Plasminogen activator inhibitor activity in bacterial infection.

It has been experimentally shown that endotoxin induces a marked increase in the levels of a fast-acting inhibitor of plasminogen activator (PAI). The plasma PAI activity and tissue-type plasminogen activator (t-PA) concentrations were measured in 61 patients with human septicaemia and results were compared with those observed in healthy controls. There was a markedly significant increase of PAI in plasma and platelet extracts of patients with septicaemia as compared to controls (p less than 0.0001). No correlation between PAI and endotoxin concentration was observed. Fibrin autography of plasma samples confirmed that activator inhibition was associated with the formation of an enzyme-inhibitor complex. t-PA activity was similar in patients and controls, whereas t-PA Ag showed a significant increase in patients (p less than 0.0001). A significant inverse correlation between t-PA activity and PAI was observed (p less than 0.05). PAI activity was higher in patients with positive blood cultures (p less than 0.0001) and gram-negative septicaemia (p less than 0.0001). There was also a significant increase of PAI levels in patients with disseminated intravascular coagulation (DIC) as compared with patients without DIC (p less than 0.001). We conclude that there is a marked increase of PAI in patients with sepsis. Increased PAI activity may contribute to the pathogenesis of DIC associated with septicaemia.