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老年人高血压Ouabain抵抗现象与肾素-血管紧张素系统的关系及硝苯啶干预的效应*
http://www.100md.com 《第三军医大学学报》 1999年第10期
     作者:谭建聪 祝之明 刘光耀 祝善俊 刘晓莉 胡厚祥 王海燕

    单位:谭建聪 祝之明 刘光耀 胡厚祥 王海燕(第三军医大学附属大坪医院野战外科研究所心血管内科、高血压研究中心) 重庆,400042;祝善俊(附属新桥医院心血管内科 重庆,400037 ;刘晓莉(第三军医大学附属大坪医院野战外科研究所心血管内科、高血压研究中心 肾内科) 重庆,400042)

    关键词:高血压;肾素-血管紧张素系统;哇巴因;硝苯啶

    第三军医大学学报991006 提 要 目的:探讨老年人高血压哇巴因(Ouabain)抵抗现象机制及其与肾素、血管紧张素系统(RAS)的关系。方法:47例高血压病(EH)病人, 分为老年EH组和非老年EH组,选择25名健康老年人作对照组。采用放射免疫分析法测定血浆肾素活性(PRA)、血管紧张素Ⅱ(AⅡ)、血浆内源性类地高辛物质(EDLS)浓度、EDLS与红细胞结合率(RBC-D%);测定加Ouabain后红细胞内Na+浓度([Na+]i)变化,计算出Ouabain敏感Na+外流速度常数(oKos),反映总的Na+ 泵活性;红细胞[Na+]i用火焰光度法测定。老年EH组和非老年EH组服硝苯啶治疗4周后复查。结果:老年EH组和非老年EH组RBC-D%、oKos下降,EDLS升高,但老年EH组RBC-D%、PRA、AII明显低于非老年EH组,血浆EDLS 和oKos高于非老年EH组,Na+泵活性呈现Ouabain抵抗现象。在老年EH组中,AII与收缩压、年龄和RBC-D%呈负相关,PRA与EDLS呈负相关;在非老年EH组中,血压与EDLS呈负相关。降压治疗后,老年EH病人PRA、AII、Na+ 泵活性升高,EDLS有下降趋势;中年EH者仅Na+泵活性升高,EDLS有升高趋势,PRA、AII无显著变化。结论:老年EH病人EDLS与细胞膜亲合力下降,呈现Ouabain抵抗现象,通过影响钠代谢抑制PRA、AII分泌。钙拮抗剂降压治疗可部分改善这种异常。
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    中图法分类号 R544.1 文献标识码:A

    The effects of nifedipine on ouabain-resistant phenomenon and renin-angiotensin system in elderly cases of essential hypertension*

    Tan Jiancong,Zhu Zhiming, Liu Guangyao,Zhu Shanjun, Liu Xiaoli,Hu Houxiang, Wang Haiyan (Researh Center of Hypertension, Department of Cardiology, Daping Hospital, Third Military Medical University,Chongqing,400042)

    Abstract Objective:To study the mechanism of ouabain-resistant phenomenon and its relationship with renin-angiotensin system in elderly cases of essential hypertension (EH). Methods: 47 cases of essential hypertension were divided according to their age into aged patients (AP,24) and nonaged patients (NAP,23) groups. 25 aged healthy individuals served as normotensive control. Plasma renin activity (PRA), angiotensin Ⅱ(AⅡ), endogenous digoxin-like substance (EDLS) and the binding rate of EDLS with red blood cells (RBC-D%) were determined with radioimmunoassay. The intra-erythrocytic Na+ concentration after 2 h incubation with ouabain was determined, and half of the value of intraerythrocytic Na+ concentration increase was considered as the rate constant of ouabain-sensitive Na+ efflux (oKos/h). Intraerythrocytic Na+ concentration was measured with flame photometry. After the administration of nifedipine for 4 weeks, the hepertensive cases were examined again. Results: oKos and RBC-D% were significantly lower and the plasma level of EDLS significantly higher in AP and NAP groups than in the control. Significantly higher plasma EDLS and oKos and lower RBC-D% and PRA were found in AP group than in NAP group. The Na+ pump in the AP group showed an ouabain-resistant phenomenon. All the findings were negatively correlated to the age and systolic pressure of the patients and the changes of RBC-D% and PRA were negatively correlated to those of EDLS. In the NAP group, the changes of blood pressure were negatively correlated to those of EDLS. After 4 weeks of nifedipine treatment, Na+ pump activity, PRA and other parameters were increased in the AP group but only Na+ pump activity was increased in the NAP group.Conclusions:Our findings indicated that the affinity of EDLS with cellular membrane is decreased in aged patients with EH, which is known as the ouabain-resistant phenomenon. Ouabain resistance inhibits the secretion of renin and angiotensin through its effects on sodium metabolism and nifedipine can partially correct this abnormality.
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    Key words hypertension; ouabain; renin-angiotensin system; nifedipine.

    既往的研究结果显示,老年人高血压病(Essential hypertension,EH)大多为低肾素型,肾素-血管紧张素系统(Renin angiotensin system, RAS)活性随年龄增长而降低。血浆肾素活性(Plasma reninactivity, PRA)、血管紧张素Ⅱ(Angiotensin Ⅱ, AⅡ)是调节人体血压、水电解质平衡的重要物质,为何在老年人EH中被抑制,机制不清。近年发现EH病人血浆内源性类地高辛物质(Endogenous digoxin-like substances, EDLS)浓度增高[1],EDLS同样具有调节人体血压、水电解质平衡的作用,尚不清楚它与RAS怎样相互作用影响血压。为此,我们观察了老年(Aged patient,AP)、非老年(Non-aged patient,NAP)EH病人服硝苯啶治疗前后血浆EDLS浓度、EDLS与红细胞结合率(RBC-D%)、红细胞Ouabain敏感Na+外流速度常数(The rate content of ouabain-sensivitive sodium efflux, oKos)、PRA、AII等,初步探讨了老年人高血压Ouabain抵抗现象机制及与RAS的关系。
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    1 对象与方法

    1.1 对象


    47例EH病人中,老年EH病人24例[年龄60~78岁,平均年龄(66±7)岁,其中男13例,女11例];非老年EH病人23例[年龄40~59岁,平均年龄(51±8)岁,其中男13例,女10例]。EH判断标准:收缩压(SBP)≥18.7 kPa及/或舒张压(DBP)≥12 kPa。全部病例均经详细询问病史、查、实验室检查,剔除继发性EH。检查前停服所有药物4周。取血标本后,予硝苯啶口服治疗(10~20 mg,3次/d),4周后复查。选择25名健康老年人作对照组[年龄60~74岁,平均年龄(65±5)岁,其中男13名,女12名]。

    1.2 方法

, 百拇医药     早晨空腹抽取静脉血,用肝素抗凝,将标本置于4°C、2500×g离心10 min,分别取血浆和红细胞作下述测定。

    1.2.1 血浆EDLS、PRA、AII浓度采用放射免疫分析法(由上海放射免疫分析技术研究所*****、PRA、AII放射免疫分析试剂盒)。

    1.2.2 EDLS 与红细胞结合率(红细胞-125I-地高辛结合率,RBC-D%)测定,采用放射免疫分析法,按文献[2]方法测定。取0.1 ml洗涤过的红细胞加125I-地高辛0.1 ml,生理盐水0.1 ml混匀,4°C 过夜,离心去上清,用GC-1820型γ计数器(中国科技大学)测定红细胞cpm,按下式计算:

    式中A为0.1 ml 125I-地高辛cpm,B为红细胞-125I-地高辛cpm,C为本底cpm。
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    1.2.3 红细胞哇巴因敏感钠外流速度常数(oKos)测定[3], 取全血加哇巴因(0.1 mmol/L)37°C水浴2 h,细胞内Na+ 浓度([Na+]i)升高的一半为哇巴因敏感钠外流(Ouabain sensitive sodium efflux,oMos,mmol/h.kg-1)。[Na+]i 用HG-3型火焰光度计测定。oKos 按下式计算。

    式中[Na+]w 为洗涤过的红细胞[Na+]i 。哇巴因敏感钠外流是Na+泵活动所致,因此,oKos 反映总的Na+ 泵活性。
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    1.3 统计分析

    所有数据用未配对资料t检验和相关分析处理。结果用x±s表示。

    

    2 结果


    2.1 研究对象的临床特点

    老年EH病人收缩压、平均动脉压(MAP)高于非老年EH病人,但舒张压低于非老年EH病人MAP,体重指数(Body mass index,BMI)2组无明显差别,见表1。

    表1 研究对象的临床特点

    Tab 1 Clinical characteristics of the study population Group
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    n

    Sex(M/F)

    Age

    SBP(kPa)

    DBP(kPa)

    MAP(kPa)

    BMI(kg/m2)

    Control

    25

    13/12

    65±5

    16.8±1.20
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    10.4±0.67

    12.4±1.07

    23.3±2.0

    AP

    24

    13/11

    66±7#

    25.6±4.27*#

    12.4±1.20*#

    18.8±1.87*#

    25.4±2.4
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    NAP

    23

    13/10

    51±8

    23.5±2.80*

    13.6±1.20*

    16.4±1.47*

    24.7±3.3

    *:P<0.01 vs control;#:P<0.05 vs NAP

    2.2 降压治疗前后各参数结果
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    治疗前老年EH病人血浆EDLS浓度、oKos高于非老年EH病人,RBC-D%、PRA、AII低于非老年EH病人,2组EH病人血浆EDLS浓度均高于正常对照组,oKos、 RBC-D%、 PRA、AII均低于正常对照组,[Na+]i 3组间无显著差别,见表2。

    治疗后老年EH组PRA、AII、oKos升高,EDLS略降低但未达显著水平。非老年EH组PRA、AII无明显变化,oKos升高,EDLS略升高但未达显著水平,见表2。

    表2 对照组、老年EH组和非老年EH组降压治疗前后各参数结果

    Tab 2 The results of different parameters before and after treatment with nifedipine Parameters
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    Control

    AP

    NAP

    Befor treatment

    After treatment

    Before treatment

    After treatment

    SBP(kPa)

    16.8±1.20

    25.6±4.27**#

    21.3±2.93++
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    23.5±2.80**

    20.5±2.40++

    DBP(kPa)

    10.4±0.67

    12.4±1.20**#

    10.7±1.60+

    13.4±1.20**

    11.3±1.73++

    MAP(kPa)

    12.4±1.07
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    18.8±1.87**#

    15.9±2.27++

    16.4±1.47**

    13.9±1.20++

    PRA(ng/ml.h-1)

    1.53±1.03

    0.46±0.23*#

    1.0±0.7++

    0.76±0.51*
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    0.64±0.27

    AII(pg/ml)

    76±23

    33±15*##

    53±31+

    63±37

    58±33

    EDLS(ng/L)

    271±57

    468±93*#

    444±120
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    417±96*

    443±154

    RBC-D(%)

    20.2±7.9

    10.8±1.9*#

    6.3±2.2+

    12.5±2.4*

    6.0±3.1+

    oKos (h-1)

    0.25±0.05
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    0.19±0.03*#

    0.22±0.07+

    0.17±0.02*

    0.20±0.06+

    [Na+]i(mmol/L)

    9.0±1.1

    10.5±1.1

    11.6±3.1

    10.1±1.0

    11.3±1.2
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    *:P<0.05,**:P<0.01 vs control;#:P<0.05, ##:P<0.01 vs NAP;+:P<0.05,++:P<0.01 vs Before treatment

    2.3 治疗前EH组各参数相关性检验

    2.3.1老年EH组中,AII与收缩压、年龄呈负相关(分别r=-0.43,r=-0.49;P<0.05); RBC-D%分别与AII、EDLS、oKos呈负相关(分别r=-0.50; r=-0.40; r=-0.48;P<0.05);PRA与EDLS呈负相关(r=-0.42, P<0.05)。

    2.3.2 非老年EH组SBP、DBP与EDLS呈负相关(分别r=-0.62, P<0.01; r=-0.45, P<0.05), 与PRA、AII、RBC-D%、oKos、[Na+ ]i无相关性。
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    3 讨论


     老年人EH部分为老年起病,部分由老年前期EH病人演进而来,但临床上大都表现为较高的SBP和相对较低的DBP,脉压差随年龄增大,而PRA、AII逐年降低。这显然与老年前期及青中年EH表现不同,提示老年人EH发生机制不同或EH演变过程中影响血压的因素也在演变。本实验显示,老年EH病人血浆EDLS(Ouabain类物,钠泵抑制物)浓度和钠泵活性较非老年EH病人高,而反映EDLS与膜亲和力的指标RBC-D%较低。EDLS仅作用钠泵上洋地黄结合位点,而不作用于其它离子泵[4]。所以,RBC-D%降低可看成是EDLS与膜钠泵亲和力降低。当RBC-D%降低时,为达到一定的EDLS与膜结合量,机体必须分泌更多EDLS。因此,血浆EDLS增加可能是一种代偿反应。老年EH病人RBC-D%较非老年EH病人低,故EDLS分泌更多。老年EH病人在较高的血浆EDLS浓度下,细胞膜钠泵活性并未受到较大抑制,即钠泵活性仍较高,表明在老年EH病人中,一定量EDLS抑制细胞膜钠泵的生物学效应下降,亦即钠泵呈现Ouabain抵抗现象。其原因可能是在老年人EH中,升高的EDLS不足以抵消RBC-D%降低因素,致EDLS与细胞膜钠泵结合量相对较低。非老年EH病人在较老年EH病人低的血浆EDLS浓度下,细胞膜钠泵活性已明显受抑制,不表现Ouabain抵抗现象。
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    本实验显示老年EH病人EDLS与PRA呈负相关。EDLS如抑制肾小管细胞膜钠泵,将产生利尿效应,当钠泵产生Ouabain抵抗,则利尿效应会减弱,有报道钠泵产生Ouabain抵抗后可使肾脏出现排钠障碍[5]。老年人EH因此可发生钠水潴留,反馈抑制体内醛固酮、PRA和AII的产生,故PRA、AII降低。升高的EDLS不仅抑制肾小管细胞膜钠泵,也抑制血管平滑肌细胞膜钠泵,影响细胞内钠、钙离子浓度,升高外周阻力,产生高血压。非老年EH病人EDLS与血压呈负相关,提示非老年EH病人EDLS升高为继发改变。Na+泵有3种α亚单位,各α亚单位对洋地黄糖甙(如Ouabain)敏感性明显不同[6],2组EH病人RBC-D%均降低,但在程度上以及Ouabain抵抗、EDLS和oKos等方面有差别,可能是因Na+泵亚单位不同分子结构或功能改变所致。

    肾小球入球小动脉上的近球细胞内钙离子钙浓度增高可抑制肾素分泌[7]。硝苯啶不仅作用于血管平滑肌细胞,也作用于肾入球小动脉上由平滑肌转化来的近球细胞而影响RAS。细胞内钙离子浓度下降,将通过钠钙交换等影响钠离子浓度,进而影响钠泵活性、EDLS产生[8]。予钙拮抗剂降压治疗后,老年EH病人PRA、AII、oKos明显恢复至正常或接近正常,但EDLS有下降趋势,钠泵对Ouabain抵抗减轻。进一步表明Ouabain抵抗在老年人EH中起重要作用。而老年前期和青中年EH病人PRA、AII无明显变化,EDLS有升高趋势,与老年EH病人表现不同,这可能与两者发病机制不同或老年EH病人对钙拮抗剂更敏感有关[9]。钙拮抗剂可部分纠正这种钠代谢及体液因素异常,提示在老年EH病人中,长期予钙拮抗剂降压治疗不仅对钙代谢同时对钠代谢也是有益处的。
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    *国家自然科学基金资助项目,No.39725013

    作者简介:谭建聪,男,35岁,主治医师,讲师,博士研究生

    参考文献

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    3 Cumberbatch M, Morgan D B. Relations between sodium transport and sodium concentration in human erythrocytes in health and disease. Clin Sci,1981,60(5):555
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    4 Tao Q F, Soszynski D A, Hollenberg N K, et al. A sensitive [Na+,K+] ATPase assay, specific for inhibitors acting via the digitalis-binding site. J Cardiovasc Pharmacol, 1995,25(6):859

    5 Anner B M, Imesch E, Moosmayer M. Sodium transport defect of ouabain-resistant renal Na+,K+-ATPase. Biochem Biophys Res Commun,1989,165(1):360

    6 Tao Q F, Hollenberg N K, Price D A, et al. Sodium pump isoform specificity for the digitalis-like factor isolated from human peritoneal dialysate. Hypertension, 1997,29(3):815
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    7 Haller H. Modulation of endothelial function: Strategy for long-term cardiovascular protection. J Hyprtens, 1996,14(Suppl 4):27

    8 谭建聪,刘光耀,刘晓莉,等. 高血压病患者红细胞钠氢离子交换及钙离子内流的变化. 中华医学杂志, 1993,73(12):759

    9 Hall W D. A rational approach to the treatment of hypertension in special populations. Am Fam Physician,1999,60(1):156

    (收稿:1998-12-11;修回:1999-07-04), 百拇医药