Binding of fibrinogen to cultured bovine endothelial cells

The binding properties of purified bovine fibrinogen to bovine aortic endothelial cells have been examined in a tissue culture system. Endothelial cells bound 125I-fibrinogen in a calcium dependent fashion. Removal of calcium by EDTA instantaneously detached most of the cell-associated fibrinogen. Binding of fibrinogen to the endothelial cells was not saturable with time and dosage. Competition studies and displacement experiments did not indicate the involvement of a specific receptor site for the fibrinogen-endothelial cell-interaction. Bovine serum albumin provided in the physiological ratio of 20:1 to fibrinogen competed as effectively as unlabelled fibrinogen for 125I-fibrinogen binding to the endothelial cells. And furthermore, internalization of cell-associated tracer into the endothelial cells that could be demonstrated in the presence of serum free medium did not occur in the presence of albumin. These data suggest that fibrinogen binding to intact bovine endothelial cells is unspecific and presumably negligible in the presence of physiological albumin concentrations.