Effects of antibodies against u-PA, t-PA, and u-PAR and of addition of single chain u-PA on hormone-modulated tube formation. hMVEC were cultured on three-dimensional fibrin matrices in incubation medium containing 20 ng/mL bFGF and 20 ng/mL TNF-α, and the appropriate hormone. Activity blocking antibodies to u-PA, t-PA, and u-PAR were added at the start of an experiment, whereas single chain u-PA was added from day 2 onward. After 8 to 11 days, the total length of capillary-like tubular structures was determined as described in Materials and Methods. (A) Effect of solvent (PBS), antibodies to u-PA (α uPA, 150 μg/mL) or t-PA (α tPA, 150 μg/mL) and rabbit IgG isolated from pooled normal serum (con-ab, 150 μg/mL) on tube formation of hMVEC in incubation medium supplemented with vehicle (con, 0.01% (vol/vol) DMSO) or all-trans retinoic acid (RA, 1 μmol/L). (B) Effect of solvent (PBS), antibody to u-PAR (α uPAR, 25 μg/mL) and antibody to FITC (con-ab, 25 μg/mL) on tube formation of hMVEC in incubation medium supplemented with vehicle (con, 0.01% DMSO) or all-trans retinoic acid (RA, 1 μmol/L). (C) Effect of addition of solvent (PBS) and scu-PA (10 or 30 ng scu-PA) on tube formation of hMVEC in incubation medium supplemented with vehicle (con, 0.01% DMSO), testosterone (test, 1 μmol/L), or dexamethasone (dex, 1 μmol/L). The data represent the average of two experiments performed in duplicate wells (with ranges given by error bars) and are expressed as percentages of control values (tube-length/cm² in the presence of bFGF and TNF-α).