HUVEC spreading on matrix glycoproteins. Cell morphology on coverslips coated with PLL, vitronectin, or collagen IV (50 μg/mL) was examined. Cells were treated for 4 hours with RGDS (500 μg/mL) and stained with FITC-conjugated phalloidin (original magnification, × 40). In all cases cells showed a similar spreading and actin stress fibers morphology, indicating that while RGDS had no antiadhesive effect on collagen IV and poly-_L-lysine, it had an antiadhesive effect on vitronectin, as expected. Experiments were carried out in triplicate. The images shown refer to a representative experiment.