Endothelium-dependent effect of Amaranthus caudatus feeding on contractile properties of thoracic aorta from diabetic rats

Diabetes mellitus is accompanied with higher incidence of cardiovascular disorders. There is some evidence of antidiabetic and vascular function-improving potential of Amaranthus caudatus (AC). Endothelium-dependent effects of oral administration of AC for 8 weeks on contractile and relaxatory response of thoracic aorta from diabetic rats were investigated. Wistar rats were divided into control, AC-treated control, diabetic, AC-treated diabetic, and glibenclamide-treated diabetic groups. For induction of type 1 diabetes, streptozotocin at a dose of 60 mg/kg (i.p) was injected. Treated groups received AC-mixed pelleted food at a weight ratio of 6.25%. Body weight and serum glucose level was measured before the study and after 4 and 8 weeks. At the end of study, contractile reactivity of thoracic aortic rings to KCl and phenylephrine and relaxatory response to acetylcholine and sodium nitroprusside was determined using isolated tissue setup. Serum glucose level significantly decreased in AS-treated diabetic group (P<0.05) versus untreated diabetics. In addition, endothelium-intact AC-treated diabetic group showed a significantly lower contraction to KCl and phenylephrine (P<0.01) as compared to diabetic group and endothelium removal abolished this response. Meanwhile, relaxation response of endothelium-intact rings to acetylcholine was significantly higher in AC-treated diabetic group as compared to diabetics (p<0.01). In addition, there were no significant changes amongst the groups regarding relaxatory response to sodium nitroprusside. Chronic oral administration of AC through affecting endothelial-related agents could decrease contractile response and enhance relaxatory response in aortic tissue of diabetic rat and this may be beneficial in prevention of long-term vascular complications of diabetes.