Pharmacology and Molecular Biology Research Laboratories, Sankyo Co. Ltd, 1-2 58 Hiromachi, Shinagawa-ku, Tokyo 140, Japan.
Platelets. 1995;6(6):388-93. doi: 10.3109/09537109509078477.
We previously reported that thrombin-induced Ca(2+) mobilization was enhanced in aged rat platelets. Since Ca(2+) mobilization in platelets is believed to be closely associated with platelet activation, we examined Ca(2+) mobilization and the aggregatory response to ADP and thrombin in young (3 months) and aged (24 months) rat platelets. Blood levels of fibrinogen and Ca(2+) in aged rats were higher than those in young rats. ADP-induced platelet aggregation in aged rats was significantly enhanced in platelet rich plasma and in washed platelet suspension, suggesting that age-associated hyperaggregability to ADP is attributable to changes in platelets themselves. On the other hand, thrombin (0.03-0.3 unit/ml)-induced aggregation in washed platelet suspension from aged rats was comparable to that from young rats. But, thrombin (0.3 unit/ml)-induced intracellular Ca(2+)mobilization was enhanced in aged rat platelets in the presence of extracellular Ca(2+). Likewise, ADP-induced Ca(2+) mobilization was enhanced in aged rat platelets. These results suggest that enhanced Ca(2+) mobilization in aged rat platelets is associated with hyperaggregability to ADP but not to thrombin.
我们之前曾报道过，在老年大鼠的血小板中，凝血酶诱导的 Ca(2+)动员增强。由于血小板中的 Ca(2+)动员被认为与血小板激活密切相关，我们研究了年轻（3 个月）和老年（24 个月）大鼠血小板对 ADP 和凝血酶的 Ca(2+)动员和聚集反应。老年大鼠的血纤维蛋白原和 Ca(2+)水平高于年轻大鼠。富含血小板的血浆和洗涤血小板悬浮液中的 ADP 诱导的血小板聚集在老年大鼠中明显增强，表明与年龄相关的 ADP 高聚集性归因于血小板本身的变化。另一方面，在洗涤血小板悬浮液中，来自老年大鼠的凝血酶（0.03-0.3 单位/ml）诱导的聚集与来自年轻大鼠的聚集相当。但是，在存在细胞外 Ca(2+)的情况下，来自老年大鼠的血小板中凝血酶（0.3 单位/ml）诱导的细胞内 Ca(2+)动员增强。同样，ADP 诱导的 Ca(2+)动员在老年大鼠的血小板中增强。这些结果表明，老年大鼠血小板中增强的 Ca(2+)动员与对 ADP 的高聚集性有关，而与凝血酶无关。
