Synthesis of fibronectin, laminin, and several collagens by a liver-derived epithelial line

We have investigated the ability of ARL-6 cells, a cell line derived from rat liver, to synthesize various collagens and two glycoproteins of the extracellular matrix, fibronectin, and laminin. Using immunofluorescence, we detected types I, II, and IV collagen plus laminin and fibronectin. Antibodies to types I and III collagen and to fibronectin were associated with most cells and showed a similar distribution. Type IV collagen and laminin were found in thin filaments associated with a small proportion of the cells. Chemical studies showed that ARL-6 cells synthesize predominantly types I and III collagens. The level of collagen synthesis was greatly affected by the presence of exogenous fibronectin added to the cells in the media. Cells maintained in fibronectin-free serum synthesized much less collagen. These studies indicate that liver-derived cells can synthesize a variety of connective tissue proteins and that collagen synthesis by these cells is enhanced by the presence of fibronectin.