[Valve of a freeze-dried gelatin-agarose combination in selective extraction of fibronectin from human plasma].

We report here a simple procedure for the isolation of human plasma fibronectin by affinity adsorption on a new lyophilized adsorbent which is obtained by mixing and polymerizing agarose with gelatin. This method permits to obtain fibronectin and a fibronectin-depleted plasma without dilution. The yield of fibronectin is about 20 to 25 per cent. Fibronectin was identified by cross-reactions against specific antibodies. Its purity (greater than or equal to 99 per cent) was controlled by immunoelectrophoresis and SDS-PAGE. Furthermore, its biological activity was demonstrated by a spreading test performed on BHK cells. Such a test can be used to determine the specific activity of extracted fibronectin considering that the number of spread cells placed in presence of exogenous fibronectin (5 microgram/ml of culture medium) was 4.5 to 5 fold-superior to the control, after 30 minutes of incubation at 37 degrees C.