Golino P, Cappelli-Bigazzi M, Ambrosio G, Ragni M, Russolillo E, Condorelli M, Chiariello M
Department of Internal Medicine (Division of Cardiology), 2nd School of Medicine, University of Naples, Italy.
Circ Res. 1992 Dec;71(6):1447-56. doi: 10.1161/01.res.71.6.1447.
It has been shown that endothelium-derived relaxing factor (EDRF) may inhibit platelet aggregation in vitro through activation of platelet-soluble guanylate cyclase. To assess whether EDRF may also affect platelet function in vivo, intravascular platelet aggregation was initiated by placing an external constrictor around endothelially injured rabbit carotid arteries. Carotid blood flow velocity was measured continuously by a Doppler flow probe placed proximal to the constrictor. After placement of the constrictor, cyclic flow reductions (CFRs), due to recurrent platelet aggregation, developed at the site of the stenosis. After CFRs were observed for 30 minutes, a solution of authentic nitric oxide (NO, n = 10) was infused into the carotid artery via a small catheter placed proximally to the stenosis. Before infusion of NO, CFR frequency averaged 18.3 +/- 2.9 cycles per hour, and CFR severity (lowest carotid blood flow as percentage of baseline values) was 6 +/- 1%. NO completely inhibited CFRs in all animals, as shown by the normal and constant pattern of carotid blood flow (CFR frequency, 0 cycles per hour, p < 0.001; carotid blood flow, 92 +/- 5%, p = NS versus baseline). These effects were transient; CFRs were restored spontaneously within 10 minutes after cessation of NO infusion. After CFRs returned, S-nitroso-cysteine (S-NO-cys), a proposed form of EDRF, was infused into the carotid artery. S-NO-cys also abolished CFRs in all animals but at a significantly lower dose than NO (0.3 +/- 0.1 versus 12 +/- 4 nmol/min). The role of endogenously released EDRF in modulating in vivo platelet function was then tested in additional experiments. In 10 animals, endogenous release of EDRF was stimulated by infusing acetylcholine into the aortic root during CFRs. Infusion of acetylcholine was also associated with a complete inhibition of CFRs, similar to that observed during exogenous infusion of NO or S-NO-cys. These antithrombotic effects of acetylcholine were completely lost when EDRF synthesis was prevented by administration of the L-arginine analogue NG-monomethyl L-arginine (L-NMMA). Furthermore, in six additional rabbits the basal release of EDRF was blocked by L-NMMA after CFRs had been previously abolished with aspirin or the combination of aspirin and ketanserin, a serotonin S2 receptor antagonist. L-NMMA caused restoration of CFRs in all animals, indicating that even the basal release of EDRF is important in modulating platelet reactivity in vivo. Taken together, the data of the present study demonstrate that endogenous EDRF might importantly contribute to the modulation of platelet function in vivo.
研究表明，内皮衍生舒张因子（EDRF）可能通过激活血小板可溶性鸟苷酸环化酶在体外抑制血小板聚集。为评估EDRF是否也会在体内影响血小板功能，通过在兔颈总动脉内皮损伤处放置外部收缩器来引发血管内血小板聚集。使用置于收缩器近端的多普勒血流探头连续测量颈总动脉血流速度。放置收缩器后，由于反复的血小板聚集，在狭窄部位出现周期性血流减少（CFR）。观察到CFR 30分钟后，通过置于狭窄部位近端的小导管将真实一氧化氮（NO，n = 10）溶液注入颈总动脉。在注入NO之前，CFR频率平均为每小时18.3±2.9次循环，CFR严重程度（最低颈总动脉血流占基线值的百分比）为6±1%。如颈总动脉血流正常且恒定的模式所示（CFR频率，每小时0次循环，p < 0.001；颈总动脉血流，92±5%，与基线相比p = NS），NO完全抑制了所有动物的CFR。这些作用是短暂的；在停止注入NO后10分钟内CFR自发恢复。CFR恢复后，将一种推测的EDRF形式S-亚硝基半胱氨酸（S-NO-cys）注入颈总动脉。S-NO-cys也消除了所有动物的CFR，但所需剂量明显低于NO（0.3±0.1对12±4 nmol/分钟）。然后在另外的实验中测试内源性释放的EDRF在调节体内血小板功能中的作用。在10只动物中，在CFR期间通过向主动脉根部注入乙酰胆碱来刺激EDRF的内源性释放。注入乙酰胆碱也与CFR的完全抑制相关，类似于在外源性注入NO或S-NO-cys期间观察到的情况。当通过给予L-精氨酸类似物NG-单甲基-L-精氨酸（L-NMMA）阻止EDRF合成时，乙酰胆碱的这些抗血栓形成作用完全丧失。此外，在另外6只兔子中，在用阿司匹林或阿司匹林与5-羟色胺S2受体拮抗剂酮色林联合用药预先消除CFR后，L-NMMA阻断了EDRF的基础释放。L-NMMA使所有动物的CFR恢复，表明即使是EDRF的基础释放对调节体内血小板反应性也很重要。综上所述，本研究数据表明内源性EDRF可能在体内对血小板功能的调节中起重要作用。
