N-乙酰-L-半胱氨酸对慢性间歇性缺氧大鼠血压变化及内皮功能的影响

 目的:观察N-乙酰-L-半胱氨酸(N-acetyl-L-cystein,NAC)对慢性间歇性缺氧（chronic intermittent hypoxia,CIH）大鼠的血压变化及其内皮功能变化,探讨CIH引起高血压的机制。方法:30只健康雄性Sprague-Dawley(SD)大鼠随机分成正常对照组、CIH组(缺氧55 s,复氧 55 s）及NAC干预CIH组（缺氧55 s,复氧55 s,NAC 300 mg·kg-1·d-1,灌胃）。尾套法测量大鼠尾动脉收缩压;实时荧光定量PCR测定胸主动脉内皮型一氧化氮合酶（endothelial nitric oxide synthase, eNOS）和内皮素1（endothelin-1, ET-1）mRNA的表达情况。使用Western blotting方法检测胸主动脉eNOS表达。胸主动脉及血清ET-1水平均采用放射免疫法测定。硝酸还原酶法测定血清中一氧化氮（nitric oxide,NO）含量。分别采用黄嘌呤氧化酶法和硫代巴比妥酸法测定外周血浆超氧化物歧化酶（superoxide dismutase, SOD）和丙二醛（malondialdehyde,MDA）水平。使用化学比色法测定胸主动脉组织匀浆中超氧阴离子(O-·2)含量。结果:CIH组大鼠尾动脉收缩压较对照组升高（P＜0.01）,NAC干预CIH组大鼠的尾动脉收缩压较CIH组显著降低（P＜0.05）。CIH组胸主动脉中eNOS mRNA和蛋白水平以及血清NO水平低于对照组（P＜0.01）,NAC干预组两者表达明显高于CIH组(P<0.05);CIH 组胸主动脉ET-1 mRNA和蛋白水平表达高于对照组（P＜0.01）,而NAC治疗使表达减低(P<0.05）。CIH组血清MDA和ET-1水平以及胸主动脉匀浆O-·2水平均高于对照组（P＜0.01）,而NAC干预组这些指标水平均低于CIH组（均P＜0.05）;CIH组血清SOD活性低于对照组（P＜0.01）,而NAC治疗组SOD活性增加（P＜0.05）。结论: NAC通过减少自由氧的产生,保护主动脉组织内皮功能,从而缓解血压升高,推测氧化应激参与CIH致高血压内皮功能障碍的发生机制。

Effect of N-acetyl-L-cystein on blood pressure and endothelial function in aorta of rats exposed to chronic intermittent hypoxia

AIM: To investigate the effect of N-acetyl-L-cystein (NAC) on blood pressure and endothelial function in the aorta of the rats exposed to chronic intermittent hypoxia (CIH). METHODS: Thirty healthy male SD rats were randomly divided into 3 groups: control group, CIH group and CIH+NAC group. The systolic blood pressure (SBP) was measured with tail-cuff me-thod. Real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) was used to detect the mRNA expression of endothelial nitric oxide synthase (eNOS） and endothelin-1 (ET-1) in the thoracic aorta. The protein expression of eNOS in the thoracic aorta was examined by Western blotting. The levels of ET-1 in the thoracic aorta and serum were detected by radioimmunoassay. The serum nitric oxide was determined by nitric acid reduction method.The superoxide dismutase (SOD) activity in peripheral blood plasma was detected by xanthine oxidase method.The serum malondialdehyde content was detected by thiobarbituric acid method, and superoxide anion (O-·2) in thoracic aorta was determined by chemical colorimetric method. RESULTS: Compared with the control animals, CIH exposure was associated with decreased SOD level, and NAC-treated CIH animals showed recovery in SOD level. NAC treatment prevented CIH-induced hypertension as well as CIH-induced increase in MDA. The aorta eNOS mRNA and protein, and serum NO levels in CIH group were lower than those in control group, and those in NAC treatment group were higher than those in CIH group. The increases in ET-1 mRNA,ET-1 protein and O-·2 levels in the aorta, and the elevated circulating ET-1 level were also observed in CIH-exposed animals. Treatment with NAC significantly decreased the mRNA and protein levels of ET-1, the O-·2 content, and  the circulating ET-1 level in CIH-exposed animals. CONCLUSION: NAC protects endothelial function and alleviates hypertension by suppressing the oxidant stress in the aorta tissues, indicating that oxidant stress may be involved in the mechanism of endothelial disorder of CIH-induced hypertension.