Figure 2.

Quantitation of fibronectin matrix turnover. Fibronectin-null cells were incubated overnight with ¹²⁵I-fibronectin. Cells were then either processed to determine the amount of matrix-associated fibronectin or were washed and then incubated with culture medium lacking or containing 10 or 20 nM unlabeled fibronectin for 12 or 23 h. Cells were then processed to determine the amount of matrix-associated fibronectin by extracting the cells in 1% DOC as described (Sottile and Wiley, 1994). The cell extract was centrifuged at 4°C at 18,000 × g for 30 min to separate DOC-insoluble (matrix-associated) from DOC-soluble (cell-associated) counts. The amount of matrix-associated counts before the chase was set equal to 100%. The data is presented as % loss of matrix-associated counts. Error bars represent the range of duplicate determinations.