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Figure 5 Changes in the intracytoplasmic Ca2+ concentration ([Ca2+]i) of platelet thrombi caused by adenosine diphosphate receptor antagonists. These experiments were conducted as described in the caption of Figure 3, except that blood was replaced with a cell suspension containing fluo-3AM–loaded platelets, washed erythrocytes, and homologous platelet-poor plasma with the specific thrombin inhibitor argatroban (100 µmol/l) as the anticoagulant. The cell suspension was perfused over type I collagen fibrils at the shear rate of 1,500 s–1 for 4 min to form platelet thrombi. Then, the same cell suspension without or with the addition of the P2Y12 antagonist AR-C69931MX (100 nmol/l), or the P2Y1 antagonist MRS2179 (100 µmol/l), was perfused for an additional 4 min. The [Ca2+]i of platelets incorporated into thrombi was measured during the second perfusion. (Left panels) Intracytoplasmic Ca2+ concentration of five randomly selected platelets recorded for 10 s beginning 2 min after the start of the second perfusion. (Right panels) Images reflecting the concentration of Ca2+ ions in platelets within thrombi formed during perfusion of untreated blood (Control) or blood containing 100 nmol/l AR-C69931MX (ARC).
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