Gunnar Carlin

Effect of Dextran on Fibrinolysis Inhibition Activity in the Blood after Major Surgery

Patients undergoing total hip replacement surgery were given 500 ml of 6% dextran 70 or 5% albumin by intravenous infusion on the third postoperative day when the post‐traumatic fibrinolysis inhibition has reached its maximum. The large increase in the fibrinolysis inhibition activity measured by a clot‐lysis system was counteracted by the infusion of dextran, whereas the albumin infusion had no such effect. The plasma concentration of antiplasmin (chromogenic substrate assay) and the immunologically determined plasma levels of the primary fibrinolysis inhibitor (an‐antiplasmin), an‐macroglobulin, α2‐antitrypsin and plasminogen were not changed after the infusion of dextran. It is hypothesized that dextran exerts its effect partly by interfering with the interaction between the primary fibrinolysis inhibitor, fibrin and plasrnin(ogen) and by enhancing the activation rate of plasminogen. This observed effect of dextran may be of importance in the prevention of deep venous thrombosis and pulmonary embolic complications, as well as pulmonary microembolism.

On the interaction between dextran and the primary fibrinolysis inhibitor α2-antiplasmin

Abstract The mechanism underlying the effect of dextran on the lysis of plasma clots was studied. With the aid of 125 I-plasminogen, the formation of radiolabelled derivatives of urokinase-induced plasminogen activation was followed in clotted plasma. The activation was enhanced by the presence of dextran, but the rate of formation of the complex between plasmin and α 2 -antiplasmin was not. By measuring the amount of plasmin activity remaining after addition of plasmin and α 2 -antiplasmin to clots or fibrinogen solutions, it was found that in purified fibrin clots the α 2 -antiplasmin activity was impaired in the presence of dextran. In fibrinogen solutions dextran appeared to have no effect on the α 2 -antiplasmin activity. It is concluded that two different mechanisms are involved in the dextran-induced improvement of plasma clot lysis - an increased plasminogen activation rate and decreased α 2 -antiplasmin activity. The latter effect is apparently dependent on the morphologically different type of fibrin formed in the presence of dextran.

Effect of dextran on fibrinolysis inhibition activity in serum.

Abstract Clots derived from blood taken from rabbits infused with dextran were lysed much faster than normal clots. The fibrinolysis inhibition activity of serum was decreased and the clot lysis effect of dextran seemed to be due to a serum factor rather than to an altered fibrin network. The effect of dextran on the fibrinolytic activity of serum was present both after in vivo infusion to rabbits and after in vitro addition of dextran to human and rabbit sera.

Influences on the formation and structure of fibrin

Abstract Scanning electron micrographs of fibrin and clotting time measurements were used to investigate the effects of pH and ionic strength on fibrin formation. The influence of fibrinogen and various polymers were also studied. No general relationship was found between clotting time and fibrin structure, although in the presence of the uncharged polymers, the clotting time was decreased and the fibrin fibre diameter greater when compared to normal. Possible explanations for the effects of polymers on the structure of a fibrin clot were discussed.

Studies on α2-antiplasmin in the rat

Abstract Antibodies were raised against the plasmin-α2-antiplasmin complex in the rat and found monospecific against α2-antiplasmin after absorption. After gel filtration of normal rat serum the α2-antiplasmin peak (immunological assay) was observed at the same position as the antiplasmin activity (amidolytic assay), and their position in the chromatogram was similar to that of the human α2-antiplasmin. After in vitro activation of rat plasma and 125I-labelled rat plasminogen with urokinase, the plasmin-α2-antiplasmin complex was formed very rapidly after the start of the reaction. The plasmin-α2-macroglobulin complex also appeared almost immediately, but the formation rate was slow. Alpha2-antiplasmin-depleted rat plasma had no immediate inhibitory effect on plasmin, whereas normal rat plasma inhibited plasmin considerably. These results indicate that α2-antiplasmin is a primary plasmin inhibitor in the rat. The coefficient of var iation of α2-antiplasmin in normal rats was 8.2 7. It is concluded that the rat possesses a plasmin inhibitor with essentially the same properties as human α2-antiplasmin. The rat would therefore seem to be a suitable animal for studies of fibrinolysis inhibition.

Studies on biosynthesis of α2-antiplasmin in rat liver cells

Abstract Biosynthesis, intracellular processing and secretion of α2-antiplasmin (AP) were studied in primary cultures of rat hepatocytes by the pulse-chase technique. The experiments demonstrated that AP is present intracellularly as a 73 kD form and is secreted as a 79 kD form with affinity for human plasminogen kringles. Addition of human plasmin to the culture medium resulted in the formation of a 141 kD protein, probably a plasmin-AP complex, concomitantly with the disappearance of the 79 kD protein. The presence of tunicamycin, a blocker of N-linked glycosylation in the endoplasmic reticulum, during culture resulted in expression of a 63 kD form in medium and cell lysates. This latter form was unchanged after reduction and displayed affinity for human plasminogen kringles. The 79 kD form in the culture medium was resistant to treatment with endo-β-N-acetylglucosaminidase-H while the intracellular 73 kD form was degraded to 63 kD, indicating glycosylation in the Golgi complex. It is concluded that rat AP is synthesized in a 63 kD form which is glycosylated in the endoplasmic reticulum to a 73 kD form; and that this in turn is trimmed and glycosylated further in the Golgi complex to the 79 kD form, which is secreted. The glycosylation is apparently not necessary for the secretion or for the affinity for human plasminogen kringles.

Fibrinolysis Inhibition after a Major Standardized Trauma

The present investigation on 20 patients after total hip replacement surgery has confirmed that the posttraumatic increase of the fibrinolysis inhibition activity (FIA) in serum and plasminogen-depleted serum is due to the primary fibrinolysis inhibitor (PFI, alpha 2-antiplasmin). This protein exists in at least two forms and it was indicated that PFI alpha with affinity to immobilized plasminogen, is mainly responsible for the posttraumatic variations of the FIA in plasminogen-depleted serum. PFI beta, the major part of the PFI-related antigen, which has none or low such affinity, displayed weak FIA and relatively small increase after the surgical trauma. It was established that the posttraumatic increase of the FIA was not derived from the low molecular weight fraction in serum of those patients.

Inhibition of Heme-promoted Enzymatic Lipid Peroxidation by Desferrioxamine and EDTA

Oxyhemoglobin, methemoglobin and hematin were found to catalyze xanthine-oxidase-induced peroxidation of phospholipid liposomes, while oxy- and metmyoglobin were inactive in this respect. The peroxidation was inhibited by desferrioxamine and by EDTA. Peroxidation catalyzed by 0.4 microM oxyhemoglobin was decreased by 50% by approximately 2 microM desferrioxamine or 20 microM EDTA and completely inhibited by 10 microM desferrioxamine or 100 microM EDTA. Inhibition of hemoglobin-catalyzed peroxidation was not accompanied by any changes in the absorbance spectra of hemoglobin, indicating that the heme iron was not withdrawn by the inhibitor. Inhibition of hematin-catalyzed peroxidation by desferrioxamine may have been due to iron chelation and removal, as judged from changes in absorbance spectra. The peroxidation was apparently not dependent on hydrogen peroxide since catalase did not inhibit peroxidation but on the contrary promoted it in some cases.

Two Forms of α2-antiplasmin: Post-traumatic Changes in the Rat

The plasminogen-binding (PB-AP) and non-plasminogen-binding (NPB-AP) forms of alpha 2-antiplasmin (AP), were assayed in rat plasma by a modified rocket immunoelectrophoretic technique before and up to 48 h after turpentine-induced trauma, using an intermediary gel containing kringles 1-3 from plasminogen. The concentration of PB-AP was significantly elevated by 22% 24 h post-traumatically, while NPB-AP was decreased at that point in time, leaving the total AP level unchanged. Total AP increased by 57% during the period 24-48 h after trauma, mainly on account of increases in the NPB-AP form. It is concluded that the plasma level of AP can remain unchanged in spite of increased fibrinolysis inhibition, owing to a relative increase in the functionally more active PB-AP.

Urokinase-induced Fibrin Clot Lysis and its Inhibition by Plasma

The kinetics of the urokinase-induced plasmin digestion of fibrin clots has been studied. Some theoretical aspects on the kinetics of the underlying enzyme reactions are presented. It is shown that the clot-lysis time may be used to measure the relative amounts of fibrinolysis inhibitors in plasma.