Plasma Fibrinolytic Activity in the Immature Animal

Abstract

FOLLOWING the demonstration that hyaline membrane formation in adults¹ is related to upset of fibrinolysis and that pulmonary hyaline in new-born infants consists predominantly of fibrin², some of the recent work in this field has been directed to the investigation of possible abnormalities of fibrinolytic mechanisms in the lungs of these children. Lieberman³, for example, has shown that extracts of lung contain a specific inhibitor of plasminogen activator in many of the children who have died from this condition and presents evidence that the placenta may release such inhibitors when undergoing degenerative changes. Briefly, the mechanism in the normal individual is that plasminogen activator, a tissue enzyme, converts plasminogen to plasmin, the active fibrinolytic enzyme of the body. An alternative hypothesis is that hyaline membrane fibrin has its origin in plasma fibrinogen which, because of circulatory disturbances, enters the alveoli as a transudate⁴.