Greenberg J, Packham M A, Cazenave J P, Reimers H J, Mustard J F
Lab Invest. 1975 Apr;32(4):476-84.
A number of investigators have implicated sialic acid on the surface of platelets in platelet function. In this study we have quantitated the amount of sialic acid removed by purified neuraminidase from the surface of washed platelets of man, rabbit, or pig and examined the effects of this removal. Purified neuraminidase did not induce the release of platelet granule contents. Platelets were pre-labeled with 14C-serotonin for measurement of the release reaction or with 51Cr for determination of adherence to a collagen-coated surface or damaged aortic surface, and for in vivo platelet survival studies. Washed, neuraminidase-treated platelets were resuspended in Tyrode's solution containing 0.35 per cent albumin or in citrated platelet-free plasma from the same species. Both resuspending fluids contained apyrase. Aggregating agents tested were ADP, acid-soluble collagen, thrombin, ristocetin (with human platelets), polylysine, and serotonin (with rabbit platelets). With all of these agents except polylysine, aggregation of neuraminidase-treated human or rabbit platelets was slightly enhanced compared with control platelets; aggregation of pig platelets was unchanged. When release-inducing agents were used, neuraminidase-treated platelets released more of their 14C-serotonin than control platelets. The extent to which rabbit platelets adhered to a collagen-coated surface or to the damaged surface of everted rabbit aorta was unchanged by pretreatment of platelets with neuraminidase. Therefore it seems unlikely that sialic acid is involved in platelet adherence to collagen. When more than 15 per cent of total sialic acid had been removed from rabbit platelets, they were completely cleared from the circulation within 1 hour of their injection into rabbits. When 8 to 10 per cent of total sialic acid had been removed, the platelets were not cleared immediately from the circulation but were cleared more quickly than control platelets. Thus, although removal of up to 65 per cent of platelet sialic acid has only a slightly enhancing effect on platelet aggregation and release in vitro, removal of as little as 8 to 10 per cent results in the recognition of platelets as "foreign" in vivo.
许多研究者认为血小板表面的唾液酸与血小板功能有关。在本研究中，我们定量了纯化的神经氨酸酶从人、兔或猪的洗涤血小板表面去除的唾液酸量，并研究了这种去除的影响。纯化的神经氨酸酶未诱导血小板颗粒内容物的释放。血小板预先用14C-血清素标记以测量释放反应，或用51Cr标记以测定对胶原包被表面或受损主动脉表面的黏附，以及用于体内血小板存活研究。洗涤过的、经神经氨酸酶处理的血小板重悬于含0.35%白蛋白的台氏液中或来自同一物种的枸橼酸化无血小板血浆中。两种重悬液均含有腺苷三磷酸双磷酸酶。测试的聚集剂有二磷酸腺苷（ADP）、酸溶性胶原、凝血酶、瑞斯托霉素（用于人血小板）、聚赖氨酸和血清素（用于兔血小板）。除聚赖氨酸外，与对照血小板相比，经神经氨酸酶处理的人或兔血小板与所有这些试剂的聚集均略有增强；猪血小板的聚集未改变。当使用诱导释放的试剂时，经神经氨酸酶处理的血小板比对照血小板释放更多的14C-血清素。用神经氨酸酶预处理血小板后，兔血小板对胶原包被表面或外翻兔主动脉受损表面的黏附程度未改变。因此，唾液酸似乎不太可能参与血小板与胶原的黏附。当兔血小板总唾液酸的15%以上被去除时，将它们注入兔体内后1小时内便从循环中完全清除。当总唾液酸的8%至10%被去除时，血小板不会立即从循环中清除，但比对照血小板清除得更快。因此，尽管去除高达65%的血小板唾液酸对体外血小板聚集和释放仅有轻微增强作用，但仅去除8%至10%就会导致血小板在体内被识别为“外来物”。
