溶血磷脂酸激活大鼠血小板L-精氨酸/一氧化氮通路

目的:观察溶血磷脂酸(LPA)对血小板L-精氨酸/一氧化氮合酶/一氧化氮(L-Arg/NOS/NO)通路的影响,并探讨其与血小板功能变化的关系.方法:LPA(10-6,10-5和5×10-5 mol/L)与大鼠血小板混悬液共孵育,采用Greiss法测定血小板孵育液中亚硝酸盐(NO-2)含量;同位素示踪法检测血小板NOS活性及L-Arg转运;荧光探针法测定血小板内游离钙浓度.结果:LPA孵育30和60 min, 血小板NO释放分别增加了35%和56%(P＜0.01),LPA(10-6,10-5和5×10-5 mol/L)呈浓度依赖性增加了血小板NO的生成,EC50为17.8 μmol/L,95%CI为13.1～24.2 μmol/L(P＜0.01).LPA浓度依赖性增加了 NOS活性和血小板L-Arg的转运(P＜0.01).LPA(5×10-5 mol/L)孵育30和60 min,显著升高血小板Ca2 ]i水平(P＜0.01).NOS抑制剂L-NAME预处理的血小板,LPA升高Ca2 ]i的反应分别增强20%和32%(P＜0.01);加入NO供体L-Arg预处理,则明显抑制LPA升高Ca2 ]i,分别减少14%和18%(P＜0.01).结论:LPA通过激活血小板L-Arg转运和NOS活性,上调L-Arg/NOS/NO通路,增加血小板NO生成.

Lysophosphatidic acid activates L-arginine/nitric oxide pathway of platelets in rats

OBJECTIVE: To investigate the mechanism of platelet function caused by Lysophosphatidic acid (LPA), by observing the change of the L-arginine/nitric oxide synthase/nitric oxide (L-Arg/NOS/NO) pathway of platelet in rats. METHODS: LPA (10(-6), 10(-5) and 5x10(-5) mol/L) was administrated in rats and incubated for 30 and 60 minutes. The nitrite production was measured by Greiss assay; NOS activities and L-arginine transportation were detected by isotope tracer method and intracellular Ca(2+)]i changes by fluorescent probe. RESULTS: LPA increased NO release by 35% and 56%, after incubating for 30 and 60 minutes, respectively. LPA (10(-6), 10(-5)aand 5x10(-5) mol/L) enhanced the NO productions of platelets in a concentration-dependent manner (P<0.01). EC(50) was 17.8 micromol/L, and 95% CI was 13.3-24.2 micromol/L, involved in the physiological concentration of LPA in plasma (P<0.01). Simultaneously, different doses of LPA increased NOS activities and L-arginine uptake in a dose-dependent manner (P<0.01). In this study, LPA (50 micromol/L) increased the intracellular free calcium ion concentration (Ca(2+)]i, P<0.01), after incubating for 30 and 60 minutes. Pre-treated with NOS inhibitor-L-NAME for 20 minutes, LPA obviously enhanced the effects by 20% and 32% respectively (P<0.01). On the contrary, pre-treated with L-arginine (200 micromol/L) for the same times obviously reduced the effects by 14% and 18% respectively (P<0.01). CONCLUSION: LPA increased NO release by enhancing L-arginine uptake and NOS activities, up-regulating L-arginine/NOS/NO pathway in platelets of rats.