Nishikawa M, Hidaka H, Shirakawa S
Department of Internal Medicine, Mie University School of Medicine, Japan.
Biochem Pharmacol. 1988 Aug 15;37(16):3079-89. doi: 10.1016/0006-2952(88)90304-8.
Arachidonate and other unsaturated fatty acids stimulated platelet protein kinase C in a dose-dependent manner (5-50 micrograms/ml), when the activity was assayed with either isolated substrates or the platelet cytosol. When human platelets were stimulated by arachidonate, two types of platelet activation were observed. Platelet activation induced by a low level of arachidonate (0.1-5 micrograms/ml) was inhibited by aspirin, but activation induced by a high level of arachidonate (10-50 micrograms/ml) was not. These activations were associated with the phosphorylation of 40K and 20K proteins. Other unsaturated fatty acids (10-50 micrograms/ml) also induced platelet aggregation which was not inhibited by aspirin. Arachidic acid and methyl arachidonate, which did not stimulate protein kinase C, also did not induce platelet responses. Although a low level of arachidonate (0.45 microgram/ml) induced the rapid and transient formation of [3H]-1,2-diacylglycerol and [32P]phosphatidate in intact platelets with [3H]arachidonate or [32P]Pi, unsaturated fatty acids at a high concentration (50 micrograms/ml) did not stimulate phospholipase C. Incubation of fura 2 loaded platelets with a high level of unsaturated fatty acids evoked a rise in cytosolic Ca2+-concentration ([Ca2+]i) but this [Ca2+]i elevation alone was not associated with platelet activation. These results suggest that a high level of unsaturated fatty acids induces platelet activation, without phospholipase C stimulation, and that the ability of unsaturated fatty acid to directly activate protein kinase C may contribute toward the activation of platelets by a high level of unsaturated fatty acid.
当用分离的底物或血小板胞质溶胶测定活性时，花生四烯酸和其他不饱和脂肪酸以剂量依赖方式（5 - 50微克/毫升）刺激血小板蛋白激酶C。当用花生四烯酸刺激人血小板时，观察到两种类型的血小板活化。低水平花生四烯酸（0.1 - 5微克/毫升）诱导的血小板活化被阿司匹林抑制，但高水平花生四烯酸（10 - 50微克/毫升）诱导的活化则未被抑制。这些活化与40K和20K蛋白的磷酸化有关。其他不饱和脂肪酸（10 - 50微克/毫升）也诱导血小板聚集，且不受阿司匹林抑制。不刺激蛋白激酶C的花生酸和花生酸甲酯也不诱导血小板反应。尽管低水平的花生四烯酸（0.45微克/毫升）用[3H]花生四烯酸或[32P]Pi在完整血小板中诱导[3H]-1,2 - 二酰甘油和[32P]磷脂酸的快速和短暂形成，但高浓度（50微克/毫升）的不饱和脂肪酸不刺激磷脂酶C。用高水平不饱和脂肪酸孵育负载fura 2的血小板会引起胞质Ca2 +浓度（[Ca2 +]i）升高，但仅这种[Ca2 +]i升高与血小板活化无关。这些结果表明，高水平的不饱和脂肪酸在不刺激磷脂酶C的情况下诱导血小板活化，并且不饱和脂肪酸直接激活蛋白激酶C的能力可能有助于高水平不饱和脂肪酸对血小板的活化作用。
