Effect of 8-pCPT-cAMP on the lateral motility of integrins and CD44 on the cell surface of EPC. (A,B) EPCs in suspension (in the absence of integrin ligands) were stimulated with 8-pCPT-2′-O-Me-cAMP (100 μM) or PBS (control) for 15 minutes. Then EPCs were fixed in suspension and subsequently were mounted on poly-L-lysine-coated slides. Immunofluorescence was performed for the β2-integrin-subunit CD18 (red fluorescence) (A) or the β1-integrin-subunit CD29 (red fluorescence) (B) and CD44 (green fluorescence), and the stained cells were viewed by confocal microscopy. Micrographs were acquired with an LSM 510 confocal microscope (Zeiss, Jena, Germany) fitted with a Plan-Neofluar 40×/1.3 NA oil objective and LSM 5 image acquisition software (Zeiss). (C) For detection of an activation-dependent epitope on β1-integrins, EPCs were incubated for 15 minutes at 37°C with PE-conjugated HUTS21 antibody or isotype PE-labeled control antibody in the presence of 8-pCPT-2′-O-Me-cAMP (100 μM) or PBS (control) (n = 8, *P < .05 vs control). (D) For detection of the β1-integrin subunits, EPCs were incubated for 15 minutes at room temperature with FITC-conjugated CD29 antibody or an isotype control FITC-labeled antibody in the presence of 8-pCPT-2′-O-Me-cAMP (100 μM) or PBS (control) (n = 3). Error bars represent SEM.