Protection of HDMEC in suspension from apoptosis. HDMEC were incubated for 18 hours while kept in suspension, with various concentrations of VEGF added to the incubation medium. Apoptosis was quantitated by ELISA (in arbitrary units) and viability (expressed as the percentage of viable cells) was measured by dye exclusion. Protection by VEGF became significant at 250 pg/mL and maximal at 2.5 ng/mL. Significance is indicated (*P < .05 and **P < .01) above the brackets for viability measurements and below the brackets for apoptosis measurements.