FIBRINOLYSIS IN NORMAL PLASMA AND BLOOD - EVIDENCE FOR SIGNIFICANT MECHANISMS INDEPENDENT OF PLASMINOGEN-PLASMIN SYSTEM

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  • 1 January 1976
    • journal article
    • research article
    • Vol. 48  (4) , 531-545
Abstract
Fibrinolytic activity of normal plasma [human] and blood was measured by 125I-fibrin solid phase assay. Activity of plasma was not affected by removal of plasminogen-plasmin by affinity chromatography. Activities of euglobulin and pseudoglobulin fractions were approximately equal. .epsilon.-Aminocaproic acid (EACA) (10 mM), tranexamic acid (10 mM), diisopropylfluorophosphate (DFP, 50 mM), and soybean and lima bean trypsin inhibitors (100 .mu.g/ml) did not inhibit plasma activity at concentrations that inhibited pure plasmin and urokinase-activated plasma. Activity was not affected by glass contact and was not inhibited by inhibitors of contact or enzymatic activation of Hageman factor (hexadimethrine bromide, 100 .mu.g/ml; cytochrome c, 250 .mu.g/ml; spermidine, 2 mM phenylmethylsulfonylfluoride, 1 mM). It was inhibited partially (30-40%) by heating (56.degree. C, 30 min) and by zymosan (2.5 mg/ml; 40-90% inhibition), and was increased by hydrazine (20 mM), salicylaldoxime (20 mM), DFP (50 mM), and tosyl-L-arginine methyl ester (TAMe, 10 mM).sbd.the latter 2 at concentrations known to inhibit C.hivin.ls [activated S fragment of 1st complement component] of the classic, and factor .hivin.D of the alternate complement pathways. Increased fibrinolytic activity with TAMe was associated with reciprocal decrease in classic and alternate complement pathway activity. Normal plasma fibrinolytic activity was apparently relatively independent of plasmin as the ultimate fibrinolytic enzyme; Hageman factor-dependent pathways were probably of minor importance and significant heat-stable and heat-labile nonplasmin fibrinolytic activities were operative. These may include proteinases involved in complement activation, and in common control of classic and alternate complement pathways, as well as other nonplasmin proteinases.

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