Leukocyte elastase in plasma and serum was measured by an enzyme-linked immunosorbent assay (ELISA) and the amidolysis using a synthetic substrate for leukocyte elastase, Suc-Ala-Tyr-Leu-Val-pNA. Leukocyte elastase (ELP) values in plasma and serum from healthy donors were 125±35 and 341±57ng/ml (ELISA) and 139±55 and 222±69ng/ml (amidolysis), respectively. But ELP values in serum separated by a blood collecting tube, AUTO-SEP, increased to 545±219ng/ml (ELISA) and 277±95ng/ml (amidolysis). Correlation coefficients between ELP in plasma and serum from patients were 0.36 (ELISA) and 0.86 (amidolysis). Furthermore, the variations of ELP values were approximately parallel when ELP in plasma and serum continuously obtained from some patients was measured by the amidolysis. Excepting leukocytes number, fibrinogen level was closely connected with the elevation of serum ELP level. The increase of fibrinogen in blood from patients was accompanied by the elevation of ELP and FDP without the decrease of plasminogen and antithrombin III. The increase of fibrinogen in inflammation may possibly cause fibrinogenolysis by ELP.
