Brown J A, Jimenez S A, Colman R W
J Lab Clin Med. 1980 Jan;95(1):90-8.
Multimerization of collagen molecules appears to be a prerequisite for collagen-induced platelet aggregation and release. Whether a similar requirement exists for collagen-initiated platelet disc-to-sphere transformation, one of the earliest events in the platelet:collagen interaction, is not known. We have studied platelet shape change by highly purified type I collagen in the presence of EDTA to prevent interference from platelet aggregation and release. The ability of soluble collagen to induce platelet shape change was dependent on prior fibril formation. Tropocollagen from which multimers were removed was not able to initiate the disc-to-sphere transformation, indicating that monomeric collagen is insufficient as a platelet activator. Increasing the extent of multimerization by preincubation at 37 degrees led to an increase in the response rate and a decrease in the lag time for initiation of shape change, but even after maximal multimerization, the lag time was not eliminated. The increase in the turbidity of the collagen solution preceded its ability to stimulate platelet shape change, suggesting that a minimum size of the multimer is needed for platelet activation. L-Arginine, an inhibitor of multimerization, prevented collagen-induced shape change in a dose-dependent relationship. Enhancement of the shape change response rate as a function of the concentration of collagen multimers was found.
胶原蛋白分子的多聚化似乎是胶原蛋白诱导血小板聚集和释放的一个先决条件。对于血小板与胶原蛋白相互作用中最早发生的事件之一——胶原蛋白引发的血小板盘状到球状转变，是否存在类似的要求尚不清楚。我们在存在乙二胺四乙酸（EDTA）的情况下，用高度纯化的I型胶原蛋白研究了血小板形状变化，以防止血小板聚集和释放的干扰。可溶性胶原蛋白诱导血小板形状变化的能力取决于先前的原纤维形成。去除多聚体的原胶原蛋白不能引发盘状到球状的转变，这表明单体胶原蛋白作为血小板激活剂是不足的。通过在37℃预孵育增加多聚化程度导致形状变化起始的反应速率增加和延迟时间减少，但即使在最大程度的多聚化之后，延迟时间也没有消除。胶原蛋白溶液浊度的增加先于其刺激血小板形状变化的能力，这表明血小板激活需要多聚体的最小尺寸。L-精氨酸是一种多聚化抑制剂，它以剂量依赖关系阻止胶原蛋白诱导的形状变化。发现形状变化反应速率随胶原蛋白多聚体浓度的增加而增强。
