Figure 3: Lung binding of 125I-VEGF added to the perfusate of isolated perfused rat lungs (IPRL), as determined by counts per minute (CPM) of radioactivity per gram of lung tissue. The final [125I-VEGF] was 1 pM (23 pg/ml), similar to the [VEGF] of platelet supernatants in this study. 125I-VEGF bound avidly to VEGF receptors within the pulmonary vasculature (Vehicle, preincubation of 125I-VEGF with 10 ul of PBS). This binding amounted to 30-40% of added radioactivity and was specific to VEGF receptors as it was potently inhibited by pre-perfusion with a 1000-fold excess concentration of unlabeled (“Cold”) VEGF and was strongly inhibited when 125I-VEGF was pre-incubated with a VEGF antibody (VEGF-Ab in 10 ul of PBS), whereas a control antibody (CMV-Ab in 10 ul of PBS) had no significant effect. Perfusion with 125I-VEGF was done for 15 minutes.* P < 0.0001 by unpaired t-test. Results are depicted as group mean ± SEM