Endothelium-dependent and-independent relaxation induced by resveratrol in rat superior mesenteric arteries

Abstract

Resveratrol (Res) is a specific agonist of sirtuin 1, and has many cardioprotective effects. Although Res is able to relax various vascular beds, its pharmacological properties in rat superior mesenteric arteries and the underlying mechanism are not well clarified. The aim of present study was to investigate the vasorelaxant effects of Res on rat superior mesenteric arteries and the mechanisms involved. The isometric tension of rat superior mesenteric arterial rings was recorded in vitro using myography. It was found that Res concentration-dependently relaxed endothelium-intact superior mesenteric artery rings pre-contracted by phenylephrine hydrochloride (E_max, 97.66±0.79%; pD₂, 4.30±0.14) or KCl (E_max, 101.3±0.6%; pD₂, 4.12±0.03). The vasorelaxant effect of Res on the superior mesenteric artery rings was partially endothelium-dependent. N^G-nitro-L-arginine methyl ester (100 µM) significantly inhibited the Res-induced vasorelaxant effect. However, 1H-[1,2,4]oxadiazolo[4,3-a] quinoxalin-1-one (10 µM) and indomethacin (5 µM) each had no effect on the Res-induced vasorelaxation. In artery rings without endothelium, the vasorelaxation induced by Res was attenuated by 4-aminopyridine (100 µM) and glibenclamide (10 µM). However, barium chloride dehydrate (10 µM) and tetraethylammonium chloride (1 mM) did not affect the vasorelaxation induced by Res. Moreover, Res also inhibited the contraction induced by an increase in external calcium concentration in Ca²⁺-free medium plus KCl (60 mM). These results suggest that Res induces relaxation in superior mesenteric arterial rings through an endothelium-dependent pathway, involving nitric oxide release, and also through an endothelium-independent pathway, with opening of voltage-dependent K⁺ channels and ATP-sensitive K⁺ channels and blockade of extracellular Ca²⁺ influx.

Keywords: Ca2+ influx; K+ channel; nitric oxide; resveratrol; superior mesenteric artery; vasorelaxant effects.

Figure 1.

Vasodilatation effects of resveratrol on endothelium-intact superior mesenteric arterial rings pre-contracted with (A) KCl (60 mM) or (B) PE (10 µM). Data are presented as mean ± standard error of the mean (n=6–8). *P<0.05 and **P<0.01 vs. DMSO. PE, phenylephrine hydrochloride; DMSO, dimethylsulfoxide.

Figure 2.

Vasodilatation effects of resveratrol on endothelium-intact and endothelium-denuded superior mesenteric arterial rings pre-contracted with (A) KCl (60 mM) or (B) PE (10 µM). Data are presented as mean ± standard error of the mean (n=6–8). *P<0.05 for Endo+ vs. Endo-. Endo+, artery ring with endothelium; Endo-, artery ring without endothelium. PE, phenylephrine hydrochloride.

Figure 3.

Vasodilatation effects of resveratrol (Res) on endothelium-intact superior mesenteric arterial rings pre-contracted with KCl (60 mM) in the presence of (A) the endothelial nitric oxide synthase inhibitor (L-NAME, 100 µM), (B) the cyclooxygenase inhibitor (Indo, 5 µM) and (C) the guanylate cyclase inhibitor (ODQ, 10 µM). Data are presented as mean ± standard error of the mean (n=6–8). *P<0.05 vs. Res. L-NAME, N^G-nitro-L-arginine methyl ester; Indo, indomethacin; ODQ, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one.

Figure 4.

Vasodilatation effects of resveratrol (Res) on endothelium-denuded superior mesenteric arterial rings pre-contracted with KCl (60 mM) in the presence of the K⁺ channel blockers (A) 4-aminopyridine (4-AP; 100 µM), (B) barium chloride dehydrate (BaCl₂, 10 µM), (C) glibenclamide (Gli; 10 µM) and (D) tetraethylammonium chloride (TEA; 1 mM). Data are presented as mean ± standard error of the mean (n=6–8). *P<0.05.

Figure 5.

Inhibitory effect of resveratrol on (A) intracellular Ca²⁺ release induced by PE (10 µM) and (B) extracellular Ca²⁺ influx induced by KCl (60 mM) in Ca²⁺-free solution in endothelium-denuded superior mesenteric arterial rings. Data are presented as mean ± standard error of the mean (n=6–8). **P<0.01 vs. control. PE, phenylephrine hydrochloride.