Yun J C, Ohman K P, Gill J R, Keiser H
Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC 20059.
Can J Physiol Pharmacol. 1991 May;69(5):599-604. doi: 10.1139/y91-088.
The effects of U46619, a thromboxane mimic, on cytosolic Ca2+ concentration and platelet aggregation were determined in human platelets. Cytosolic Ca2+ concentration was determined by Quin-2 fluorescence and platelet aggregation quantitated with an aggregometer. Addition of U46619 (1 x 10(-7) M) to the platelet suspension produced a rapid increase in cytosolic Ca2+ and platelet aggregation. Pretreatment of platelets with EGTA (3 x 10(-3) M), verapamil (5 x 10(-4) M), a calcium entry blocker, or 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (1 x 10(-3) M), an inhibitor of intracellular Ca2+ release, either blunted or markedly delayed the rate, but not the magnitude, of increase in cytosolic Ca2+ and prevented platelet aggregation by U46619. Pretreatment of platelets with prostaglandin I2 (PGI2) (5 x 10(-8) M), PGD2 (5 x 10(-8) M), PGE1 (5 x 10(-8) M), PGF2 alpha (1 x 10(-5) M), dibutyryl cAMP (5 x 10(-3) M), or forskolin (1 x 10(-6) M) prevented both the increase in cytosolic Ca2+ and the associated platelet aggregation induced by U46619. These data suggest that U46619 may induce platelet aggregation through an increase in cytosolic Ca2+, and that both Ca2+ entry and its release from intracellular storage sites probably contribute to the increase in cytosolic Ca2+. Furthermore, the rate of the increase in cytosolic Ca2+ concentration, as well as the magnitude of the increase, appear to be critical for platelet aggregation induced by U46619. Our data are consistent with the hypothesis that PGs inhibit U46619-induced platelet aggregation by preventing the increase in cytosolic Ca2+, and that these effects may be mediated via an increase in cAMP, since they were induced by PGs and cAMP.
在人血小板中测定了血栓素类似物U46619对胞浆Ca2+浓度和血小板聚集的影响。通过喹啉-2荧光法测定胞浆Ca2+浓度，并用血小板聚集仪定量检测血小板聚集情况。向血小板悬液中加入U46619（1×10(-7)M）可使胞浆Ca2+迅速升高并导致血小板聚集。用EGTA（3×10(-3)M）、维拉帕米（5×10(-4)M，一种钙通道阻滞剂）或盐酸8-(二乙氨基)辛基-3,4,5-三甲氧基苯甲酸酯（1×10(-3)M，一种细胞内Ca2+释放抑制剂）预处理血小板，可减弱或显著延迟胞浆Ca2+升高的速率，但不影响其升高幅度，并可阻止U46619诱导的血小板聚集。用前列腺素I2（PGI2）（5×10(-8)M）、PGD2（5×10(-8)M）、PGE1（5×10(-8)M）、PGF2α（1×10(-5)M）、二丁酰cAMP（5×10(-3)M）或福斯可林（1×10(-6)M）预处理血小板，可阻止U46619诱导的胞浆Ca2+升高及相关的血小板聚集。这些数据表明，U46619可能通过升高胞浆Ca2+诱导血小板聚集，并且Ca2+内流及其从细胞内储存部位的释放可能都有助于胞浆Ca2+的升高。此外，胞浆Ca2+浓度升高的速率以及升高幅度似乎对U46619诱导的血小板聚集至关重要。我们的数据与以下假设一致，即前列腺素通过阻止胞浆Ca2+升高来抑制U46619诱导的血小板聚集，并且这些作用可能通过cAMP升高介导，因为它们是由前列腺素和cAMP诱导的。
