Fibrinolytic and plasmin inhibitor activities in patients with acute myocardial infarction

Fibrinolytic activity and plasmin inhibitor activity were determined by Blue Dextran-fibrin method in patients with acute myocardial infarction. The normal values of fibrinolytic activity and plasmin inhibitor activity were 3.34 +/- 0.74 units and 10.10 +/- 2.39 units (mean +/- SD), respectively. The fibrinolytic activity in normal women (3.63 +/- 0.99 units) was slightly higher than that in normal men (3.17 +/- 0.79 units), but the plasmin inhibitor was not significantly different in the two sexes statistically. Neither activity varied significantly with age. The blood fibrinolytic activity was depressed in the first week after acute myocardial infarction, the decrease being maximal 3 to 4 days after the event (1.73 +/- 0.31 units). The mean plasmin inhibitor activity remained normal after acute myocardial infarction, but it was increased in 3, and decreased in 4 of 7 patients in whom it was measured 3 to 4 days after the event.

Alpha2-plasmin inhibitor and alpha2-macroglobulin-plasmin complexes in plasma. Quantitation by an enzyme-linked differential antibody immunosorbent assay

An enzyme-linked differential antibody immunosorbent assay has been developed for the quantification of alpha2-plasmin inhibitor-plasmin and alpha2-macroglobulin-plasmin complexes. In this method the inhibitor-plasmin complex is bound to a surface by an inhibitor-specific antibody, and the plasmin bound to the inhibitor is quantified by a second antibody, rabbit antiplasminogen F(ab')2, labeled with alkaline phosphatase. The hydrolysis of p-nitrophenyl phosphate by the alkaline phosphatase is expressed in femtomoles of plasminogen per milliliter, by reference to a standard plasminogen curve. Inhibitor-enzyme complexes were generated in plasma by the addition of plasmin or of urokinase. The concentration of plasmin added was well below the plasma concentration of alpha2-plasmin inhibitor (1 microM) or of alpha2-macroglobulin (3.5 microM), so that neither inhibitor would be fully saturated with enzyme. Under these conditions increasing amounts of plasmin generated an increase in both alpha2-plasmin inhibitor-plasmin and alpha2-macroglobulin-plasmin complexes. Varying amounts of plasmin were incubated with each of the purified inhibitors in the concentration found in plasma, and the complexes. Varying amounts of plasmin were incubated with each of the purified inhibitors in the concentration found in plasma, and the complexes that formed were quantified by immunoassay. These studies made it possible to quantify the distribution of plasmin between the two inhibitors in plasmin or urokinase-treated plasma. In plasmin-treated plasma, 10% or less of the plasmin bound to both inhibitors was in complex with alpha2-macroglobulin. In contrast, between 19 and 51% of the plasmin generated in urokinase-activated plasma was bound to alpha2-macroglobulin. Thus, major changes in the distribution of plasma were observed, according to whether plasmin was added to plasma or whether plasminogen was activated endogenously. The pattern of inhibitor plasmin complexes generated in vivo by the therapeutic infusion of urokinase was similar to that found for urokinase-activated plasma. 23 normal individuals had low levels of alpha2-plasmin inhibitor-plasmin complexes, whereas six patients with laboratory evidence for disseminated intravascular coagulation demonstrated a 16- to 35-fold increase in he concentration of these complexes. These data indicated that a useful new probe for the study of the fibrinolytic enzyme system had been developed.

Inactivation of trypsin-like proteases by depsipeptides of p-guanidinobenzoic acid

A number of esters of p-guanidinobenzoic acid have been synthesized which contain a glycolyl peptide as the departing group. In the case of several enzymes such as trypsin and plasma kallikrein, depsipeptides were obtained which were considerably more reactive than the ethyl ester in inactivation of the protease by acyl-enzyme formation; the depsipeptide processing -CH2CO-Phe-NH2 as a leaving group displayed the highest reactivity. They were less effective in the case of urokinase, plasmin, and urinary kallikrein. Boar acrosin was very susceptible to inactivation by both ethyl and peptidyl esters. Depsipeptides possessing a longer peptide chain and a secondary carbon as a leaving group showed lower activities. The results demonstrate the productive use of the departing group region of protease active centers to obtain selectivity.

Fibrinolysis-inhibitory activity of cultured human cancer cell lines

Fibrinolysis-inhibitory activity was estimated in the lysates of 21 lines of cultured human cancer cells, from which plasminogen activator activity had veen effectively eliminated by affinity chromatography. Inhibitory activity against urokinase varied from one line to another. Three lines of lung cancer and 1 line of urinary bladder cancer showed high inhibitory activity against urokinase. Two lines of lung cancer, 3 lines of gastric cancer, 1 line of renal cancer and 1 line of renal pelvic cancer showed moderate inhibitory activity. Since inhibitory activity against plasmin was not apparent in all the cell lines tested, this activity seemed to be directed selectively towards urokinase. No inhibitory activity against urokinase was detected in 4 lines of lung cancer, 5 lines of gastric cancer and 1 line of renal cancer. There was no specific correlation between the degree of inhibitory activity against urokinase and the histological cell types of the original tumors of the cultured cell lines.

The effect of the anabolic steroid stanozolol on tissue plasminogen activator activity and plasmin inhibition in the rat

The anabolic steroid stanozolol administered orally in male Sprague-Dawley rats induced a dose- and time-dependent increase in tissue plasminogen activator activity. The increase was highest in lung, lowest in heart, and intermediate in aorta and kidney. A slight increase in plasmin inhibition was noted only in the heart.

Activation of factor XII in plasma from rats pretreated with tranexamic acid. Inhibition of a plasmin-induced loss of the functional activity of high molecular weight kininogen

Incubation of plasma from rats pretreated with tranexamic acid (40 mg/100 g) with acetone (23% V/V) yielded enzyme preparations in which all the plasminogen present was recovered as plasmin and a plasmin-like substance without affinity for lysine-Sepharose. This substance, designated "plasmin", was separated from plasmin and kallikrein in a three-step procedure using columns of lysine-Sepharose, DEAE-Sephadex A-50, and arginine-Sepharose. The ratios of fibrinolytic, caseinolytic, LEe esterase, BAEe esterase and kininogenase activities of "plasmin" corresponded well with those of rat plasmin and human plasmin. Both rat plasmin and "plasmin" destroyed the capacity of high molecular weight kininogen (HMWK) to function as a cofactor in the activation of factor XII in rat plasma, without causing a corresponding release of the kinin part of the molecule. Rat plasma kallikrein induced full release of kinin from HMWK, but the functional capacity was retained. It is suggested that the reduced extent of activation of factor XII observed in plasma from rats injected intravenously with dextran, or rat plasma that has been passed through a column with lysine-Sepharose, is due to the loss of functional HMWK caused by plasmin activated in vivo or on the column.