

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