Steen V M, Holmsen H, Aarbakke G
Department of Biochemistry, University of Bergen, Norway.
Thromb Haemost. 1993 Sep 1;70(3):506-13.
The stimulating effect of adrenaline on human platelet phospholipase C (PLC) activation and responses in vitro (shape change, aggregation and dense granule secretion) was investigated with respect to its dependence on exogenously added agonists. All experiments were performed with human gel-filtered platelets pretreated with acetylsalicylic acid to prevent endogenous stimulation by the arachidonate pathway. (1) Preliminary experiments demonstrated the presence of trace amounts of extracellular ADP (0.05-0.58 microM) in non-stimulated platelet suspensions; ADP was effectively converted to ATP by the enzyme system creatine phosphate (CP)/creatine phosphokinase (CPK). (2) The adrenaline-induced optical aggregation and single particle (platelet) disappearance in the presence of trace amounts of ADP were almost abolished by the ADP-scavenger system CP/CPK. (3) The response of CP/CPK-treated thrombin- or platelet-activating factor (PAF)-stimulated platelets was markedly increased by a subsequent addition of adrenaline. When hirudin or BN 50726 was added just prior to adrenaline to terminate the activation by thrombin or PAF, respectively, the stimulating effect of adrenaline was also abolished. (4) CP/CPK-treated, PAF-stimulated platelets rapidly developed decreased responsiveness to a subsequent addition of PAF. When adrenaline was added instead of a second addition of PAF, the stimulating effect of adrenaline was gradually decreased and prevented in parallel with the homologous desensitization of PAF. (5) The weak platelet agonist serotonin by itself induced only shape change in CP/CPK-treated platelets. Adrenaline failed to enhance the extent of this serotonin-induced platelet activation. (6) These results strongly suggest that adrenaline per se is not a platelet agonist in vitro but acts to enhance the stimulation induced by true agonists.
研究了肾上腺素对人血小板磷脂酶C（PLC）激活及体外反应（形态变化、聚集和致密颗粒分泌）的刺激作用，以及其对外源性添加激动剂的依赖性。所有实验均使用经乙酰水杨酸预处理的人凝胶过滤血小板，以防止花生四烯酸途径的内源性刺激。（1）初步实验表明，未刺激的血小板悬浮液中存在微量细胞外ADP（0.05 - 0.58微摩尔）；ADP可通过磷酸肌酸（CP）/肌酸磷酸激酶（CPK）酶系统有效转化为ATP。（2）在存在微量ADP的情况下，肾上腺素诱导的光学聚集和单个颗粒（血小板）消失几乎被ADP清除系统CP/CPK消除。（3）CP/CPK处理的凝血酶或血小板活化因子（PAF）刺激的血小板，随后添加肾上腺素后，其反应明显增强。当分别在肾上腺素之前加入水蛭素或BN 50726以终止凝血酶或PAF的激活时，肾上腺素的刺激作用也被消除。（4）CP/CPK处理的、PAF刺激的血小板对随后添加的PAF的反应性迅速降低。当加入肾上腺素代替第二次添加PAF时，肾上腺素的刺激作用逐渐降低，并与PAF的同源脱敏同时被阻止。（5）弱血小板激动剂5-羟色胺本身仅在CP/CPK处理的血小板中诱导形态变化。肾上腺素未能增强这种5-羟色胺诱导的血小板激活程度。（6）这些结果强烈表明，肾上腺素本身在体外不是血小板激动剂，而是起到增强真正激动剂诱导的刺激作用。
