Rajasekhar D, Barnard M R, Bednarek F J, Michelson A D
Department of Pediatrics, University of Massachusetts Medical School, Worcester, USA.
Thromb Haemost. 1997 May;77(5):1002-7.
Very few studies have examined platelet function in very low birth weight (VLBW) preterm neonates, because of the relatively large volumes of blood required. In this study, platelet function in clinically stable VLBW neonates was examined by whole blood flow cytometry, which requires only 5 microliters of whole blood per assay. The following monoclonal antibodies were used: S12 (P-selectin-specific, reflecting alpha granule secretion), PAC1 (directed against the fibrinogen binding site exposed on the GPIIb-IIIa complex of activated platelets), F26 (directed against a conformational change in fibrinogen bound to the GPIIb-IIIa complex), and 6D1 (directed against the von Willebrand factor binding site on the GPIb-IX-V complex). VLBW neonates, like normal adults, did not have circulating activated platelets, as determined by the lack of binding of S12, PAC1, and F26 in the absence of an added agonist. VLBW neonatal platelets were markedly less reactive than adult platelets to thrombin, ADP/epinephrine, and U46619 (a stable thromboxane A2 analogue), as determined by the extent of increase in the platelet binding of S12, PAC1, and F26, and the extent of decrease in the platelet binding of 6D1. In summary, compared to adults, the platelets of VLBW neonates are markedly hyporeactive to thrombin, ADP/epinephrine and a thromboxane A2 analogue in the physiologic milieu of whole blood, as determined by: 1) the increase in platelet surface P-selectin; 2) the exposure of the fibrinogen binding site on the GPIIb-IIIa complex; 3) fibrinogen binding; and 4) the decrease in platelet surface GPIb. This platelet hyporeactivity may be a factor in the propensity of VLBW neonates to intraventricular hemorrhage. In addition to its previously defined use as a test of platelet hyperreactivity, the present study suggests that whole blood flow cytometry may be useful in the clinical assessment of platelet hyporeactivity.
由于所需血量相对较多，很少有研究检测极低出生体重（VLBW）早产儿的血小板功能。在本研究中，通过全血流式细胞术检测临床稳定的VLBW新生儿的血小板功能，每次检测仅需5微升全血。使用了以下单克隆抗体：S12（P-选择素特异性，反映α颗粒分泌）、PAC1（针对活化血小板的糖蛋白IIb-IIIa复合物上暴露的纤维蛋白原结合位点）、F26（针对与糖蛋白IIb-IIIa复合物结合的纤维蛋白原的构象变化）和6D1（针对糖蛋白Ib-IX-V复合物上的血管性血友病因子结合位点）。在未添加激动剂的情况下，通过S12、PAC1和F26缺乏结合来确定，VLBW新生儿与正常成年人一样，没有循环活化血小板。通过S12、PAC1和F26的血小板结合增加程度以及6D1的血小板结合减少程度来确定，VLBW新生儿血小板对凝血酶、ADP/肾上腺素和U46619（一种稳定的血栓素A2类似物）的反应明显低于成人血小板。总之，与成年人相比，在全血的生理环境中，VLBW新生儿的血小板对凝血酶、ADP/肾上腺素和血栓素A2类似物的反应明显低下，这通过以下方面确定：1）血小板表面P-选择素增加；2）糖蛋白IIb-IIIa复合物上纤维蛋白原结合位点暴露；3）纤维蛋白原结合；4）血小板表面糖蛋白Ib减少。这种血小板低反应性可能是VLBW新生儿发生脑室内出血倾向的一个因素。除了其先前定义的作为血小板高反应性检测的用途外，本研究表明全血流式细胞术可能有助于血小板低反应性的临床评估。
