Introduction & Objective: Vascular complications represent the main cause of mortality in diabetic patients. Considering the role of plants containing flavonoids in elimination of diabetic vascular disorders and the protective effect of the aqueous extract of Artemisia annua on aortic contractile response in diabetic rats, we evaluated the mechanism of vasodilating action of Artemisia annua extract in this study.

Materials & Methods: For this purpose, male Wistar rats (n=36) were randomly divided into control, untreated-diabetic, and Artemisia annua aqueous extract treated-diabetic groups. For induction of diabetes, streptozotocin (STZ) was intraperitoneally administered (60 mg/Kg). Artemisia annua extract-treated group received 60 mg/Kg of extract intraperitoneally. After one month, contractile reactivity of aortic rings to phenylephrine in the presence of L-NAME and EGTA was determined using isolated tissue setup.

Results: Comparing of the contractile response of aortic rings with endothelium to phenylephrine, before and after adding of L-NAME, showed a significant difference between treated and untreated diabetic rats(P<0.05). On the other hand, comparing of aortic contractile response with or without endothelium to phenylephrine in the calcium-free Krebs in the presence of EGTA showed that the difference between treated- and untreated-rats was considerable (P<0.05).

Conclusion: On the basis of obtained results, it seems that the vasodilatory effect of aqueous extract of Artemisia annua on aortic rings in diabetic rats is an endothelium-dependent effect and acts through production and release of NO. Moreover it exerts its protective effect via inhibition of Ca²⁺ release from intracellular stores.