FIBRONECTIN EXPOSES DIFFERENT DOMAINS AFTER ADSORPTION TO A HEPARINIZED AND AN UNHEPARINIZED POLY(VINYL CHLORIDE) SURFACE

The adsorption of fibronectin to poly(vinyl chloride) catheters with e nd-point attached (EPA) heparin and tridodecylmethylammonium chloride- heparinized poly(vinyl chloride) was compared to that of unheparinized poly(vinyl chloride) using antibodies directed against four different domains of the protein. After perfusion of human plasma on the EPA-he parinized surface, the exposure of the N-terminal 29-kD fragment incre ased during the first 5h of perfusion. Also, the exposure of the 30-kD gelatin-binding and 65-kD cell-binding fragments increased with time, but at a lower level. On the unheparinized catheter, low levels of an tibodies bound to the different domains, and the binding showed little variation during the 5 h of plasma perfusion, indicating that the fib ronectin molecule does not change configuration to a significant exten t on this surface after the initial adsorption. When the EPA-hepariniz ed surface was preadsorbed with human fibrinogen before incubation wit h fibronectin, significantly less of the 29-kD (fibrin-binding) domain was exposed, and the 30-kD domain was not exposed. Exposure of the 31 - and 65-kD domains increased after preadsorption of fibrinogen to the surface. Since fibronectin has heparin-binding domains, it adsorbs di fferently to a heparinized versus an unheparinized surface. This will influence subsequent binding of other proteins to the surface, as well as potential binding of microbes. The use of antibodies to defined do mains of the fibronectin molecule provides a powerful tool in studies of configurational changes of fibronectin after adsorption to differen t surfaces. (C) 1997 Elsevier Science Limited. All rights reserved.