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

Objective(s): Angiotensin Ⅱ type ۱ 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 ۱۰ 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 ۱۰ μM PE. Denudation of the endothelium did not affect the relaxant effect of telmisartan. Pretreatment with BaCl۲ nearly inhibited the relaxation induced by the ۰.۵, ۱, ۵ and ۱۰ μM telmisartan, but did not affect the relaxation induced by the ۵۰ and ۱۰۰ μM telmisartan. While the relaxation induced by telmisartan was not affected by pretreatment with TEA, ۴-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. KIR channel may be involved in such a relaxant effect of telmisartan.

Keywords:

ARB , Potassium channel , Mesenteric arteries , Rat , Telmisartan , Vasodilation