Cell surface fibronectin of mouse peritoneal macrophages

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Abstract
Fibronectin (FN) was detected on thioglycollate‐induced mouse peritoneal macrophages by binding the 125I‐labeled F(ab′)2 fragment of rabbit anti‐human plasma fibronectin. The cell surface fibronectin (sFN) was removed from the surface of the macrophage monolayer by limited trypsinization. After trypsinization, binding of 125I‐labeled plasma fibronectin (125I‐pFN) to the macrophage monolayer was increased, suggesting that the FN receptor covered with sFN was exposed by trypsinization without destroying the receptor activity. The amounts of saturation binding of 125I‐pFN to the macrophage monolayers before and after trypsinization were about 2.4 and 6.3 μg per 106 cells, respectively, indicating that the macrophage monolayer has the capacity of binding 6.3 μg FN per 106 cells, and the FN receptor equivalent to about 4 μg pFN per 106 cells is covered with sFN.