Evaluation of the Effect of Myricetin on Contractile Reactivity of Thoracic Aorta in Streptozotocin-Diabetic Rats

Diabetes mellitus is accompanied with higher incidence of cardiovascular disorders. Due to antioxidant activity of the flavonoid myricetin, this study was conducted to evaluate its effect on contractile and relaxation response of thoracic aorta in diabetic rats and to determine the role of oxidative stress. In this experimental study, male Wistar rats were divided into 4 groups, i.e. control, myricetin-treated control (1 mg/kg), diabetic, and myricetin-treated diabetic groups (1 mg/kg). Myricetin was daily administered (i.p.) ten days after streptozotocin injection for 3 weeks. At the end of study, contractile reactivity of thoracic aortic rings to KCl and phenylephrine and relaxation response to acetylcholine was determined using isolated tissue setup. In addition, malondialdehyde (MDA) and nitrite were assessed in aortic tissue. Myricetin -treated diabetic group showed a non-significantly lower maximum contraction to KCl and a significantly lower maximum contraction to phenylephrine (p<0.05) as compared to diabetic group. Meanwhile, maximum relaxation response of rings to acetylcholine was significantly higher in myricetin-treated diabetic group as compared to diabetics (p<0.05). In addition, there was also a lower contractile response to PE in myricetin-treaded control and a higher relaxation response for myricetin-treated control group versus controls (p<0.05). In addition, significant reduction of MDA and nitrite (p<0.05) were observed in treated-diabetic rats. Administration of myricetin could decrease contractile response to PE and enhance relaxation response in aortic tissue of diabetic rat and this may be beneficial in prevention of long-term vascular complications of diabetes and part of its effect is via reducing oxidative stress.