Kundu N, Kornhauser R
Department of Biological Sciences, Ohio University, Athens 45701.
Life Sci. 1993;53(26):1967-74. doi: 10.1016/0024-3205(93)90018-x.
This study was conducted to determine the mechanisms of increased platelet reactivity to thrombin in hypertension. Thrombin induced significantly greater platelet aggregation in spontaneously hypertensive (SHR) than in normotensive (Wistar Kyoto, WKY) rats. Fibrinogen and thrombin binding to platelets was determined using [125I]-fibrinogen and [125I]-thrombin respectively. Increased platelet aggregation in SHR correlated with thrombin-induced greater binding of fibrinogen to SHR than to WKY platelets. However, the number of thrombin receptors (binding sites/platelet) in WKY (19,500 +/- 3,000) and SHR (23,100 +/- 3,000) as well as thrombin dissociation constants were statistically similar in WKY (1.17 +/- 0.2 microM) and SHR (1.62 +/- 0.27 microM) platelets. Fura 2/AM, a fluorescent calcium indicator, loaded platelets were used to quantify the platelet ionized calcium ([Ca2+]i). The [Ca2+]i in unstimulated SHR and WKY platelets was essentially the same. In a calcium poor medium, thrombin-induced a 35% greater increase in [Ca2+]i in SHR than in WKY platelets. These data, taken together with our earlier observations that thrombin induces a significantly greater hydrolysis of phosphoinositide (Thromb. Res. 49, 5-21, 1988), lead us to suggest that thrombin-induced increased generation of inositol 1,4,5-trisphosphate and diacylglycerol induces greater fibrinogen binding and consequently increased aggregation in SHR than WKY platelets. The finding that the thrombin binding isotherms are similar in WKY and SHR platelets suggests that increased platelet sensitivity to thrombin in hypertension may be due to altered signal transduction and not due to changes in the number or affinity of thrombin receptors.
本研究旨在确定高血压患者血小板对凝血酶反应性增加的机制。凝血酶诱导自发性高血压（SHR）大鼠的血小板聚集显著高于正常血压（Wistar Kyoto，WKY）大鼠。分别使用[125I] - 纤维蛋白原和[125I] - 凝血酶测定纤维蛋白原和凝血酶与血小板的结合。SHR中血小板聚集增加与凝血酶诱导的纤维蛋白原与SHR血小板的结合比WKY血小板更多相关。然而，WKY（19,500±3,000）和SHR（23,100±3,000）中凝血酶受体的数量（结合位点/血小板）以及WKY（1.17±0.2 microM）和SHR（1.62±0.27 microM）血小板中的凝血酶解离常数在统计学上相似。使用Fura 2/AM（一种荧光钙指示剂）负载的血小板来定量血小板游离钙（[Ca2 + ]i）。未刺激的SHR和WKY血小板中的[Ca2 + ]i基本相同。在缺钙培养基中，凝血酶诱导SHR血小板中[Ca2 + ]i的增加比WKY血小板高35％。这些数据，连同我们早期的观察结果，即凝血酶诱导磷酸肌醇的水解显著增加（血栓形成研究。49,5 - 21,1988），使我们提出凝血酶诱导的肌醇1,4,5 - 三磷酸和二酰基甘油生成增加诱导了比WKY血小板更大的纤维蛋白原结合，从而导致SHR中聚集增加。WKY和SHR血小板中凝血酶结合等温线相似的发现表明，高血压中血小板对凝血酶的敏感性增加可能是由于信号转导改变，而不是由于凝血酶受体数量或亲和力的变化。
