Labonté J, Bkaily G, d'Orléans-Juste P
Institute of Pharmacology, Medical School, University of Sherbrooke, Québec, Canada.
J Cardiovasc Pharmacol. 2000 Nov;36(5 Suppl 1):S184-6. doi: 10.1097/00005344-200036051-00056.
An experimental protocol of adenosine diphosphate-(ADP) induced platelet aggregation in the mouse was designed in order to study the roles played by endothelin-A (ET(A)) and endothelin-B (ET(B)) receptors in the ET-1-induced inhibition of ex vivo platelet aggregation. The pressor effects of ET-1 or IRL-1620 were firstly determined in vivo in anesthetized (ketamine/xylazine) CD-1 mice (males and females; 25-30 g). All agents were administered intravenously (via the jugular vein) and blood samples were collected from the carotid artery into heparinized Eppendorfs (15 U/ml). To obtain platelet-rich plasma (PRP) the blood was immediately centrifuged for 12 min at low speed (1100 g). Platelet-poor plasma (PPP) was then prepared by centrifugation of the whole blood sample at high speed (3700 g) for 30 min. PPP was used to calibrate the aggregometer at 100% transmission. Platelet aggregation was monitored ex vivo as a change in light transmission through PRP following the injection of ADP (5 microM). ET-1 (0.01-2.0 nmol/kg) induced a significant and dose-dependent inhibition of platelet aggregation ex vivo (12-84%). The selective ET(B) agonist, IRL-1620 (0.05-2.0 nmol/kg), also triggered a marked inhibition of platelet aggregation. Indomethacin (10 mg/kg), a nonselective cyclooxygenase inhibitor, abolished the inhibitory effect of ET-1. The selective ET(A) antagonist, BQ-123 (1 nmol/kg), abolished the in vivo pressor effect of exogenous ET-1, without affecting its anti-aggregatory activity. The selective ET(B) antagonist, BQ-788 (0.5 nmol/kg), did not modify the elevation of blood pressure produced by the ET-1; however, it did abrogate dose-dependently the inhibitory effect of ET-1 on platelet aggregation. These results suggest that the anti-aggregatory effect of ET-1, in anesthetized CD-1 mice, relies mainly upon the activation of ET(B) receptors. The mechanism whereby ET-1 exerts this effect, is partially indirect and requires at least the production and the release of prostanoids (possibly PGI2) into the blood stream.
为了研究内皮素 -A（ET(A)）和内皮素 -B（ET(B)）受体在ET -1诱导的体外血小板聚集抑制中所起的作用，设计了一项在小鼠中进行二磷酸腺苷（ADP）诱导血小板聚集的实验方案。首先在麻醉（氯胺酮/赛拉嗪）的CD -1小鼠（雄性和雌性；25 - 30克）体内测定ET -1或IRL -1620的升压作用。所有药物均通过静脉（经颈静脉）给药，并从颈动脉采集血样至含肝素的Eppendorf管（15 U/ml）中。为了获得富含血小板血浆（PRP），血液立即以低速（1100 g）离心12分钟。然后通过将全血样本以高速（3700 g）离心30分钟制备贫血小板血浆（PPP）。PPP用于将聚集仪校准为100%透光率。在注射ADP（5 microM）后，通过监测PRP透光率的变化来体外监测血小板聚集。ET -1（0.01 - 2.0 nmol/kg）在体外诱导了显著的剂量依赖性血小板聚集抑制（12 - 84%）。选择性ET(B)激动剂IRL -1620（0.05 - 2.0 nmol/kg）也引发了明显的血小板聚集抑制。非选择性环氧化酶抑制剂吲哚美辛（10 mg/kg）消除了ET -1的抑制作用。选择性ET(A)拮抗剂BQ -123（1 nmol/kg）消除了外源性ET -1的体内升压作用，而不影响其抗聚集活性。选择性ET(B)拮抗剂BQ -788（0.5 nmol/kg）未改变ET -1引起的血压升高；然而，它确实剂量依赖性地消除了ET -1对血小板聚集的抑制作用。这些结果表明，在麻醉的CD -1小鼠中，ET -1的抗聚集作用主要依赖于ET(B)受体的激活。ET -1发挥这种作用的机制部分是间接的，并且至少需要前列腺素（可能是前列环素PGI2）产生并释放到血流中。
