Funder J, Hershco L, Rothstein A, Livne A
Department of Biology, Ben Gurion University of the Negev, Beer Sheva, Israel.
Biochim Biophys Acta. 1988 Mar 3;938(3):425-33. doi: 10.1016/0005-2736(88)90140-x.
Isolated human blood platelets, loaded with the pH-sensitive fluorescence dye 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein show cytoplasmic alkalinization upon stimulation with thrombin but acidification with ADP stimulation. In both cases a Na+/H+ exchange is activated. This can be revealed by the sensitivity of the induced pH changes to amiloride and to 5-N-(3-aminophenyl)amiloride (APA), known inhibitors of the Na+/H+ exchanger, and by a dependence on sodium in the external medium. ADP-induced platelet aggregation is not affected by omission of sodium from the external medium. Furthermore, aggregation is barely inhibited (less than 10%) by amiloride or APA at concentrations up to 50 microM while the Ki values in affecting the Na+/H+ exchange are 5.9 and 1.6 microM for amiloride and APA, respectively. Platelet aggregation is inhibited by amiloride or APA at concentrations higher than 50 microM, but this inhibition is apparently due to a secondary effect of the agents. It is concluded that platelet aggregation induced by ADP is not dependent on activation of Na+/H+ exchange.
分离出的人血血小板，加载了对pH敏感的荧光染料2',7'-双（羧乙基）-5,6-羧基荧光素，在凝血酶刺激下会出现细胞质碱化，但在ADP刺激下会出现酸化。在这两种情况下，Na+/H+交换都会被激活。这可以通过诱导的pH变化对氨氯吡咪和5-N-（3-氨基苯基）氨氯吡咪（APA）（已知的Na+/H+交换抑制剂）的敏感性以及对外部介质中钠的依赖性来揭示。从外部介质中去除钠不会影响ADP诱导的血小板聚集。此外，在浓度高达50 microM时，氨氯吡咪或APA对聚集的抑制作用很小（小于10%），而氨氯吡咪和APA影响Na+/H+交换的Ki值分别为5.9 microM和1.6 microM。在高于50 microM的浓度下，氨氯吡咪或APA会抑制血小板聚集，但这种抑制显然是由于这些药物的次要作用。得出的结论是，ADP诱导的血小板聚集不依赖于Na+/H+交换的激活。
