Effect of homocysteine on the l-arginine/nitric oxide synthase/nitric oxide pathway in human platelets

Recent evidence indicates that chronic hyperhomocysteinemia is an independent risk factor for the development of atherosclerosis, thrombosis, and other cardiovascular diseases. This may be secondary to impaired fibrinolysis, or increased platelet reactivity. l-Arginine/nitric oxide synthase/nitric oxide (NO) plays an important role in the regulation of platelet function. The present study was undertaken to determine the effect of homocysteine (HCY) on the l-arginine/NO pathway of human platelets. Washed human platelets were incubated in the presence or absence of HCY for 2 h at 37°C followed by a measurement of indices of the l-arginine/NO pathway. HCY caused a concentration-dependent reduction in the platelet up-take of l-[³H]arginine. HCY also caused a concentration-dependent decrease in nitrite production concurrent with a decrease in cyclic guanosine monophosphate, whereas NO synthase activity of the platelets, measured as conversion of l-[³H]arginine to l-[³H]citrulline, remained unchanged on incubation with HCY. These observations indicate that the l-arginine/NO pathway is involved in the mechanism responsible for the effects of HCY on platelets by diminishing NO production through decreased uptake of l-arginine. Received: June 14, 2001 / Accepted: September 28, 2001     

Pressure natriuresis in rats during blockade of the L-arginine/nitric oxide pathway.

The natriuretic response was studied in anesthetized rats during the intravenous infusion of L-arginine analogues to inhibit the production of endothelium-derived nitric oxide. In an initial experimental series, rats were administered saline vehicle or vehicle containing 300 mumol/kg body wt N omega-monomethyl-L-arginine, N omega-nitro-L-arginine methyl ester, N omega-monomethyl-D-arginine, or L-arginine. Infusion of the competitive inhibitors N omega-monomethyl-L-arginine and N omega-nitro-L-arginine methyl ester significantly increased mean arterial pressure to 155 +/- 3 and 145 +/- 5 mm Hg, respectively, compared with a mean arterial pressure of 118 +/- 3 mm Hg determined in the vehicle control group. Sodium excretion averaged 3.27 +/- 1.08 and 2.52 +/- 0.78 mu eq/min in the N omega-monomethyl-L-arginine- and N omega-nitro-L-arginine methyl ester-treated rats, respectively, and each was significantly higher than the basal sodium excretion of 0.20 +/- 0.05 mu eq/min in the vehicle-treated control animals. Plasma renin activity was significantly lower in the N omega-monomethyl-L-arginine- and N omega-nitro-L-arginine methyl ester-treated groups than in the vehicle-treated group. Neither L-arginine nor N omega-monomethyl-D-arginine administration significantly altered any of the measured variables compared with vehicle alone. In a second experimental series, an adjustable snare was placed around the suprarenal aorta for the purpose of controlling renal perfusion pressure independently of increases in the systemic mean arterial pressure initiated by infusion of N omega-nitro-L-arginine methyl ester (75 mumol/kg i.v.).(ABSTRACT TRUNCATED AT 250 WORDS)     

血小板左旋精氨酸/一氧化氮系统在2型糖尿病胰岛素抵抗中的意义

近来研究表明 ,左旋精氨酸 (Ｌ Ａｒｇ) /一氧化氮 (ＮＯ)系统与胰岛素抵抗 (ＩＲ)有关。血小板是胰岛素的作用部位之一 ,膜上有一氧化氮合酶 (ＮＯＳ)和转运Ｌ Ａｒｇ的通道。本研究测定 2型糖尿病 (ＤＭ)患者血小板ＮＯ含量并观察Ｌ Ａｒｇ和胰岛素孵育对血小板产生ＮＯ的影响 ,以探讨血小板Ｌ Ａｒｇ/ＮＯ系统在ＩＲ中的意义。一、对象和方法1.对象 :正常对照 (ＮＣ)组 13例 (男 7,女 6 ) ,年龄 (5 8±11)岁 ,为体检正常者 ,体重指数 (ＢＭＩ) <2 5ｋｇ/ｍ2 ,〔(2 1.6±0 .8)ｋｇ/ｍ2 〕 ,空腹血糖 (ＦＢＧ) (5 .0 8± 0 .5 1)ｍｍｏｌ/…     

Response of nitric oxide pathway to L-arginine infusion at the altitude of 4,350 m.

It was hypothesized that hypoxia may inhibit nitric oxide (NO) production by reducing the availability of endothelial NO synthase (NOS III) substrate. To evaluate the effect of L-arginine on the NO release in high altitude, 11 subjects were infused with L-arginine (0.5 g x kg(-1)) during 30 min in normoxia and after 36 h at 4,350 m (hypoxia). The L-citrulline and cyclic guanosine monophosphate (cGMP) concentrations were measured to investigate NO synthesis and guanylyl cyclase activity respectively. L-citrulline concentration, arterial oxygen saturation (Sa,O2), systemic blood pressure, heart rate and acute mountain sickness (AMS) score were measured at rest and 15, 30 and 45 min after starting infusion. The results showed that baseline L-citrulline was lower in hypoxia (p<0.05). L-arginine infusion increased L-citrulline concentration in both conditions. However, in hypoxia L-citrulline concentration remained lower than in normoxia (p<0.05). The concentration of cGMP was lower in hypoxia (p<0.05). In hypoxia, Sa,O2 increased from 15 min after the start of the infusion to 45 min (p<0.05). Blood pressure and heart rate were not affected by L-arginine infusion. Subjects who experienced symptoms of AMS showed a slight decrease in AMS score with L-arginine. The decreased L-citrulline suggests a hypoxia-induced impairment of nitric oxide synthase III or a decrease in L-arginine availability. The improvement of arterial oxygen saturation by pretreatment with L-arginine could be ascribed to an enhancement of the ventilation/perfusion ratio. Collectively, these results are consistent with a decrease in nitric oxide production in hypoxia that could be antagonized by supplying nitric oxide synthase cosubstrate.     

动脉粥样硬化家兔主动脉壁与红细胞L-精氨酸/一氧化氮系统变化

目的 观察动脉粥样硬化时主动脉与循环中红细胞L－精氨酸（L－Arg）／一氧化氮（ＮＯ）系统变化的关系。方法 建立动脉粥样硬化模型，喂养家兔１２只，分为动脉粥样硬化组（ＡＳ组）和对照组，分别喂以高脂饮食和普通饮食，６周后取静脉血，并处死动物，测定主动脉和循环中红细胞Ｌ－Ａrg转运，一氧化氮合酶（ＮＯＳ）活性及一氧化氮生成量。结果 动脉粥样硬化主动脉平滑肌细胞Ｌ－Ａrg/NOS/NO系统活性增强，而其内皮细胞ＮＯＳ活性降低；循环中红细胞Ｌ－Ａrg的跨膜转运速率和亲和力降低，其ＮＯＳ活性下降。结论 循环中红细胞Ｌ－Ａrg／ＮＯ系统变化可能是动脉粥样硬化的表现之一，其有可能成为动脉粥样硬化发生发展的检测指标。     

Analysis of nitric oxide-sensitive guanylyl cyclase in human platelets before and after aggregation

Nitric oxide (NO) inhibits platelet adhesion to vascular endothelium and platelet aggregation through activation of soluble guanylyl cyclase (sGC) and a consequent increase in cGMP. The aim of the present study was to analyze NO-sensitive sGC in human platelets before and after aggregation. NO-sensitive sGC activity was tested in the cytosol and membrane fractions of native human platelets and ADP-induced platelet aggregates in the presence of 3?mM Mn²⁺ as cofactor. After ADP-induced platelet aggregation there was a significant increase of sGC activity in membranes. Western blot analysis showed a partial translocation of the enzyme to the plasma membrane. These findings support recent data that sGC is associated with cellular membranes in various tissues and cell types and that this membrane association is influenced by the activation state in human platelets (Nat Cell Biol 2002; 4: 307–11). Using 3?mM Mg²⁺ instead of Mn²⁺ as cofactor, a sharp decrease of sGC activity was apparent in the cytosol of aggregated platelets. Kinetic analysis of the cytosolic enzyme and concentration–response curves for free Mg²⁺ showed that platelet aggregation changes binding of free Mg²⁺ but not binding of the substrate complex Mg·GTP. This effect was specific for free Mg²⁺ and was not seen for free Mn²⁺. In addition, changes in free Mg²⁺ concentration in a physiological range markedly influenced NO-stimulated sGC activity. This provides a possible explanation for the increased platelet aggregability in patients with low intraplatelet Mg²⁺ levels.     

Testosterone modulates platelet aggregation and endothelial cell growth through nitric oxide pathway

The aim of the present study was to investigate the effect of testosterone on the modulation of cellular events associated with vascular homeostasis. In rat aortic strips, 5-20 min treatment with physiological concentrations of testosterone significantly increased nitric oxide (NO) production. The rapid action of the steroid was suppressed by the presence of an androgen receptor antagonist (flutamide). We obtained evidence that the enhancement in NO synthesis was dependent on the influx of calcium from extracellular medium, because in the presence of a calcium channel blocker (verapamil) the effect of testosterone was reduced. Using endothelial cell (EC) cultures, we demonstrated that androgen directly acts at the endothelial level. Chelerythrine or PD98059 compound completely suppressed the increase in NO production, suggesting that the mechanism of action of the steroid involves protein kinase C and mitogen-activated protein kinase pathways. It is known that endothelial NO released into the vascular lumen serves as an inhibitor of platelet activation and aggregation. We showed that testosterone inhibited platelet aggregation and this effect was dependent on endothelial NO synthesis. Indeed, the enhancement of NO production elicited by androgen was associated with EC growth. The steroid significantly increased DNA synthesis after 24 h of treatment, and this mitogenic action was blunted in the presence of NO synthase inhibitor N-nitro-l-arginine methyl ester. In summary, testosterone modulates vascular EC growth and platelet aggregation through its direct action on endothelial NO production.     

Analysis of nitric oxide-sensitive guanylyl cyclase in human platelets before and after aggregation

Nitric oxide (NO) inhibits cell adhesion to vascular endothelium and platelet aggregation through activation of soluble guanylyl cyclase (sGC) and a consequent increase in cGMP. The aim of the present study was to analyze NO-sensitive sGC in human platelets before and after aggregation. NO-sensitive sGC activity was tested in the cytosol and membrane fractions of native human platelets and ADP-induced platelet aggregates in the presence of 3 mM Mn2+ as cofactor. After ADP-induced platelet aggregation there was a significant increase of sGC activity in membranes. Western blot analysis showed a partial translocation of the enzyme to the plasma membrane. These findings support recent data that sGC is associated with cellular membranes in various tissues and cell types and that this membrane association is influenced by the activation state in human platelets (Nat Cell Biol 2002; 4: 307-11). Using 3 mM Mg2+ instead of Mn2+ as cofactor, a sharp decrease of sGC activity was apparent in the cytosol of aggregated platelets. Kinetic analysis of the cytosolic enzyme and concentration-response curves for free Mg2+ showed that platelet aggregation changes binding of free Mg2+ but not binding of the substrate complex Mg.GTP. This effect was specific for free Mg2+ and was not seen for Mn2+. In addition, changes in free Mg2+ concentration in a physiological range markedly influenced NO-stimulated sGC activity. This provides a possible explanation for the increased platelet aggregability in patients with low intraplatelet Mg2+ levels.     

eNOS/NO 信号通路与心血管疾病关系的研究进展

一氧化氮（nitric oxide,NO）作为一种信号分子,在生理活动中起着重要作用,包括血压调节、血管张力维持、免疫系统调控等,尤其在心血管系统中发挥重要作用。NO产生异常是多种心血管疾病的诱因。内皮型一氧化氮合酶（endothelial nitric oxide synthase,eNOS）作为诱导合成NO的限速酶,主要在血管壁的调节中发挥重要作用,因此,其与心血管的正常生理活动密切相关。本文综述了eNOS的基本结构与功能、NO的理化性质,以及eNOS/NO信号通路与心血管系统疾病的关系。     

Reversal by L-arginine of a dysfunctional arginine/nitric oxide pathway in the endothelium of the genetic diabetic BB rat

Summary We examined the effects of acute supplementation with arginine in vitro on endothelium-dependent relaxation in aortic rings taken from female genetic, diabetes-prone BB rats. Sensitivity to norepinephrine-induced contraction was unaltered in rings of diabetic BB rats compared to rings from non-diabetic littermates. In precontracted rings, acetylcholine produced a concentration-dependent relaxation which was impaired by diabetes. This relaxation was blocked by l-nitroarginine in both control and diabetic rings. Addition of 3 mmol/l l-arginine (but not d-arginine) enhanced relaxation in diabetic rings similar to that seen in control rings without arginine. l-arginine had no effect on acetylcholine-induced relaxation in control rings. In contrast, relaxation-induced by nitroglycerin in diabetic rings without endothelium was not altered by l-arginine treatment. Thus, a defect in the utilization of arginine by nitric oxide synthase exists in the endothelium of the diabetic BB rat. [Diabetologia (1997) 40: 910–915] Received: 24 February 1997 and in revised form: 17 April 1997     

beta(2)-adrenoceptors activate nitric oxide synthase in human platelets

Nitric oxide (NO), generated by platelets through stimulation of nitric oxide synthase (NOS), limits platelet adhesion and aggregation after a prothrombotic stimulus. Platelet beta-adrenoceptors (betaARs) mediate inhibition of aggregation, but no direct link has been shown between these receptors and platelet adhesion or NO production. We examined NOS activity in human platelets from the conversion of L-[(3)H]-arginine to L-[(3)H]-citrulline, after betaAR stimulation or cAMP elevation. Basal NOS activity was 0.11+/-0.03 pmol L-citrulline/10(8) platelets. The betaAR agonist isoproterenol 1 micromol/L and the adenylyl cyclase activator forskolin 1 micromol/L each increased NOS activity, to 0.26+/-0.04 and 0.23+/-0.03 pmol L-citrulline/10(8) platelets, respectively (P<0.01 for each). Both responses were abolished by the adenylyl cyclase inhibitor SQ22536 50 micromol/L. NOS activation by isoproterenol or forskolin was not associated with a change in intracellular Ca(2+). In functional studies, isoproterenol inhibited U46619-induced platelet aggregation in a concentration-dependent manner, but this effect was not significantly diminished by NOS inhibition. In contrast, thrombin-stimulated platelet adhesion to cultured human umbilical vein endothelial cell monolayers was inhibited by isoproterenol, and this effect was abolished by NOS inhibition (1.3+/-0.2% versus 2.6+/-0.2% respectively; P<0.001). Effects of isoproterenol on NOS activity, platelet aggregation, and adhesion were mediated exclusively through beta(2)ARs, as determined by coincubation with betaAR subtype-selective antagonists. We conclude that beta(2)ARs activate platelet NOS by increasing cAMP, and that this activation is Ca(2+)-independent. beta(2)ARs may contribute to modulation of platelet aggregation and adhesion to endothelium, and our findings suggest that activation of the L-arginine/NO system mediates the effects of beta(2)ARs on adhesion but not aggregation.     

醛固酮对血管外膜诱导型一氧化氮合酶/一氧化氮通路影响的实验研究

目的观察醛固酮对血管外膜诱导型一氧化氮合酶（iNOS）／一氧化氮（NO）通路的影响及作用机制。方法取sD大鼠胸主动脉外膜,分别给予不同浓度醛固酮（ALD）10^-8～10^-6mol／L、ALl）＋螺内酯以及ALD＋RU486进行孵育,此外在给予脂多糖激活血管外膜iNOS／NO的情况下,观察以上各组药物刺激后iNOS／NO系统的变化。与上述药物共同孵育6h后通过Griess法测定相对稳定的代谢产物硝酸盐和亚硝酸盐（NOx）代表NO的产生量,采用[^3H]-L-精氨酸标记的同位素法测定外膜iNOS活性。结果（1）NOx产生的变化：ALD刺激后血管外膜NOx生成无明显变化。用螺内酯拮抗盐皮质激素受体后,高浓度ALD组（10～～10^-6mol／L）血管外膜NOx产生呈下降趋势（P〈0．05）。用RU486拮抗糖皮质激素受体后随ALD浓度增加NOx生成量也呈浓度依赖性增加（P〈0．01）。脂多糖刺激后上述趋势更为明显。（2）iNOS活性的变化：ALD刺激后iNOS活性无明显变化,螺内酯刺激后血管外膜iNOS活性有下降趋势,但无统计学意义。而RU486刺激后血管外膜iNOS活性显著增加（P〈0．05）。同时给予脂多糖刺激后,螺内酯＋ALD组血管外膜iNOS活性显著下降（P〈0．01）,ALD＋RU486组血管外膜iNOS活性显著增加（p〈0．05）。结论ALD主要通过盐皮质激素受体和糖皮质激素受体通路两种途径直接影响血管外膜iNOS／NO系统,醛固酮作用于盐皮质激素受体能够诱导iNOS激活、刺激NO产生,作用于糖皮质激素受体抑制iNOS／NO激活。     

In vivo aspirin supplementation inhibits nitric oxide consumption by human platelets

Antiplatelet therapies improve endothelial function in atherosclerosis, suggesting that platelets regulate vascular nitric oxide (NO) bioactivity in vivo. Herein, washed platelets consumed NO on activation in an aspirin-sensitive manner, and aspirin enhanced platelet NO responses in vitro. To examine whether in vivo aspirin can inhibit platelet NO consumption, a double-blind placebo-controlled study was conducted. After a 2-week nonsteroidal anti-inflammatory drug (NSAID)-free period, healthy men were randomly assigned and administered aspirin (75 mg/d orally) or identical placebo for 14 days, then crossed over to the opposite arm. Following in vivo aspirin, NO consumption by platelets was inhibited 91%. Rate of onset and recovery following aspirin withdrawal was consistent with cyclooxygenase 1 (COX-1) inhibition. In a small substudy, NO consumption by platelets from postmenopausal women was faster in hypercholesterolemics and less sensitive to aspirin (ie, 39% versus 76% inhibition for hypercholesterolemics or normocholesterolemics, respectively). However, 150 mg aspirin/day increased inhibition of NO consumption by platelets of hypercholesterolemics to 80%. Comparisons of platelet COX-1 or -2 expression and urinary 11-dehydro-thromboxane B2 excretion suggested that aspirin was less able to block platelet activation in vivo in hypercholesterolemia. In conclusion, aspirin inhibits NO consumption by platelets from healthy subjects, but its beneficial effects on NO bioactivity may be compromised in some hypercholesterolemic patients.     

L-arginine availability is not limiting for nitric oxide generation from recombinant endothelial nitric oxide synthase

L-arginine (L-Arg) may be limiting for inducible nitric oxide synthase (NOS) activity and under certain circumstances, such as increased concentrations of a NOS inhibitor, may also be limiting for endothelial NOS activity. It is unknown if L-Arg is limiting for recombinant eNOS activity in the vascular wall after adenoviral mediated gene transfer. Our aim was to examine, if L-Arg is limiting for recombinant eNOS activity in the normal or atherosclerotic vessel wall. Rings of rabbit aorta from chow or cholesterol fed animals were transduced with adenovirus vector encoding eNOS (AdeNOS) or beta-galactosidase (AdbetaGal). After 24 h, transgene expression was confirmed and vasomotor studies were performed in the absence or presence of L-Arg. During maximal contractions to phenylephrine (10(-5) M), L-Arg (3 mM) was added to the organ chamber for 30 min. Subsequently, relaxations to acetylcholine during half-maximal contractions were obtained. In the chow- and cholesterol-fed animals, relaxations were significantly enhanced in the NOS and NOS + L-Arg groups compared to the betaGal and betaGal + L-Arg groups. There was no difference between NOS and NOS + L-Arg or betaGal and betaGal + L-Arg rings from chow- or cholesterol-fed animals. While gene transfer of eNOS enhances endothelium-dependent vasorelaxation in the normal and atherosclerotic vessel wall, L-arginine is not limiting for recombinant eNOS activity.     

The nitric oxide/cGMP signaling pathway in pulmonary hypertension

This article briefly reviews the background of endothelium-dependent vasorelaxation, describes the nitric oxide/cGMP/protein kinase pathway and its role in modulating pulmonary vascular tone and remodeling, and describes three approaches that target the nitric oxide/cGMP pathway in the treatment of patients with pulmonary arterial hypertension.     

Effect of systemic L-arginine administration on hemodynamics and nitric oxide release in man.

The effects of L-arginine administration on systemic hemodynamics and plasma concentrations of neuro-endocrine hormones and amino acids were investigated in 10 normotensive healthy volunteers. Nitrite/nitrate in urine and cyclic guanosine monophosphate (c-GMP) in plasma were also measured as indicators of release of nitric oxide (NO). L-arginine administration (30 g/300 ml/30 min) caused hypotension (mean arterial pressure; 79.3 +/- 3.9 mmHg fell to 68.8 +/- 2.2 mmHg) with tachycardia (62.3 +/- 2.3 beats/min increased to 67.5 +/- 1.9 beats/min). The plasma concentration of L-arginine before administration was 98.8 +/- 8.2 mumol/l and increased to 7263 +/- 567 mumol/l 20 min after administration. Cardiac output also increased to 127.2 +/- 3.9% by L-arginine administration. Total peripheral resistance was calculated to fall to 65.9 +/- 2.0%. L-arginine administration slightly changed several hormones, but all values were within normal ranges. Nitrite/nitrate in urine increased 142.1 +/- 12.4% compared to the values before L-arginine administration. Plasma concentrations of c-GMP and L-citrulline, the by-product of NO from L-arginine, were also significantly increased by L-arginine administration. All our results provide evidence for the first time that systemically administered L-arginine releases NO in man.     

Effects of L-arginine in rat adrenal cells: involvement of nitric oxide synthase.

The effects of L-arginine on corticosterone production, cGMP, and nitrite levels were examined in zona fasciculata adrenal cells. L-Arginine significantly decreased both basal and ACTH-stimulated corticosterone production. This effect was still evident when steroidogenesis was induced by 8-bromo-cAMP and 22(R)-hydroxycholesterol, but not in the presence of exogenously added pregnenolone. L-Arginine increased cGMP and nitrite levels,; these effects were blocked by the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl-ester. Transport of L-[3H]arginine was rapid, saturable, and monophasic, with an apparent Km of 163+/-14 microM and a maximum velocity of 53+/-6 pmol/min x 10(5) cells. The basic amino acids L-lysine and L-ornithine, but not D-arginine or the nitric oxide synthase inhibitors N(G)-nitro-L-arginine methyl-ester and N(G)-nitro-L-arginine, impaired L-arginine uptake. Taken together, these results suggest that steroidogenesis in zona fasciculata adrenal cells may be negatively modulated by L-arginine-derived nitric oxide.     

Oxidation of nitric oxide in aqueous solution to nitrite but not nitrate: comparison with enzymatically formed nitric oxide from L-arginine.

Nitric oxide (NO) in oxygen-containing aqueous solution has a short half-life that is often attributed to a rapid oxidation to both NO2- and NO3-. The chemical fate of NO in aqueous solution is often assumed to be the same as that in air, where NO is oxidized to NO2 followed by dimerization to N2O4. Water then reacts with N2O4 to form both NO2- and NO3-. We report here that NO in aqueous solution containing oxygen is oxidized primarily to NO2- with little or no formation of NO3-. In the presence of oxyhemoglobin or oxymyoglobin, however, NO and NO2- were oxidized completely to NO3-. Methemoglobin was inactive in this regard. The unpurified cytosolic fraction from rat cerebellum, which contains constitutive NO synthase activity, catalyzed the conversion of L-arginine primarily to NO3- (NO2-/NO3- ratio = 0.25). After chromatography on DEAE-Sephacel or affinity chromatography using 2',5'-ADP-Sepharose 4B, active fractions containing NO synthase activity catalyzed the conversion of L-arginine primarily to NO2- (NO2-/NO3- ratio = 5.6) or only to NO2-, respectively. Unpurified cytosol from activated rat alveolar macrophages catalyzed the conversion of L-arginine to NO2- without formation of NO3-. Addition of 30 microM oxyhemoglobin to all enzyme reaction mixtures resulted in the formation primarily of NO3- (NO2-/NO3- ratio = 0.09 to 0.20). Cyanide ion, which displaces NO2- from its binding sites on oxyhemoglobin, inhibited the formation of NO3-, thereby allowing NO2- to accumulate. These observations indicate clearly that the primary decomposition product of NO in aerobic aqueous solution is NO2- and that further oxidation to NO3- requires the presence of additional oxidizing species such as oxyhemoproteins.     

同型半胱氨酸对正常人血小板L-精氨酸/一氧化氮途径的影响

目的通过观察同型半胱氨酸（Ｈｃｙ）对血小板Ｌ精氨酸（ＬＡｒｇ）／一氧化氮（ＮＯ）系统的影响,探讨Ｈｃｙ对血小板损伤的机制。方法健康成人６例,平均年龄（３３±７）岁。晨取静脉血,将每例血样分为对照组及加Ｈｃｙ组,分别测定血小板ＬＡｒｇ转运功能;同时将上述两组分别设立加乙酰胆碱（Ａｃｈ）与不加Ａｃｈ组,测定血小板ＮＯ合酶（ＮＯＳ）活性、ＮＯ生成量和ｃＧＭＰ含量。结果（１）在不同浓度的Ｌ－Ａｒｇ时,Ｈｃｙ组ＬＡｒｇ转运速率均低于对照组（Ｐ＜００１）。（２）在Ａｃｈ刺激下,ＮＯＳ活性明显提高,但Ｈｃｙ组提高的程度明显低于对照组（Ｐ＜００１）。（３）在Ａｃｈ刺激下,ＮＯ生成及ｃＧＭＰ含量明显提高（Ｐ＜００１）,但Ｈｃｙ组仍明显低于对照组（Ｐ＜００５）。结论Ｈｃｙ影响血小板功能可能与ＬＡｒｇ／ＮＯ系统改变有关。