Immunofluorescence microscopy (IF) shows the effect of thrombin and EDTA, and inhibitors of EC contraction on actin and ICGF. Actin was stained with rhodamine-labeled phalloidin. The camera shutter speed was set automatically so the intensities are not relative. These representative photos show that thrombin- but not EDTA-induced ICGF was blocked by the inhibitor, bromo-cAMP, and that both were blocked by the cross-linker, glutaraldehyde. HUVEC in the photos were (A) untreated; (B) thrombin-stimulated; (C) EDTA-treated; (D) incubated with bromo-cAMP before treating with control buffer; (E) incubated with bromo-cAMP before treating with thrombin; (F) incubated with bromo-cAMP before treating with EDTA; (G) incubated with glutaraldehyde before treating with control buffer; (H) incubated with glutaraldehyde before treating with thrombin; and (I) incubated with glutaraldehyde before treating with EDTA.