Binding of heparin to human microvascular endothelial cells and the effect on proliferation

We have studied the binding of 125I-heparin to human omental microvascular endothelial cells (HOME cells) and investigated its effect on cell proliferation. At 20 degrees C, the binding reached a steady state from 4 hours onwards. Saturation of 125I-heparin binding occurred at 200 nM. Scatchard analysis indicated one class of binding sites (KD = 0.023 microM, 2 X 10(-6) sites/cell). Using fractionated heparin and other sulfated polysaccharides it was demonstrated that the binding was dependent on the charge and the molecular weight of the compounds. The binding was followed by the partial internalization of the bound ligand (23.8%). Heparin and Stipocus Japonicus mucopolysaccharide (SJAMP) inhibited the proliferation of exponentially growing HOME cells and human umbilical vein endothelial cells (HUVE cells). However, serum-deprived HOME cells were not inhibited by heparin.