从RAS系统研究“肾主生殖”的理论实质

"肾主生殖"是肾的主要功能.目前多从下丘脑-垂体-性腺轴解释这一理论机制,但肾脏与卵巢之间究竟有何内在联系尚未见报道.研究发现,肾脏与卵巢在胚胎发育期具有同源性,在生殖功能方面存在相似的调节系统.通过研究肾脏和卵巢内的RAS系统,对明确肾脏与卵巢内分泌功能的直接联系,探讨"肾主生殖"理论的客观物质基础具有重要意义.     

近端小管RAS功能轴在早期糖尿病小鼠肾脏中的变化

目的：观察自发性糖尿病小鼠模型中,糖尿病肾病早期近端小管肾素-血管紧张素系统（RAS）两条轴[血管紧张素转换酶（ACE）-血管紧张素II(Ang II)-血管紧张素II 1型受体（AT1）经典轴和ACE2-Ang(1-7)-Mas受体（MasR）新轴]的变化特征及对肾脏结构和功能的影响。方法：应用雄性自发性1型糖尿病Akita小鼠（以C57BL/6背景的雄性非糖尿病小鼠为正常对照）和自发性2型糖尿病db/db小鼠（以C57BLKS/J背景的雄性db/m非糖尿病小鼠为正常对照）,饲养至16周龄时处死小鼠,测定相应生理指标。收集尿液,检测尿液中Ang II和Ang(1-7)的含量;收取肾脏组织行病理切片染色观察肾脏结构变化;免疫组化法观察肾脏组织血管紧张素原（Agt）、ACE、ACE2和MasR的表达部位及变化;Western blot和RT-qPCR测定近端肾小管的上述蛋白及mRNA的变化。结果：两种糖尿病小鼠16周龄时,肾小球滤过率和尿白蛋白/肌酐比值显著增加（P<0.05）,PAS染色可见近端肾小管细胞体积增加,管腔扩张,肾小管肥大,肾小管损伤分数显著增加（P<0.01）...     

ACE/ACE2在AGT-REN双转基因高血压小鼠肾组织的表达变化及意义

目的: 观察血管紧张素原(AGT)-肾素(REN)双转基因高血压小鼠肾脏组织病理改变及血管紧张素转化酶(ACE)/血管紧张素转化酶2(ACE2)的表达变化,探讨ACE和ACE2在高血压肾损伤中的作用。方法: 实验分为4组,随机选择10月龄野生型、AGT转基因、REN转基因以及AGT-REN双转基因雄性C57小鼠各6只。每组动物颈动脉插管检测平均动脉压(MAP),1 h后处死小鼠;左侧肾脏置于10%中性甲醛固定,常规HE染色方法观察肾脏组织病理改变,免疫组化法观察肾脏ACE及ACE2的表达变化;右侧肾脏取出后放入蛋白裂解液中,提取蛋白,进行Western blotting实验,观察肾组织中ACE和ACE2蛋白表达。结果: 与野生型小鼠相比,AGT转基因小鼠MAP无明显变化(P>0.05),REN转基因小鼠MAP降低约15 mmHg(P<0.05);AGT-REN双转基因小鼠MAP明显升高约30 mmHg(P<0.05)。与野生型小鼠相比,AGT转基因和REN转基因小鼠肾组织未见明显病理改变,AGT-REN双转基因小鼠肾组织可见肾小动脉内膜及管壁显著增厚、管腔狭窄、纤维素样坏死、玻璃样变等典型恶性高血压肾损伤病理改变。免疫组化结果显示,与野生型小鼠相比,AGT转基因和REN转基因小鼠肾组织ACE和ACE2表达无明显差异(P>0.05),AGT-REN双转基因鼠肾组织ACE表达明显增高(P<0.05),而ACE2表达明显降低(P<0.05)。Western blotting结果显示:与野生型小鼠相比,AGT转基因鼠肾组织ACE和ACE2表达无明显变化;REN转基因鼠肾组织ACE表达无明显变化,ACE2表达稍降低(P<0.05);双转基因鼠肾组织ACE蛋白表达明显增强, ACE2蛋白表达水平显著降低,ACE/ACE2表达显著失衡。结论: AGT-REN双转基因可致小鼠恶性高血压,导致肾脏严重损伤;ACE/ACE2的表达失衡与血压改变密切相关,降低ACE或提高ACE2的表达可能对防治高血压具有重要意义。     

ACE2及其特殊功能

血管紧张素转换酶2(angiotensin-converting enzyme 2,ACE2)是新发现的与血管紧张素转换酶(ACE)相关的羧肽酶,在肾素-血管紧张素系统(rennin-angiotensin system,RAS)中ACE2可以使AngⅡ转换为Ang1-7,从而产生与血管紧张素Ⅱ相反的效应,同时ACE2还可使AngⅠ转换为Ang1-9 .研究发现:ACE2与高血压、SARS以及肾脏、生殖等系统的疾病有着密切的关系.     

肾素-血管紧张素系统基因多态性与2型糖尿病患者癌症发生的相关性

目的 探讨肾素-血管紧张素系统的基因多态性与2型糖尿病患者罹患癌症的关系.方法 对1282例无癌症病史的2型糖尿病患者检测了血管紧张素原(angiotensinogen,AGT)M235T、血管紧张素转换酶(angiotensin-converting enzyme,ACE) I/D和Ⅰ型血管紧张素Ⅱ受体(angiotensinⅡtype Ⅰ receptor,AGTR1)A1166C多态性.癌症终点事件诊断为在随访期间首次发生的致死性或非致死性癌症.癌症发生与基因变异的关联性应用Cox比例风险模型分析,并校正了常见混杂因素.结果 在11.7(四分位数间距:8.7 ～12.7)年随访期间,104例2型糖尿病患者(8.1％)罹患了癌症.罹患癌症的患者年龄更大、并多为男性.经年龄校正后,他们基线BMI、收缩压、总胆固醇、低密度脂蛋白胆固醇和肾小球滤过率比未罹患癌症的患者低;而腰臀围比、糖化血红蛋白和尿白蛋白/肌酐比值比未罹患癌症的患者高.Cox回归分析显示,校正基线混杂因素后,携带ACE Ⅰ/D DD基因型与癌症发生独立相关,与Ⅱ/ID基因型携带者比较,风险比为1.86(95％ CI1.03～3.38,P=0.036).结论 在中国2型糖尿病患者中,携带ACE Ⅰ/D DD基因型与癌症发生风险的增高显著相关.     

高静水压对血管内皮细胞ADMA水平的影响及RAS的作用

目的：观察体外压力培养对人脐静脉内皮细胞（HUVECs）非对称性NG-二甲基精氨酸（asymmetric NG, NG-dimethyl-L-arginine, ADMA ）代谢的影响。 方法:分大气压（APC，0 mmHg），中压（MPC，120 mmH g）和高压（HPC，180 mmHg）三组，各组分别用卡托普利（Cap, 10 μmol/L或100 μmol/L）和厄贝沙坦（Irb, 10 μmol/L或100 μmol/L）进行干预。测定β-N-乙酰氨基己糖苷酶活性以反映12 h细胞增殖。上清液用以测定ADMA的浓度（高效液相色谱法，HPLC）。 结果:①中、高压组ADMA浓度显著高于大气压组（0.75±0.05 vs 4.69 ±0.37和4.48±0.39，P<0.01），两压力组间无明显差异。②大气压时Cap与Irb对ADMA浓度无明显影响，而中、高压组药物使ADMA增加幅度减轻，且呈浓度依赖性趋势。 结论:压力刺激可使条件培养液中 ADMA的水平增加。抑制肾素-血管紧张素系统(re nin-angiotensin system, RAS)可以减轻ADMA增加，表明RAS激活参与压力诱导的ADMA代谢 异常。     

体外反搏对心肌缺血犬RAS的影响及与血流动力学的关系

目的:探讨心肌缺血与体外反搏(ECP)时犬局部肾素-血管紧张素系统(RAS)和血流动力学的改变以及它们之间的关系。方法:采用冠状动脉结扎法复制犬急性心肌缺血模型,检测缺血及外加反搏时缺血心肌、主动脉、肾脏、肺等局部肾素活性、血管紧张素Ⅱ(AngⅡ)水平和血管紧张素转换酶(ACE)活性,用八导生理记录仪记录血流动力学,分析它们之间的关系。结果:缺血能激活缺血区心肌、主动脉处肾素、ACE和AngⅡ,除缺血区心肌肾素外,ECP抑制缺血区心肌与主动脉处三者。缺血还能激活对循环RAS影响较大的肾脏与肺RAS,反搏对其有一定抑制作用。缺血与反搏时的血流动力学改变和心血管局部AngⅡ水平有关。结论:体外反搏治疗心肌缺血时,局部RAS和血流动力学状态的改变呈相关关系,即体外反搏对血流动力学的改善作用和能抑制局部RAS有关,这可能是它对缺血心肌起保护作用的机制之一。     

ACE2基因敲除小鼠止血带休克后肾组织ACE/AngⅡ表达的变化及其与肾损伤的关系

 目的： 通过观察血管紧张素转换酶2(ACE2)基因敲除(KO)小鼠止血带休克(TS)后肾组织血管紧张素转化酶/血管紧张素Ⅱ（ACE/AngⅡ）的表达及损伤程度的变化,探讨ACE2在休克后急性肾损伤中的作用。方法： 小鼠双下肢用止血带结扎缺血2 h、松带后再灌注4 h复制TS模型。将雄性6月龄野生型（WT）C57BL/6小鼠和相同背景的ACE2 KO小鼠各12只分为4组,即WT组、WT+TS组、KO组和KO+TS组,每组6只。Western blotting测肾组织ACE蛋白的表达;ELISA法测定肾组织AngⅡ表达;利用化学比色方法测定肾组织丙二醛（MDA）含量、超氧化物歧化酶（SOD）活性、血尿素氮（BUN）和血清肌酐（Cr）含量。结果： 与WT小鼠相比,WT+TS小鼠肾组织ACE/AngⅡ表达明显增加,出现肾组织氧化应激损伤和功能改变;与WT小鼠相比,KO小鼠肾组织ACE/AngⅡ表达增加,但未见明显的氧化应激损伤和功能变化;与WT+TS小鼠相比,KO+TS小鼠肾ACE/AngⅡ表达进一步增加,肾组织氧化应激和肾功能损伤明显加重。结论： ACE2基因缺失可能通过增加ACE/AngⅡ表达加重止血带休克肾的氧化应激损伤,针对ACE2靶f点的药物有可能成为防治止血带休克时急性肾损伤的策略之一。     

止血带休克后主动脉收缩反应性及RAS成分的变化

 目的: 通过观察止血带休克(tourniquet shock,TS)后主动脉收缩反应性及肾素-血管紧张素系统(renin-angiotensin system,RAS)的变化,探讨RAS稳态失衡在止血带休克后主动脉低反应性及损伤中的作用。方法: 8月龄C57BL/6的雄性小鼠,分为对照组及6个模型组,每组6只。模型组进行止血带套扎双后肢阻断血流,2 h后解套扎进行再灌注,分别于再灌注10 min、1 h、2 h、4 h、6 h和12 h后处死,对照组不进行套扎与再灌注,其余操作同模型组;多普勒血流仪测定肢体血流,颈动脉插管法测定平均动脉压(MAP),离体血管张力测定仪测定主动脉收缩反应性,HE染色结合透射电镜评价血管形态学损伤;Western blot检测血管组织中血管紧张素Ⅱ 1型受体(AT1受体)、血管紧张素(1-7)受体(Mas受体)、血管紧张素转换酶(ACE)和ACE2蛋白的表达。采用ELISA检测血清中血管紧张素Ⅱ(AngⅡ)和血管紧张素(1-7)[Ang(1-7)]的含量。结果: 与对照组相比,模型组出现下述变化:(1)随着再灌注时间的延长血流量逐渐减少;MAP在再灌注10 min明显升高,随后逐渐降低;血管对去甲肾上腺素的反应性在再灌注10 min升高随后下降,再灌注4 h的血管反应性最低;形态学损伤评分随再灌注时间延长逐渐增高;(2)主动脉AT1受体与ACE2蛋白表达逐渐下降,Mas受体与ACE蛋白表达逐渐升高;(3)血清中AngⅡ的含量整体呈升高趋势,Ang(1-7)的含量整体呈降低趋势。结论: 主动脉收缩反应性在休克初期暂时升高,随后降低,其发生机制可能与血管形态学损伤及RAS失衡有关。     

小鼠止血带休克后肾组织ACE/ACE2表达变化及意义

目的: 通过观察小鼠止血带休克(TS)后,不同时点血管紧张素转换酶(ACE)和血管紧张素转换酶2(ACE2)在肾脏的表达变化与肾损伤程度的关系,探讨ACE/ACE2表达失衡在TS后肾损伤中的作用。方法: 复制小鼠TS模型,Western blotting测肢体缺血再灌注后12 h内肾组织ACE和ACE2蛋白的表达;利用化学比色方法测定血清和肾组织丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性;制作肾病理切片,观察肾组织形态变化,并利用免疫组织化学方法观察ACE和ACE2的表达部位。结果: Western blotting结果显示,各时点与对照组比较,TS后ACE表达升高,ACE2表达降低;与对照组比较血清和肾MDA水平增高(P<0.05),SOD活性降低(P<0.05);HE病理切片显示,TS后各时点肾组织有充血、炎细胞浸润等不同程度损伤;免疫组化结果显示,ACE在肾小管上皮细胞胞浆表达,TS后表达明显增强;ACE2主要在肾小管上皮细胞管腔膜表达,TS后表达明显降低。结论: TS后肾组织ACE表达升高,ACE2表达降低,ACE/ACE2表达失衡可能与肾损伤有关。     

SPARC在db/db小鼠肾脏组织中高表达

目的 检测db/db鼠肾脏组织中的富含半胱氨酸的酸性分泌蛋白(SPARC)的表达情况.方法 RT-PCR、Western blot及免疫荧光方法检测db/db鼠肾脏组织中的SPARC mRNA及蛋白的表达.结果 SPARC在db/db鼠肾脏组织中呈现高表达.结论 db/db鼠肾脏组织中的SPARC呈现高表达(P＜0.05),可能与糖尿病肾病的发生与发展有关.     

Mibefradil reduces blood glucose concentration in db/db mice

OBJECTIVE:

Numerous recent studies suggest that abnormal intracellular calcium concentration ([Ca²⁺]_i) is a common defect in diabetic animal models and patients. Abnormal calcium handling is an important mechanism in the defective pancreatic β-cell function in type 2 diabetes. T-type Ca²⁺ channel antagonists lower blood glucose in type 2 diabetes, but the mechanism remains unknown.

METHODS:

We examined the effect of the Ca²⁺ channel antagonist mibefradil on blood glucose in male db/db mice and phenotypically normal heterozygous mice by intraperitoneal injection.

RESULTS:

Mibefradil (15 mg/kg, i.p., b.i.d.) caused a profound reduction of fasting blood glucose from 430.92±20.46 mg/dl to 285.20±5.74 mg/dl in three days. The hypoglycemic effect of mibefradil was reproduced by NNC 55-0396, a compound structurally similar to mibefradil but more selective for T-type Ca²⁺ channels, but not by the specific L-type Ca²⁺ channel blocker nicardipine. Mibefradil did not show such hypoglycemic effects in heterozygous animals. In addition, triglycerides, basal insulin and food intake were significantly decreased by mibefradil treatment in the db/db mice but not in the controls. Western blot analysis, immunohistochemistry and immunofluorescence staining showed a significantly increased expression of T-type Ca²⁺ channel α-subunits Cav3.1 and Cav3.2 in liver and brain tissues from db/db mice compared to those from heterozygous animals.

CONCLUSIONS:

Collectively, these results suggest that T-type Ca²⁺ channels are potential therapeutic targets for antidiabetic drugs.     

Leptin receptor expression in the dorsomedial hypothalamus stimulates breathing during NREM sleep in db/db mice

Study ObjectivesObesity leads to obstructive sleep apnea (OSA), which is recurrent upper airway obstruction during sleep, and obesity hypoventilation syndrome (OHS), hypoventilation during sleep resulting in daytime hypercapnia. Impaired leptin signaling in the brain was implicated in both conditions, but mechanisms are unknown. We have previously shown that leptin stimulates breathing and treats OSA and OHS in leptin-deficient ob/ob mice and leptin-resistant diet-induced obese mice and that leptin’s respiratory effects may occur in the dorsomedial hypothalamus (DMH). We hypothesized that leptin receptor LepR^b-deficient db/db mice have obesity hypoventilation and that restoration of leptin signaling in the DMH will increase ventilation during sleep in these animals.MethodsWe measured arterial blood gas in unanesthetized awake db/db mice. We subsequently infected these animals with Ad-LepR^b or control Ad-mCherry virus into the DMH and measured ventilation during sleep as well as CO₂ production after intracerebroventricular (ICV) infusions of phosphate-buffered saline or leptin.ResultsAwake db/db mice had elevated CO₂ levels in the arterial blood. Ad-LepR^b infection resulted in LepR^b expression in the DMH neurons in a similar fashion to wildtype mice. In LepR^b-DMH db/db mice, ICV leptin shortened REM sleep and increased inspiratory flow, tidal volume, and minute ventilation during NREM sleep without any effect on the quality of NREM sleep or CO₂ production. Leptin had no effect on upper airway obstruction in these animals.ConclusionLeptin stimulates breathing and treats obesity hypoventilation acting on LepR^b-positive neurons in the DMH.     

Impaired liver regeneration after partial hepatectomy in db/db mice

Fatty liver is the most common hepatic disorder in humans and supposed to be a cause of poor prognosis after liver transplantation and hepatic resection which could be resulted from impaired liver regeneration. This study was carried out to analyze the process of liver regeneration in db/db mice which show severe steatosis because of abnormal leptin receptor. We performed 70% partial hepatectomy (PH) on db/db mice and normal +m/+m mice, and then sacrificed the animals 1, 2, 3, 5, 7 and 10 days later. The liver samples were weighed and examined histologically or immunohistochemically. As a result, the liver mass restitution was significantly inhibited in db/db mice compared with +m/+m mice. The BrdU labelling index peaked at 2 days after PH in both strains, although the value was lower in db/db mice. After that, interestingly, it decreased to the control level at 5 days in +m/+m mice while the recovery was delayed in db/db mice. Similar sequence was also observed in the PCNA labelling index. In addition, the peak time of the mitosis index was 2 days and 5 days after PH in +m/+m mice and in db/db mice, respectively. Thus, although not significant, the proliferative response of hepatocytes to PH occurred somewhat more transient and sharply in +m/+m mice while it lasted somewhat longer in db/db mice. This suggests that db/db mice may be valuable as one of the animal models for the investigation of the effects of steatosis on the liver regeneration.     

绿原酸改善db/db小鼠血管内皮功能障碍的作用初探

目的:探讨绿原酸(CGA)对肥胖型2型糖尿病小鼠血管内皮功能障碍的作用并初步分析相关的机制。方法:雄性db/db小鼠12只,随机分对照组和CGA组,每组6只。CGA组以含0.02%CGA的饲料喂养,对照组给予普通饲料喂养,干预时间为12周。每周测空腹血糖、体重和鼠尾血压。实验结束后取血分离血浆,采用ELISA法测血红素氧合酶1(HO-1)、过氧化氢酶(CAT)、醌NAD(P)H脱氢酶1(NQO1)和谷胱甘肽过氧化物酶1(GPx-1)的水平。取胸主动脉以DHE和DAF-2 DA染色观察血管内膜超氧阴离子和一氧化氮(NO)水平,以Wire Myograph System观察胸主动脉张力,Western blot观察血管组织中核因子E2相关因子2(Nrf2)、过氧化物酶体增殖物激活受体α(PPARα)、磷酸化AMP活化蛋白激酶(p-AMPK)、磷酸化内皮型NO合酶(p-eNOS)、P22~(phox )和P47~(phox)的蛋白水平。结果:膳食CGA可显著降低小鼠的空腹血糖和体重,增加血浆中HO-1、CAT、NQO1和GPx-1水平,减少血管内皮超氧阴离子的水平,增加NO水平,改善小鼠血管内皮依赖性舒张功能(P0.01)。Western blot结果发现CGA可显著上调血管组织中PPARα、Nrf2、p-AMPK和p-eNOS的蛋白水平,降低P22~(phox )和P47~(phox)的水平(P0.01)。结论:膳食CGA显著改善db/db小鼠血管内皮依赖性舒张功能。这可能与其上调PPARα、Nrf2和AMPK等抗氧化应激分子,降低氧化应激水平,促进eNOS磷酸化有关,但确切机制尚需进一步研究。     

Differential effect of statins on diabetic nephropathy in db/db mice

Recent studies suggest a potential benefit of the lipid-lowering medication in the treatment of chronic kidney disease (CKD) such as diabetic nephropathy. Although statins have been widely used to lower serum cholesterol levels, the effect of these drugs on diabetic nephropathy has not been fully elucidated. In the present study, therefore, we addressed the role of different kinds of statins on diabetic nephropathy in db/db mice. Mice were fed with a standard diet with 0.005% (w/w) of pitavastatin, rosuvastatin, and pravastatin for 8 weeks starting from 8 weeks of age. The treatment with statins did not affect the food intake, body weight gain, adiposity, or blood pressure in db/db mice. Treatment with statins also had no effect on plasma lipid levels. In terms of the effect on albuminuria, pitavastatin and rosuvastatin reduced the urinary excretion of albumin by 60 and 40%, respectively, but not pravastatin, suggesting the effect of these two drugs on diabetic nephropathy. Furthermore, pitavastatin and rosuvastatin improved glomerular hypertrophy. All statins treatment improved insulin resistance. In addition, rosuvastatin and pravastatin treatment reduced oxidative stress measured by urinary 8-OHdG level, whereas the statins had no effect on the inflammatory response in the kidney of db/db mice. These results are not consistent with the renoprotective effect of statins. In conclusion, our data suggest that pitavastatin and rosuvastatin can improve diabetic nephropathy through the suppression of glomerular hypertrophy, independent of lipid-lowering or anti-oxidative effects.     

Blockade of IL-6 signaling exacerbates liver injury and suppresses antiapoptotic gene expression in methionine choline-deficient diet-fed db/db mice

Our previous study revealed that blockade of interleukin-6 (IL-6)-STAT3 signaling ameliorated liver injury, although hepatic STAT3(-/-) or GP130(-/-) mice have been reported to develop severe liver injury, in a murine methionine choline deficient (MCD) diet-induced model of non-alcoholic steatohepatitis (NASH). In this study, to determine whether profound blockade of IL-6-STAT3 signaling may still ameliorate liver injury, we studied db/db mice, which have impaired leptin-mediated STAT3 activation, using the MCD diet-induced NASH model. Male lean and db/db mice (6 weeks old) were fed either control chow or an MCD diet for 8 or 12 weeks. Half of the mice were treated with 15 mg/kg rat anti-mouse IL-6 receptor neutralizing antibody (MR16-1) intraperitoneally twice weekly, the remainder were injected with 15 mg/kg rat IgG as a control. Hepatic steatosis, injury, fibrosis, markers of lipid peroxidation/oxidant stress and antiapoptotic gene expression were evaluated. Plasma IL-6 levels were elevated in all groups of db/db mice. Although hepatic IL-6/ GP130 signaling was activated in chow-fed db/db mice, this was suppressed in MCD diet-fed db/db mice, accompanied by downregulation of hepatic IL-6 receptor and GP130 mRNA expression. MR16-1 treatment of MCD diet-fed db/db mice further repressed STAT3 activities and expression of STAT3-related antiapoptotic genes, such as Bcl-2 and Ref-1, but increased plasma-free fatty acid and hepatic markers of lipid peroxidation/oxidant stress, leading to increased liver injury, hepatocyte apoptosis and liver fibrosis. Although 'moderate' blockade of enhanced IL-6-STAT3 signaling may be beneficial in NASH, as we reported previously, these findings demonstrate that a profound defect in STAT3 activation is detrimental in terms of liver injury, hepatocyte apoptosis and liver fibrosis, indicating the hepato-protective role of IL-6 signaling in this severe NASH model.     

Ramipril improves oxidative stress-related vascular endothelial dysfunction in db/db mice

Endothelial dysfunction often precedes Type 2 diabetes-associated cardiovascular complications. One important cause of endothelial dysfunction is oxidative stress, which can lead to reduced nitric oxide (NO) bioavailability. In this study, we examined the effects of ramipril (an angiotensin-converting enzyme inhibitor, ACEI) on reactive oxygen species (ROS) production and endothelium-dependent vasodilation using a Type 2 diabetic (db/db) murine model. Plasma concentration of 8-isoprostane ([8-isoP]) was measured and used as an indication of the amount of ROS production. Six weeks of ramipril (10 mg/kg/day) treatment significantly reduced [8-isoP] and improved acetylcholine(ACh)-induced vasodilation in db/db mice without altering responses in wild-type (WT) mice. Responsiveness of smooth muscle cells to NO, assessed by sodium nitroprusside-induced vasodilation, was not different between db/db and WT mice regardless of ramipril or vehicle treatment. Our results suggest that ramipril specifically improved endothelium-dependent vasodilation in Type 2 diabetic mice, possibly by reducing ROS levels.