Activation of the K+ channel BK(Ca) is involved in the relaxing effect of propofol on coronary arteries

BACKGROUND AND OBJECTIVE: Propofol may cause undesirable hypotension due to vasodilation. The underlying mechanisms are not completely understood. We investigated the mechanisms by which propofol relaxes vascular segments. METHODS: We studied the effect of propofol on isolated porcine coronary artery rings precontracted with potassium chloride or prostaglandin F2alpha. RESULTS: Propofol, in a concentration-dependent manner, relaxed all segments at concentrations of 5 microg mL(-1) and above. This relaxation was unaltered in the presence of N(omega)-nitro-L-arginine, indomethacin, diltiazem and glibenclamide. Tetraethylammonium chloride, an inhibitor of the BK(Ca) K+ channel (a high conductance Ca2+-sensitive K+ channel), dose-dependently attenuated the vasodilating effect of propofol (P < 0.001). CONCLUSIONS: Our results suggests that the activation of the BK(Ca) channel may contribute to the vasodilating effect of propofol, hereby causing hyperpolarization of the smooth muscle membrane and reduction of smooth muscle tone.