The vasodilatory action of telmisartan on isolated mesenteric artery rings from rats

OBJECTIVE(S): Angiotensin II type 1 receptor blockers (ARBs) represent one of the widely used antihypertensive agents. In addition to anti-hypertension effect, some ARBs also show other molecular effects such as activating peroxisome proliferator-activated receptor-γ and so on. Here we studied the effects of telmisartan on the rat isolated mesenteric artery rings pre-contracted by phenylephrine (PE). MATERIALS AND METHODS: Rat mesenteric artery rings were pre-contracted with 10 μM PE, and cumulative concentration-response curves to telmisartan were obtained. The endothelium-dependent mechanisms were investigated by mechanical removal of the endothelium. K(+) channels were investigated by pretreatment of the artery rings with various K(+) channel blockers. RESULTS: Telmisartan produced concentration-dependent relaxation of the artery rings pre-contracted by 10 μM PE. Denudation of the endothelium did not affect the relaxant effect of telmisartan. Pretreatment with BaCl(2) nearly inhibited the relaxation induced by the 0.5, 1, 5 and 10 μM telmisartan, but did not affect the relaxation induced by the 50 and 100 μM telmisartan. While the relaxation induced by telmisartan was not affected by pretreatment with TEA, 4-AP and glibenclamide. CONCLUSION: These findings demonstrated that telmisartan produces concentration dependent vasodilation in isolated rat mesenteric artery rings with or without endothelium pre-contracted by PE. K(IR) channel may be involved in such a relaxant effect of telmisartan.