PECAM-1 cross-linking inhibits the mobilization of calcium from intracellular stores.
Fura-2 am–loaded human platelets were stimulated with either Cvx or thrombin, and the mobilization of calcium was measured fluorometrically as described in “Materials and methods” (arrow indicates the addition of agonist). (A) Treatment of platelets with control IgG and cross-linker F(ab′)2 has no effect on Cvx- and thrombin-stimulated calcium mobilization. (B) (i, ii) Representative calcium responses for stimulation with Cvx at 62.5 ng/mL and 15 ng/mL, respectively, with and without first cross-linking PECAM-1. Traces are representative of 3 separate experiments. (iii) PECAM-1–induced percentage reduction in peak levels of intracellular calcium stimulated by 62.5, 31.25, and 15 ng/mL Cvx. Data represent mean ± SE (n = 3). C (i, ii) Representative calcium responses for stimulation with thrombin at 0.1 U/mL and 0.05 U/mL, respectively, with and without first cross-linking PECAM-1. Traces are representative of 3 separate experiments. (iii) PECAM-1–induced percentage reduction in peak levels of intracellular calcium stimulated by 0.5, 0.1, and 0.05 U/mL thrombin. Data represent mean ± SE (n = 3). PECAM-1 XL, PECAM-1 cross-linking.
