Kinetics and dose-response of TNF- and VEGF-stimulated soluble tie-1 release in HUVECs. (A) HUVECs were incubated in the absence (□) or presence of 10 ng/mL TNF (•) or 100 ng/mL VEGF (▪) for the indicated times. (B) HUVECs were incubated for 1 hour with the indicated concentrations of TNF (•) or VEGF (▪). After treatment, supernatants were collected and assayed for soluble tie-1 release as described in Materials and Methods. Results are shown as the mean absorbance at 450 nm ± SD.