Binding of defensin/¹²⁵I-Lp(a) to matrix is heparin sensitive. (A) ¹²⁵I-Lp(a) (10 nmol/L) or a mixture of defensin (2.5 μmol/L) plus ¹²⁵I-Lp(a) (10 nmol/L) or¹²⁵I-defensin (2.5 μmol/L) were incubated with HUVEC matrix in the presence of buffer (□) or heparin (2 U/mL; ▩) for 1 hour at 37°C, and the bound radioactivity was measured. The mean ± SD of 3 experiments is shown. (B) Heparin inhibits the binding of defensin (2.5 μmol/L)/¹²⁵I-Lp(a) (10 nmol/L) complexes to matrix in a dose-dependent manner. The complexes were incubated with HUVEC matrix in the presence of the indicated concentrations of heparin, and the bound radioactivity was measured. Bound radioactivity is expressed relative to the binding of Lp(a) alone. The mean ± SD of 3 experiments is shown.