血压盐敏感者一氧化氮系统与非对称性二甲基精氨酸和补钾的作用

The Effect of Salt Loading on Plasma Asymmetric Dimethylarginine and NO and the Protective Role of Potassium Supplementation in Normotensive Salt-sensitives People

目的通过观察慢性盐负荷及补钾后血浆非对称性二甲基精氨酸(ADMA)和血、尿一氧化氮(NO)水平的变化及其与血压的关系,探讨血压正常盐敏感者(SS)的血管内皮功能损伤及补钾的保护作用。方法选60例年龄在20～60岁的血压正常者参与为期3周的慢性盐负荷及补钾试验,包括基线调查3d,低盐(LS)饮食,高盐(HS)饮食,和高盐补钾(HS+K)饮食各7d的研究。每个阶段均测量血压,并收集血、尿标本。血、尿NO用Griess法测量,血浆ADMA用高效液相色谱法测量。结果受试者60例中共检出SS13例,检出率为21.6%。盐负荷后,SS血浆ADMA的浓度明显升高[(0.89±0.09vs0.51±0.07)μmol/L,P<0.05],而血浆NO的水平则较LS饮食期显著降低[(41.8±7.6vs63.5±7.6)μmol/L,P<0.01]。在HS摄入的基础上大剂量口服补钾可以逆转单纯HS负荷对SS血浆ADMA浓度和血、尿NO水平的作用[(ADMA:0.52±0.09vs0.89±0.09)μmol/L;NO:(58.1±7.4vs41.8±7.6)μmol/L],血浆ADMA浓度和平均动脉压之间存在正相关关系。结论血压正常SS于HS负荷后伴随血压升高,血浆ADMA显著升高、NO降低,同时补充钾盐可以逆转前述作用,提示补钾可能通过抑制ADMA的升高降低血压。

Objective To investigate whether the plasma asymmetric dimethylarginine（ADMA） can be modulated by chronic salt loading in normotensive salt sensitive（SS） persons and its relationship with NO, and further determined the effect of potassium supplementation in diet. Methods Sixty normotensive subjects（aged from 20 to 60 years） were recruited, all people were sequentially maintained on a protocol with 7 days low salt diet （3 g/d, NaCl）, 7 days high salt diet （18 g/d）, and high salt diet with potassium supplementation（4.5 g/d, KCl） for another 7 days. In the end of each period, the plasma sample and 24 h urine were collected, the NO metabolite （NOx） were measured by Griess method. The plasma ADMA was measured by high-performance liquid chromatography. Results Thirteen persons with SS were found（21.6%） with remaining 47 persons as salt resistant（SR）. After salt loading, in salt sensitive subjects the plasma ADMA concentrations were elevated significantly in SS： 0.89±0.09 vs SR： 0.51±0.07 mol/L （P〈0.05）, while the plasma NO levels were decreased （SS：41.8±7.6 vs SR： 63.5 ± 7.6 μmol/L, P〈0.01 ）. Suprisingly, all the changes can be reversed by potassium supplementation （ ADMA： 0. 52±0. 09 vs 0. 89±0.09 and NO： 58.1±7.4 vs 41.8±7.6 μmol/L）. Plasma ADMA concentration and mean blood pressure was positively related. Conclusion The data clearly indicated that the plasma ADMA was significantly increased after salt loading in normotensive salt sensitives and correlated with mean blood pressure and NO. However potassium supplementation reverse these changes, suggesting that potassium supplementation may lower the blood pressure by inhibiting plasma ADMA.