Fibronectin--a plasmin-sensitive glycoprotein of the transit zone: protection by aprotinin.

Intravascular and extravascular fibronectin represents an essential "early information-transmitting" molecule of the transit zone. It appears to play a part especially in the flow of information provoked by sympathetic reactions (every form of stress), which is associated with a rise in plasmin levels. The rapid proteolytic cleavage of fibronectin by plasmin alters the composition of the ground substance, hence its informational contents. This is transmitted to the glycocalyx of affected cells, provoking a reaction typical of those particular cells. When a stress goes beyond the physiological margin of tolerance, an excessive break-down of fibronectin quickly ensues so that the transit zone will transmit faulty information. It has been demonstrated on human and animal tissue that initial use of the potent plasmin inhibitor aprotinin (Trasylol) can provide a selective protection of fibronectin and, consequently, of the transit zone. Clinical results obtained in patients with multiple injuries corroborate this observation.