Hechler B, Eckly A, Ohlmann P, Cazenave J P, Gachet C
INSERM U.311, ETSS, Strasbourg, France.
Br J Haematol. 1998 Dec;103(3):858-66. doi: 10.1046/j.1365-2141.1998.01056.x.
Recently we showed that the P2Y1 receptor coupled to calcium mobilization is necessary to initiate ADP-induced human platelet aggregation. Since the thienopyridine compound clopidogrel specifically inhibits ADP-induced platelet aggregation, it was of interest to determine whether the P2Y1 receptor was the target of this drug. Therefore we studied the effects of clopidogrel and of the two specific P2Y1 antagonists A2P5P and A3P5P on ADP-induced platelet events in rats. Although clopidogrel treatment (50 mg/kg) greatly reduced platelet aggregation in response to ADP as compared to untreated platelets, some residual aggregation was still detectable. In contrast, A2P5P and A3P5P totally abolished ADP-induced shape change and aggregation in platelets from both control and clopidogrel-treated rats. A2P5P and A3P5P (100 microM) totally inhibited the [Ca2+]i rise induced by ADP (0.1 microM) in control and clopidogrel-treated platelets, whereas clopidogrel treatment had no effect. Conversely, the inhibition of adenylyl cyclase induced by ADP (5 microM) was completely blocked by clopidogrel but not modified by A2P5P or A3P5P (100 microM). A3P5P (1 mM) reduced the number of [33P]2MeSADP binding sites on control rat platelets from 907 +/- 50 to 611 +/- 25 per platelet. After clopidogrel treatment, binding of [33P]2MeSADP decreased to 505 +/- 68 sites per platelet and further decreased to 55 +/- 12 sites in the presence of A3P5P (1 mM). In summary, these results demonstrate that the platelet P2Y1 receptor responsible for the initiation of aggregation in response to ADP is not the target of clopidogrel. Platelets may express another, as yet unidentified, P2Y receptor, specifically coupled to the inhibition of adenylyl cyclase and necessary to induce full platelet aggregation, which could be the target of this drug.
最近我们发现，与钙动员偶联的P2Y1受体对于启动ADP诱导的人血小板聚集是必需的。由于噻吩并吡啶化合物氯吡格雷可特异性抑制ADP诱导的血小板聚集，因此确定P2Y1受体是否为该药物的作用靶点很有意义。因此，我们研究了氯吡格雷以及两种特异性P2Y1拮抗剂A2P5P和A3P5P对大鼠ADP诱导的血小板事件的影响。与未处理的血小板相比，尽管氯吡格雷处理（50 mg/kg）可显著降低血小板对ADP的聚集反应，但仍可检测到一些残余聚集。相反，A2P5P和A3P5P可完全消除对照组和氯吡格雷处理组大鼠血小板中ADP诱导的形态变化和聚集。A2P5P和A3P5P（100 microM）可完全抑制对照组和氯吡格雷处理组血小板中由ADP（0.1 microM）诱导的[Ca2+]i升高，而氯吡格雷处理则无此作用。相反，氯吡格雷可完全阻断ADP（5 microM）诱导的腺苷酸环化酶抑制作用，而A2P5P或A3P5P（100 microM）则无此作用。A3P5P（1 mM）可使对照组大鼠血小板上[33P]2MeSADP结合位点的数量从每个血小板907±50个减少至611±25个。氯吡格雷处理后，[33P]2MeSADP的结合量降至每个血小板505±68个位点，在存在A3P5P（1 mM）时进一步降至55±12个位点。总之，这些结果表明，负责启动对ADP聚集反应的血小板P2Y1受体不是氯吡格雷的作用靶点。血小板可能表达另一种尚未确定的P2Y受体，该受体特异性偶联至腺苷酸环化酶的抑制作用，并且对于诱导完全的血小板聚集是必需的，它可能是该药物的作用靶点。
