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磷酸比哆醛抑制血小板凝集作用與血小板形態變化之探討

Anti-aggregative Effects of Pyridoxal-5'-phosphate on Platelet Morphological Changes

摘要


磷酸比哆醛(Pyridoxal-5'-phosphate, PLP)是維生素B6存在於體內的主要活化形式,本研究室先前研究顯示,PLP具有抑制血小板凝集與血液凝固的功能,可能有益於預防心血管疾病。然而,其作用機制與對血小板形態之影響則尚未闡明。本研究利用thrombin,ADP,與collagen等血小板致凝劑誘導富含血小板血漿(platelet rich plasma, PRP)產生凝集現象,使用掃描式電子顯微鏡(SEM)觀察血小板形態變化,並對照可專一性結合表面蛋白GPllb-llla (GP23)的四胜肽血小板凝集抑制劑(Arg-Gly-Asp-Ser, RGDS)的作用,探討PLP對這些致凝劑所誘發的血小板凝集作用的可能機制。結果顯示,thrombin,ADP,collagen對血小板之最強致凝濃度分別為0.5 units/mL,25 μM,0.1 mg/mL。PLP及RGDS對三種致凝物之最強抗凝濃度均分別為1.5 mM與0.23 mM。電子顯微鏡觀察的結果發現,以PLP或RGDS預處理的血小板與致凝物反應後,血小板外觀的變化類似,包括血小板變形現象減少,維持在偽足伸出形態,及較少的凝血蛋白束等。此外,使用thrombin作為致凝物時,以PLP或RGDS處理後的血漿凝血蛋白束均變小,這可能是PLP與RGDS延長血液凝固時間的原因之一。本研究結果顯示PLP可能部分透過與RGDS勝肽抑制血小板凝集的途徑,減少GP23與Fb的結合以抑制血小板凝集。

並列摘要


Pyridoxal-5'-phosphate (PLP), the active form of vitamin B6, was previously studied in our laboratory as a potential anti-aggregative agent which has beneficial effects in preventing cardiovascular diseases. However, the relationship between the anti-aggregative effects and morphological changes of PLP is unclear. In this study, platelet-rich plasma (PRP) was respectively activated by thrombin, ADP, end collagen and co-incubated with the tetrapeptide, Arg-Gly-Asp-Ser (RGDS), or PLP. Morphological changes in platelets were evaluated by scanning electronic microscopy (SEM). The results indicated that optimal aggregative concentrations of thrombin, ADP, and collagen were 0.5 units/mL, 25 μM, and 0.1 mg/mL, respectively. Meanwhile, the optimal anti-aggregative concentrations of PLP and RGDS to those platelet agonists were 1.5 and 0.23 mM, respectively. The SEM data showed that morphological changes in platelet by RGDS or PLP treatment were similar, including lower activation, being sustained in the pseudopod stages, and having smaller fibrin spindles during thrombin induction. The smaller fibrin spindle formation caused by PLP or RGDS might be helpful in preventing blood coagulation. In this study, we provide morphological evidence that the anti-aggregative effect of PLP is partially similar to that of RGDS in inhibiting fibrinogen binding to GP23 receptors.

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