Comparative Effect of Type 1 and Type 2 Diabetes Mellitus on Vascular Responses of Rat Thoracic Aorta to Potassium Ion Channel Openers

Background: Diabetes mellitus is associated with many cardiovascular dysfunction and impairment of potassium channel function.
Aim: We compared the vascular reactivity in aorta from streptozotocin-induced and Goto-Kakizaki (GK) diabetic rats to potassium channel openers.
Methodology: Diabetes mellitus (DM) was induced in Sprague Dawley rats by intraperitoneal injection of streptozotocin (STZ) at 65 mg/kg body weight. After four weeks of DM, vascular reactivity of the aortic rings from STZ-induced Sprague Dawley and age-matched GK and control rats to phenylephrine, acetylcholine, levcromakalim and naringenin was studied using standard organ bath procedure.
Results: The phenylephrine-induced contraction was significantly (P<0.05) increased in STZ-diabetic aortic rings [2.03 ±0.07 g] when compared with GK rats [1.47±0.14 g] and STZ-control [1.42±0.21 g]. Maximal relaxation and potency to acetylcholine, levcromakalim and (+/-)-naringenin were significantly (P<0.05) decreased in STZ- diabetic aorta when compared with GK-diabetic and control groups.
Conclusion: The phenylephrine-induced contraction, endothelium-dependent relaxation, KATP - and (+/-)-naringenin-induced vasorelaxation are not altered in the early stages of Type 2 diabetes whereas there is exaggerated contractile response and a relaxant dysfunction involving the endothelium, KATP in Type 1 diabetes mellitus.