Radiolabeled DT binding inhibition by the recombinant mature Hu and Mk HB-EGF proteins. The specific bound 125I-DT is plotted against the concentration of competitors, the recombinant mature Hu HB-EGF (◊, ⧫) or the recombinant mature Mk HB-EGF (□, ▪), in the absence (◊, □) or the presence (⧫, ▪) of heparin (10 U/ml). The average from duplicate wells was calculated and plotted. Results are representative of at least two separate experiments.