Analysis of VEGF₁₆₅ and Sema3A binding to Npn-1. (A) Heparin enhances VEGF₁₆₅ and Sema3A binding to Npn-1. VEGF₁₆₅ (25 ng/mL, ○) or Sema3A (2 μg/mL, □) was added to Npn-1–coated wells with heparin (0-50 000 ng/mL). Bound VEGF₁₆₅ or Sema3A was measured by ELISA. The results reflect the means ± SD of 3 experiments. (B) Analysis of Sema3A binding to Npn-1 in the presence of VEGF₁₆₅. Sema3A (2 μg/mL) was added to Npn-1–coated wells with VEGF₁₆₅ (0-1600 ng/mL) with (○) or without (□) heparin (2 μg/mL). The results reflect the means ± SD of 3 experiments, and are expressed as the mean percent binding of Sema3A in the presence of VEGF₁₆₅ compared with no VEGF₁₆₅.