Health Innovation Research Institute, RMIT University, Bundoora, Victoria, Australia.
Br J Pharmacol. 2011 Jan;162(2):365-77. doi: 10.1111/j.1476-5381.2010.01023.x.
To investigate whether diabetes affects either or both nitric oxide (NO)-mediated and endothelium-derived hyperpolarizing factor (EDHF)-type relaxation in endothelium-dependent relaxation of mesenteric arteries from streptozotocin-induced diabetic rats.
Wire myography was employed to examine endothelial function of mesenteric arteries. Superoxide levels were measured by L-012 and lucigenin-enhanced chemiluminescence. Western blotting was used to quantify protein expression levels.
Superoxide levels were significantly increased in diabetic mesenteric arteries compared with normal arteries. Diabetes significantly reduced the sensitivity to the endothelium-dependent relaxant, acetylcholine (ACh) in mesenteric arteries. When the contribution of NO to relaxation was abolished by N-nitro-L-arginine (L-NNA) + a soluble guanylate cyclase inhibitor (ODQ), the sensitivity to ACh was significantly decreased in the diabetic arteries compared with normal arteries, indicating an impaired EDHF-type relaxation despite increased expression of intermediate- and small-conductance calcium-activated potassium channels. Conversely, when the contribution of EDHF was inhibited with TRAM-34 + apamin + iberiotoxin, maximum relaxations to ACh were significantly decreased in diabetic compared with normal arteries, suggesting that the contribution of NO was also impaired by diabetes. Basal levels of NO release, indicated by contraction to L-NNA, were also significantly decreased in diabetic arteries. Western blot analysis demonstrated that diabetic arteries had an increased expression of Nox2, decreased pSer⁴⁷³ Akt and a reduced proportion of endothelial NO synthase (eNOS) expressed as a dimer, indicating uncoupling.
The contribution of both NO and EDHF-type relaxations was impaired in diabetes and was caused by increased oxidative stress, decreased pSer⁴⁷³ Akt and/or eNOS uncoupling.
研究糖尿病是否影响一氧化氮（NO）介导的和内皮衍生超极化因子（EDHF）型松弛在链脲佐菌素诱导的糖尿病大鼠肠系膜动脉内皮依赖性松弛中的作用。
采用有线测微技术研究肠系膜动脉的内皮功能。采用 L-012 和荧光素增强化学发光法测量超氧化物水平。采用 Western blot 测定蛋白表达水平。
与正常动脉相比，糖尿病大鼠肠系膜动脉中超氧化物水平显著升高。糖尿病显著降低了肠系膜动脉对内皮依赖性松弛剂乙酰胆碱（ACh）的敏感性。当用 N-硝基-L-精氨酸（L-NNA）+可溶性鸟苷酸环化酶抑制剂（ODQ）消除 NO 对松弛的贡献时，糖尿病动脉对 ACh 的敏感性较正常动脉显著降低，表明尽管中、小电导钙激活钾通道表达增加，但 EDHF 型松弛受损。相反，当用 TRAM-34+apamin+iberiotoxin 抑制 EDHF 作用时，糖尿病与正常动脉相比，ACh 的最大松弛作用显著降低，表明糖尿病也损害了 NO 的作用。由 L-NNA 引起的 NO 释放的基础水平（以收缩表示）在糖尿病动脉中也显著降低。Western blot 分析表明，糖尿病动脉中 Nox2 表达增加，pSer⁴⁷³Akt 减少，作为二聚体表达的内皮型一氧化氮合酶（eNOS）比例降低，表明脱偶联。
糖尿病时 NO 和 EDHF 型松弛的作用均受损，这是由氧化应激增加、pSer⁴⁷³Akt 减少和/或 eNOS 脱偶联引起的。
