1. Reduced thrombus stability in mice lacking the α2A-adrenergic receptor
by Miroslava Požgajová, Ulrich J. H. Sachs, Lutz Hein, and Bernhard Nieswandt
Blood
Volume 108(2):
July 15, 2006
©2006 by American Society of Hematology

2. Unaltered platelet responses to thrombin and collagen in α2A–/– mice.
Unaltered platelet responses to thrombin and collagen in α2A–/– mice. (A) Diluted whole blood was incubated with different concentrations of thrombin and CRP, as indicated. Activation of αIIbβ3 and P-selectin expression (not shown) was analyzed by flow cytometry. Results are presented as mean ± SD of 5 mice per group. (B) Heparinized PRP was stimulated with indicated concentrations of fibrillar collagen (“Coll”), and light transmission was recorded on a Fibrintimer 4-channel aggregometer. Results shown are representative of 6 individual experiments. (C) Whole blood was perfused over a “Horm-type” collagen-coated coverslip at high shear (1000 seconds–1). Representative phase-contrast images were taken at the end of the experiment. Images were captured with a Zeiss Axiovert 200 inverted microscope (Carl Zeiss, Jena, Germany) with a 63 ×/0.75 Ph2 objective, a 100-W HBO fluorescent lamp source, and a CCD camera (CV-M300; Visitron Systems, Puchheim, Germany) connected to an AG-7355 S-VHS video camera (Panasonic, Matsushita Electric, Osaka, Japan). Videotaped images were evaluated using a computer-assisted image analysis program, Meta View Version 5.0 (Visitron Systems).
Miroslava Požgajová et al. Blood 2006;108:
©2006 by American Society of Hematology

3. In vitro characterization of α2A–/–-deficient platelets.
In vitro characterization of α2A–/–-deficient platelets. (A) Heparinized PRP was stimulated with ADP (5 μM) and U46619 (1 μM or subthreshold concentration of 0.1 μM) in the presence or absence of 10 μM epinephrine (Epin), and light transmission was recorded on a Fibrintimer 4-channel aggregometer. Results shown are representative of 6 individual experiments. (B) Washed whole blood from wild-type or α2A–/– mice was incubated with 5 μM ADP and 1 μM U46619 (U46) in the presence or absence of 10 μM epinephrine (Epin) for 15 minutes at room temperature. Activation of αIIbβ3 and P-selectin expression was analyzed by flow cytometry. Results are presented as mean ± SD of 5 mice per group.
Miroslava Požgajová et al. Blood 2006;108:
©2006 by American Society of Hematology

4. Highly variable bleeding times and protection from collagen/epinephrine–induced thromboembolism in α2A–/– mice.
Highly variable bleeding times and protection from collagen/epinephrine–induced thromboembolism in α2A–/– mice. (A) Mice were anesthetized, and a 3-mm segment of the tail tip was cut off with a scalpel. Tail bleeding times of wild-type (n = 26) and α2A–/– (n = 31) mice were monitored by gentle absorption of a drop of blood. When no blood was observed on the paper after a 15-second interval, bleeding was determined to have ceased. The experiment was stopped after 20 minutes. Each symbol represents one mouse, and horizontal lines indicate quartiles of bleeding time. (B) Thromboembolic death was observed after the injection of collagen (0.8 mg/kg) and epinephrine (60 μg/kg). All wild-type mice (23 of 23) died, whereas 81.5% (22 of 27) of α2A–/– mice and all mice injected with FcRγ-chain–/– (5 of 5) survived.
Miroslava Požgajová et al. Blood 2006;108:
©2006 by American Society of Hematology

5. Enhanced embolus formation in α2A–/– mice.
Enhanced embolus formation in α2A–/– mice. Thrombosis was induced in mesenteric arteries by topical application of FeCl3. (A) In wild-type mice 95% of formed thrombi were able to occlude, whereas in α2A–/– mice only 55.5% of formed thrombi were able to occlude. Each symbol represents one monitored arteriole, and horizontal lines indicate quartiles of occlusion time. (B) Quantitative analysis of embolus formation in control (1.7 ± 0.32) and mutant (3.1 ± 0.39) mice are presented as the amount of thrombi that detached during the observation period from the viewing field. Results are presented as mean ± SEM. (**P = .01–.05) (C) Representative pictures of 1 experiment are shown for better illustration. Indicated time points represent minutes after FeCl3-induced injury. Images were captured as described in the caption for Figure 1C, except that a 10 ×/0.25 Ph1 objective was used.
Miroslava Požgajová et al. Blood 2006;108:
©2006 by American Society of Hematology

6. Compromised thrombus stability in mice lacking the α2A receptor.
Compromised thrombus stability in mice lacking the α2A receptor. Thrombosis was induced in the aorta by one firm compression with a forceps. Blood flow was monitored with a perivascular ultrasonic flow probe until complete occlusion. The experiment was stopped after 40 minutes. Each symbol represents one mouse, and horizontal lines indicate quartiles of occlusion time.
Miroslava Požgajová et al. Blood 2006;108:
©2006 by American Society of Hematology