Inhibition of bFGF-induced endothelial cell proliferation by cleaved and latent antithrombins. Resting HUVEC cells were cultured in the absence or presence of 10 μg/mL each of native, cleaved, or latent forms of antithrombin both in the absence and presence of 10 ng/mL bFGF as indicated. The number of viable cells was determined after 72 hours of incubation as described in “Materials and methods.” Mean values ± SD (bars) derived from 5 independent determinations are shown. *A statistically significant difference from the control (P < .001) based on a Student t test.