Extra Virgin Olive Oil Phenols Dilate the Rat Mesenteric Artery by Activation of BK(Ca2+) Channels in Smooth Muscle Cells

Accumulating evidence has shown the beneficial health effects of extra virgin olive oil (EVOO) consumption in reducing blood pressure and preventing the risk of developing hypertension. Some studies associate the hypotensive activity of EVOO to a minor component—the phenols. This study was designed to investigate the effects of EVOO phenols on the rat resistance mesenteric artery (MA) and to find out the possible vascular pathways involved. The experiments were carried out using a pressurized myograph, which allowed the effects of phenols on isolated MA to be tested under different conditions: (a) with endothelium removed; (b) with inhibition of nitric oxide synthase by N(ω)-Nitro-l-arginine methyl ester hydrochloride (l-NAME, 10(−4) M) + N(ω)-Nitro-l-arginine (l-NNA, 10(−4) M); (c) with inhibition of cyclooxygenase by indomethacin (10(−5) M); (d) with inhibition of guanylate cyclase by 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ,10(−5) M) or adenylate cyclase by 9-(Tetrahydro-2′-furyl)adenine (SQ, 10(−5) M); (e) with depolarization by high potassium chloride (40 mM); and (f) with inhibition of the large conductance Ca(2+)–potassium channels (BK(Ca2+)) with paxilline (10(−5) M). EVOO phenols induce vasodilation of the endothelium, mediated by a direct effect on smooth muscle cells (SMC) by activation of BK(Ca2+) channels, an action by which phenols can regulate the vascular tone of the resistance artery. Phenols can be regarded as bioactive molecules that may contribute to the antihypertensive effects of EVOO.