Localization/organization of endothelial integrins αvβ3 and α5β1. HUVECs were grown for 3 hours on vitronectin- or fibronectin-coated plates before fixing and staining. β3 and α5 integrin subunits were detected by indirect immunofluorescence and F-actin with fluorescently-conjugated phalloidin. Scale bar represents 20 μm. Results from a representative experiment (of at least 3) are shown.