Smith C C, Stanyer L, Cooper M B, Betteridge D J
Department of Medicine, Royal Free and University College Medical School, Sir Jules Thorn Institute, Middlesex Hospital, Mortimer Street, London, UK.
Biochim Biophys Acta. 1999 Dec 27;1473(2-3):286-92. doi: 10.1016/s0304-4165(99)00202-0.
By determining the sum of the supernatant concentrations of nitrite and nitrate the stimulated generation of nitric oxide (NO) by human washed platelets induced by a range of fibrillar collagen concentrations (0.0156-25 microg ml(-1)) was investigated. Platelet serotonin (5-hydroxytryptamine, 5-HT) efflux and platelet aggregation were also measured. Under resting conditions (0 microg ml(-1) collagen) platelet NO release was equivalent to 1.06+/-0.17 nmol per 10(8) platelets. Maximal NO release, equivalent to 2.1+/-0. 37 nmol per 10(8) platelets, was observed with only 0.0625 microg ml(-1) collagen (P<0.02, stimulated vs. resting release), higher collagen concentrations producing no further increases in platelet NO output. By contrast, maximal platelet aggregation and 5-HT efflux did not occur until collagen concentrations of 2.5 microg ml(-1) and 10-25 microg ml-1), respectively, had been achieved. L-NAME (1 mmol l(-1)) and L-NMMA (1 mmol l(-1)) inhibited stimulated platelet NO generation by 78+/-6% and 72%, respectively. Contrasting with fibrillar collagen, fibrillar beta-amyloid protein had no effect on platelet NO generation, or on 5-HT efflux or aggregation. These data perhaps indicate that NO generation by human platelets is stimulated by concentrations of fibrillar collagen insufficient to elicit an aggregatory response. Such a mechanism could operate in vivo to inhibit platelet aggregation which might otherwise be induced by low concentrations of circulating agonists.
通过测定亚硝酸盐和硝酸盐的上清液浓度总和，研究了一系列纤维状胶原蛋白浓度（0.0156 - 25微克/毫升）诱导的人洗涤血小板中一氧化氮（NO）的刺激生成情况。还测量了血小板血清素（5 - 羟色胺，5 - HT）流出和血小板聚集情况。在静息条件下（0微克/毫升胶原蛋白），血小板NO释放量相当于每10⁸个血小板1.06±0.17纳摩尔。仅在0.0625微克/毫升胶原蛋白时观察到最大NO释放量，相当于每10⁸个血小板2.1±0.37纳摩尔（P<0.02，刺激释放与静息释放相比），更高的胶原蛋白浓度未使血小板NO产量进一步增加。相比之下，分别直到胶原蛋白浓度达到2.5微克/毫升和10 - 25微克/毫升时才出现最大血小板聚集和5 - HT流出。L - NAME（1毫摩尔/升）和L - NMMA（1毫摩尔/升）分别抑制刺激的血小板NO生成78±6%和72%。与纤维状胶原蛋白不同，纤维状β - 淀粉样蛋白对血小板NO生成、5 - HT流出或聚集均无影响。这些数据可能表明，人血小板中NO的生成受到不足以引发聚集反应的纤维状胶原蛋白浓度的刺激。这种机制可能在体内发挥作用以抑制血小板聚集，否则血小板聚集可能由低浓度的循环激动剂诱导。
