Glycoprotein and fibronectin metabolism in cutaneous fibroblasts of patients with rheumatoid arthritis

The fibronectins are high-molecular-weight glycopr0teins found in blood plasma and the extracellular matrix and basal and cytoplasmic membranes of various types of cells [Ii]. Fibronectin plays an active role in the regulation of various processes during the formation of connective tissue [8, 13], it is a protein secreted by the cells of this tissue, and is capable of interacting with several of its components (fibrin, collagen, glycosaminoglycans), connected with the organization and repair of injured or inflamed tissue [9, ii]. In rheumatoid arthritis (RA) the fibronectin concentration in a cell monolayer of cutaneous fibroblasts from patients in culture is higher than normal [2]. Fibronectin is more sensitive to the action of various proteinases than basement membrane proteins of cells such as laminin and type IV collagen [4]; removal of fibronectin from the surface of cells by means of proteinases, moreover, leads to stimulation of their proliferation [2, 5].