Hargreaves P G, Jenner S, Merritt J E, Sage S O, Farndale R W
Department of Biochemistry, University of Cambridge, UK.
Thromb Haemost. 1996 Aug;76(2):248-52.
Collagen (10-90 micrograms/ml) and ionomycin (1 microM; a calcium ionophore) each evoked rises in intracellular free calcium, protein kinase C activity and arachidonic acid release in human platelets, and as previously demonstrated for collagen, ionomycin (1 microM) stimulated protein tyrosine phosphorylation. However, at lower concentrations (60 and 250 nM) ionomycin selectively mobilised calcium. Ro31-8220 (a selective inhibitor of protein kinase C) inhibited (by 50%) ionomycin-stimulated arachidonic acid release. Genistein (an inhibitor of protein tyrosine kinases) also reduced by 50% ionomycin-stimulated arachidonic acid release. In combination, genistein and Ro31-8220 abolished ionomycin-stimulated arachidonic acid release. These findings show 1) that a rise in calcium is not sufficient, and 2) the activation of both protein kinase C and protein tyrosine phosphorylation is necessary, for full ionomycin-stimulated arachidonic acid release in human platelets.
胶原蛋白（10 - 90微克/毫升）和离子霉素（1微摩尔；一种钙离子载体）均可引起人血小板内游离钙升高、蛋白激酶C活性增强以及花生四烯酸释放，并且正如先前针对胶原蛋白所证明的那样，离子霉素（1微摩尔）可刺激蛋白酪氨酸磷酸化。然而，在较低浓度（60和250纳摩尔）下，离子霉素选择性地动员了钙离子。Ro31 - 8220（一种蛋白激酶C的选择性抑制剂）抑制（50%）了离子霉素刺激的花生四烯酸释放。染料木黄酮（一种蛋白酪氨酸激酶抑制剂）也使离子霉素刺激的花生四烯酸释放减少了50%。染料木黄酮和Ro31 - 8220联合使用时，消除了离子霉素刺激的花生四烯酸释放。这些发现表明：1）钙离子升高并不充分；2）蛋白激酶C的激活和蛋白酪氨酸磷酸化对于离子霉素充分刺激人血小板释放花生四烯酸都是必需的。
