The chemokines SDF-1 and MDC enhance platelet adhesion to collagen and fibrinogen under high-shear flow conditions.

Washed platelets were pumped through a continuous-flow adhesion system^18;20 and mixed with SDF-1 and MDC (0.5 μg/mL) just before they entered the adhesion column, which provided a contact (adhesion) time of 0.67 seconds. The beads in the adhesion column were coated with either basement-membrane type IV collagen (A) or with fibrinogen (B). As described in the “Materials and methods,” adhesion to collagen was studied in a Mg²⁺-based medium and that to fibrinogen was studied in a Ca²⁺/Mg²⁺-based medium, all in the absence of added soluble fibrinogen. In some of the experiments, the platelets were exposed to apyrase for 10 minutes at 37°C before they were pumped through the column. Results are expressed as means ± SEM from 3 donors and represent the percentage of platelets adhering to the beads. The significance of the decreases in platelet adhesion caused by apyrase is *P < .02, **P < .01, and ***P < .001.