Effects of heparin-binding site mutations on antithrombin antiangiogenic activity. Resting HUVECs were incubated with 20 μg/mL native (N) and cleaved forms (C) of wild-type, K114M, and K125M antithrombins in the presence (▪) and absence (□) of bFGF (10 ng/mL) for 48 hours. Panel A shows the effect of high-affinity glycoforms of the recombinant antithrombins, whereas panel B compares high-affinity with low-affinity glycoforms of the K114M variant (the latter denoted by *). Colorimetric quantification of cell numbers was achieved as described in Figure 2A. Each value represents the mean of 3 experiments ± SD in each of which quadruplicate samples were run.