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pubmed:abstractText |
Potassium channel activators have potential cardioprotective properties, in part due to their ability to increase coronary blood flow. We compared the vasorelaxant properties of potassium channel activators, a calcium channel blocker (nicardipine) and a direct smooth muscle relaxant (sodium nitroprusside) in the canine coronary artery, the femoral artery and the saphenous vein precontracted with 0.03 microM endothelin-1. In the circumflex coronary artery, RWJ 29009, a novel and potent potassium channel activator, maximally relaxed the precontracted rings with an EC50 of 1.9 nM. Cromakalim (EC50 = 220 nM) and nitroprusside (EC50 = 109 nM) were also active. Nicardipine (EC50 = 16.6 nM) produced only a 70% relaxation at 1 microM concentration. In both femoral artery and saphenous vein, all agents relaxed the precontracted rings only at much higher concentrations, and the relaxations were only 75% of maximal relaxation. The results show that while all vasodilators preferentially relax the coronary artery, potassium channel activators appear to be the most selective and potent of these agents.
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