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Background Conducted vasodilation seems to be critical for the functional distribution of blood flow in the skeletal muscle microcirculation. However, this vasoregulatory phenomenon has not been documented in the coronary microcirculation, and its underlying mechanism remains elusive. Because potassium ions are potent metabolic vasodilators in the heart, by activating vascular inward rectifier K⁺ (K_ir) channels, we tested the hypothesis that coronary arterioles exhibit remote vasodilation through activation of this type of channel.

Methods and Results Porcine coronary arterioles were isolated, cannulated, and pressurized for in vitro study. Vessels dilated concentration-dependently to extraluminal KCl (5 to 20 mmol/L), bradykinin, adenosine, pinacidil, and sodium nitroprusside. A K_ir channel blocker, BaCl₂ (30 μmol/L), inhibited vasodilatory responses to KCl and bradykinin but not to adenosine, pinacidil, or …