富含EPA浓缩鱼油抑制血小板聚集的机理探讨

流行病学和实验室资料均提示富含EPA鱼油(简称鱼油)具有抑制血小板聚集和抗血栓形成的作用。本文主要探讨鱼油抑制血小板聚集的机理。实验分别将大鼠和家兔随机分成4组:正常组、高脂组、鱼油组、橄榄油组。按各自不同饲料喂养3个月以后,4组大鼠血浆TXB_2/6-酮-PGF_(1a)比值分别为1.4,2.2,1.0,1.7。鱼油组血小板内cAMP含量明显高于高脂组(P<0.05)。鱼油组血清总胆固醇值、血浆TXB_2、5-羟色胺(5-HT)、钙离子浓度、纤维蛋白原含量及血液粘度(低切)均明显低于高脂组(P<0.05)。鱼油组血浆、血小板、心肌及肝脏中EPA、DHA含量明显高于其它3组(P<0.001)。以上结果提示,鱼油抑制血小板聚集和血栓形成的机理可能是,鱼油中的EPA和DHA等高不饱和脂肪酸纳入细胞膜后竞争抑制花生四烯酸(AA)代谢,减少血小板TXA_2生成和释放,降低血中TXA_2/PGI_2比值,同时增加血小板内cAMP含量,稳定血小板功能,减少5-HT,钙离子等具有促聚活性物质释放。另外,鱼油降低血脂、血浆纤维蛋白原含量及血液粘度,从而改善血液流变性,使血小板本身及其周围环境得以改善,防止血小板聚集和血栓形成。

A TENTATIVE STUDY ON THE MECHANISM OF INHIBITION OF PLATELET AGGREGATION BY FISH OIL RICH IN EPA

The mechanism of decreasing platelet aggregation by fish oil rich in n-3 fatty acids was studied in rabbits and rats. These animals were randomly divided into four groups. In rats, group Ⅰ was fed a basal diet; group Ⅱ was fed a high fat diet containing 7.5% lard, 0.25% bile salts, 0.5% cholesterol, group Ⅲ and Ⅳ received the diet with 5% lard, 0.25% bile salts,0.5% cholesterol and 0.5 ml fish oil or 0.5ml olive oil respectively. In rabbits, group Ⅰ was fed a basal diet; group Ⅱ received 20g diets containing 10.4% lard, 2.5% cholesterol, then, some basal diet; group Ⅲ and Ⅳ received 20g diets with 4.2% lard, 2.5% cholesterol and 2 ml fish oil or olive oil respectively, then, some basal diet. Fish oil contained 20% EPA and 50% DHAThree months later, plasma TXB2/6KPGF1α ratios were 1.4, 2.2, 1.0, 1.7. Plasma TXB2, cholesterol, serotonin, calcium, fibrinogen and blood viscosity were significantly lowered in group Ⅲ as compared with group Ⅱ. Platelet cAMP was greatly increased in group Ⅲ than that in group Ⅱ n-3 fatty acids in platelet, plasma and tissues such as liver and heart were definitively higher in group Ⅲ.These experiments showed that fish oil inhibited platelet aggregation and thrombosis formation as a consequence of changing the fatty acids composition in tissue membrane and decreasing TXA2/PGI2 ratio which may stimulate platelat cAMP synthesis and then decrease some agglutinating factors such as serotonin and calcium etc, released from platelet. On the other hand fish oil lowered blood cholesterol, which may change blood cell membrane fluidity, lowered blood fibrinogen and viscosity, so the situation of blood platelet and its surroundings could be improved.