Specific binding of phospholipid platelet-activating factor by human platelets.
Specific binding of phospholipid platelet-activating factor by human platelets.
复制标题
人血小板与磷脂血小板激活因子的特异性结合。
作者：
F. Valone;E. Coles;V. R. Reinhold;E. Goetzl
磷脂血小板活化因子1-O-十六烷基-2-乙酰基-sn-甘油基-3-磷酸胆碱（AGEPC）与洗涤的人血小板的结合在2分钟内完成80%以上，这与AGEPC引发血小板聚集的时间一致。Scatchard图分析的结合[3 H]AGEPC血小板无和过量的未标记的AGEPC揭示了两种不同类型的结合位点。一个血小板位点对AGEPC表现出高亲和力（KD = 37 +/- 13 nM，平均值+/- SD），是可饱和的，并且具有1399 +/- 498（平均值+/- SD）个AGEPC分子/血小板的低最大容量。其他血小板网站表现出几乎无限的结合能力，与非受体摄取AGEPC进入细胞结构一致。通过比较几种AGEPC类似物抑制[3 H]AGEPC与血小板结合和诱导血小板聚集的能力，评估AGEPC高亲和力结合位点的特异性。醚键在位置1，在位置2的短链脂肪酸，和胆碱部分的极性头基团被证明是至关重要的结合的[3 H]AGEPC血小板和血小板聚集的启动。血小板在37 ℃下暴露于AGEPC 5分钟功能上使暴露的血小板对随后的AGEPC刺激失活，如通过减少的聚集所评估的，并且伴随地降低了[3 H]AGEPC的特异性结合。失活事件的时间过程的评估揭示了在37 ℃下90秒后对AGEPC的聚集响应的损失，尽管保留了高达50%的AGEPC的特异性结合位点。
The binding of the phospholipid platelet-activating factor 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphorylcholine (AGEPC) to washed human platelets was more than 80% complete within 2 min, which coincided with the time of initiation of platelet aggregation by AGEPC. Scatchard plot analysis of the binding of [3H]AGEPC to platelets without and with an excess of unlabeled AGEPC revealed two distinct types of binding sites. One platelet site for AGEPC exhibited a high affinity (KD = 37 +/- 13 nM, mean +/- SD), was saturable, and had a low maximal capacity of 1399 +/- 498 (mean +/- SD) molecules of AGEPC/platelet. The other platelet site demonstrated a nearly infinite binding capacity, consistent with nonreceptor uptake of AGEPC into cellular structures. The specificity of the high-affinity binding site for AGEPC was assessed by comparing the capacity of several analogues of AGEPC to inhibit the binding of [3H]AGEPC to platelets and to induce platelet aggregation. An ether linkage in position 1, a short-chain fatty acid in position 2, and a choline moiety in the polar head group proved to be critical both for the binding of [3H]AGEPC to platelets and for the initiation of platelet aggregation. Exposure of platelets to AGEPC for 5 min at 37 degrees C functionally deactivated the exposed platelets to subsequent stimulation by AGEPC, as assessed by diminished aggregation, and concomitantly reduced the specific binding of [3H]AGEPC. Evaluation of the time course of the events of deactivation revealed the loss of an aggregation response to AGEPC after 90 sec at 37 degrees C, despite the retention of up to 50% of the specific binding sites for AGEPC.