3.前列环素（prostacyclin，PGI<sub>2</sub>）和血栓素A<sub>2</sub>（thromboxane，TXA<sub>2</sub>）失衡正常内皮细胞可合成PGI<sub>2</sub>，具扩张血管和抑制血小板聚集作用，与促进血小板凝聚的TXA<sub>2</sub>保持动态平衡。
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