The binding of high molecular weight kininogen to cultured human endothelial cells.
Binding of 125I-labeled high molecular weight kininogen (high Mr kininogen) to cultured human endothelial cells derived from the umbilical cord was demonstrated. The binding was time-dependent, specific, and saturable and required the presence of zinc ions. Maximal binding of 125I-labeled high Mr kininogen was observed at 50 microM Zn2+. Calcium ions inhibited the Zn2+-dependent binding of 125I-labeled high Mr kininogen to endothelial cells. In the presence of 3 mM CaCl2 the total binding of 125I-labeled high Mr kininogen was significantly decreased, and a concentration of 100 microM Zn2+ was then required for the binding of 125I-labeled high Mr kininogen to the cells. Higher calcium concentrations did not further decrease the binding of 125I-labeled high Mr kininogen. Analysis of the binding data by the LIGAND computer program indicated 3.2 X 10(6) binding sites per cell for high Mr kininogen with an apparent Kd of 35 nM at 50 microM ZnCl2 and 1 mM CaCl2. Binding of high Mr kininogen also occurred at physiological plasma Zn2+ concentrations. Saturation of the high Mr kininogen binding sites at 25 microM ZnCl2 occurred at 80 nM of high Mr kininogen with 2.8 X 10(6) molecules of high Mr kininogen bound per cell. At 10 microM ZnCl2, the high Mr kininogen binding sites appeared to be saturated at 130 nM with 1.6 X 10(6) molecules bound per cell. In addition it was demonstrated that endothelial cells internalize 125I-labeled high Mr kininogen, since 125I-labeled high Mr kininogen was detected in solubilized endothelial cells after the cell-bound 125I-labeled high Mr kininogen had been removed with dextran sulfate.
van Iwaarden
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F
Department of Haematology, University Hospital Utrecht, The Netherlands.
de Groot
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PG
Bouma
B N
BN
D002122:Calcium Chloride / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D007704:Kininogens / Q000378:metabolism*; D008970:Molecular Weight; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D018000:Receptors, Peptide; D014471:Umbilical Veins / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology; D017967:Zinc Compounds
D002712:Chlorides; D007457:Iodine Radioisotopes; D007704:Kininogens; D017981:Receptors, Neurotransmitter; D018000:Receptors, Peptide; D017967:Zinc Compounds; C044865:kininogen receptor; C016837:zinc chloride; D015032:Zinc; D002122:Calcium Chloride