The Effect of Pentosan Polysulphate (SP54) on the Fibrinolytic Enzyme System - A Human Volunteer and Experimental Animal Study

Pentosan polysulphate causes an increase in plasminogen activator activity in plasma both after oral ingestion and after subcutaneous injection. The effect is greatest after 3 h and has disappeared by 6 h. Repeat doses by mouth over 5 days elicit a similar response. The recorded increase in activity is due largely to the release of tissue-type plasminogen activator (tPA) from the endothelium according to the antigen assay although there could be a small contribution from Factor XH-related “intrinsic” fibrinolysis induced in vitro. SP54 enhances activity ex vivo by a non-specific surface effect, and this phenomenon may contribute the increased levels of activity seen in vitro. Administration of SP54 to animals elicits a similar increase in activator activity, the intramuscular route being slightly more effective. Results with an inferior vena cava thrombosis model in the rat suggest that pentosan polysulphate may induce a thrombolytic effect.

Bioavailability in Rats of Human Recombinant Tissue Plasminogen Activator After Subcutaneous and Intramuscular Injection

The bioavailability of human recombinant tissue plasminogen activator (rt-PA) in rats was measured after subcutaneous (s.c.) and intramuscular (i.m.) injection. Rt-PA was absorbed after both i.m. and s.c. injection, giving peak plasma concentrations within 30 min and 1 h, respectively, with detectable concentrations up to 6 h. These peak values of bioavailable t-PA were obtained in a functional fibrin plate assay of euglobulin precipitates and expressed as +88% and +243% (for s.c. and i.m. routes respectively) above basal rat fibrinolytic activity. Prior injection of rt-PA, s.c. or i.m., significantly reduced the weights of thrombi induced in the inferior vena cava after injection.

Imaging of human thrombi in the rabbit jugular vein: I: Comparison of two fibrin-specific monoclonal antibodies

The development of monoclonal antibodies with a specificity for cross-linked fibrin may have a potential role in the detection and of thrombi and thrombolytic therapy. In this study, two monoclonal antibodies with a specificity for fibrin have been examined. In vitro studies have shown NIBn 123 (which has a high affinity for X-oligomer) and DD-3B6 to bind to immobilised fibrin on PVC plates as well as plasma clots which were incubated in the presence of plasma. The Km values for NIBn 123 and DD-3B6 wre 1.0 x 10(10)/7.7 x 10(8) M and 2.6 x 10(8) M respectively. No significant binding to fibrinogen either immobilised or in solution was found. The binding of these antibodies to a human thrombus in the jugular vein of the rabbit was monitored over a 24 hour period. Preferential binding of each antibody reached a ratio of approximately 1.0 (jugular/heart) at 24 hours and an image was detected.

Investigation by HPLC of the catabolism of recombinant tissue plasminogen activator in the rat

The catabolism of recombinant tissue plasminogen activator (rt-PA) was investigated after injection of radiolabelled material into rats. Both Iodogen and Chloramine T iodination procedures yielded similar biological activity loss in the resultant labelled rt-PA and had half lives in the rat circulation of 1 and 3 min respectively. Complex formation of rt-PA was investigated by HPLC gel exclusion (TSK G3000 SW) fractionation of rat plasma samples taken 1-2 min after 125I-rt-PA injection. A series of radiolabelled complexes of varying molecular weights were found. However, 60% of the counts were associated with a single large molecular weight complex (350-500 kDa) which was undetectable by immunologically based assays (ELISA and BIA) and showed only low activity with a functional promoter-type t-PA assay. Two major activity peaks in the HPLC fractions were associated with free t-PA and a complex having a molecular weight of approximately 180 kDa. HPLC fractionation to produce these three peaks at various timed intervals after injection of 125I-rt-PA showed each to have a similar initial rate half life in the rat circulation of 4-5 min. The function of these complexes as yet is unclear but since a high proportion of rt-PA is associated with a high molecular weight complex with a short half life in the rat, we suggest that the formation of this complex may be a mechanism by which t-PA activity is initially regulated and finally cleared from the rat circulation.

Monoclonal antibodies to crosslinked fibrin degradation products (XL-FDP). I. Characterization and preliminary evaluation in plasma

Monoclonal antibodies (mabs) were raised against X-oligomers, the earliest soluble fragments released from crosslinked fibrin (XL-FN), by the action of plasmin. Two of the mabs (NIBn 52 and NIBn 123) were monospecific for X-oligomers in that they showed no binding to fibrinogen, the plasmic fragments of fibrinogen (D and E) and non-crosslinked fibrin (X, Y, D and E), or the terminal digestion product of XL-FN, fragment DD-E. One other mab (NIBn 178) was panspecific for X-oligomers in that it exhibited a weak affinity for fibrinogen. The mabs were used to develop a two-site immunoradiometric assay (IRMA) and an enzyme-linked immunospecific assay (ELISA) which permitted the specific measurement of X-oligomers directly in plasma, rather than in serum. This immunoassay is a true assay of fibrinolysis as distinct from fibrinogenolysis and may be a potential aid in the diagnosis and evaluation of thrombosis. In preliminary studies, the assay detected low levels of X-oligomers in normal plasma and elevated levels in patients with disseminated intravascular coagulation.

Monoclonal antibodies to crosslinked fibrin degradation products (XL-FDP). II. Evaluation in a variety of clinical conditions

Plasmas from patients with a wide variety of thrombotic and presumed prethrombotic conditions were examined for high molecular weight crosslinked fibrin degradation products (known as X-oligomers) using a two-site enzyme-linked immunospecific assay (ELISA). This assay employed a catcher-tag principle using two monoclonal antibodies (mabs) directed towards different epitopes on the complex X-oligomer fraction. In general, thrombotic events (pulmonary embolism, PE, myocardial infarction, MI, peripheral vascular disease, PVD, and disseminated intravascular coagulation, DIC) were accompanied by elevated levels of X-oligomers in the plasma. During pregnancy the value of X-oligomer assays was demonstrated to be a clear-cut marker for pre-eclampsia. Patients following a variety of forms of surgery present with heterogeneous plasma levels of X-oligomers and this may merely reflect the formation and lysis of the fibrin formed during and after surgery. The possible value of this ELISA procedure in monitoring thrombolytic therapy is discussed with a critical analysis of the data presented herein. While the assay of X-oligomer was demonstrated to be a valuable marker of fibrinolysis in plasma, more extensive data are required in order to assess whether such an assay is of diagnostic value in thrombosis-related conditions.

Diabetes mellitus as a hypercoagulable state: its relationship with fibrin fragments and vascular damage

Haemostatic variables were assessed in 43 patients, 28 insulin-dependent and 15 non insulin-dependent. Maximum aggregation by low concentrations of adenosine diphosphate (ADP) or arachidonic acid and elevated plasma concentrations of TxB2, Factor VIII, vWF:Ag, RCoF and fibronectin (Fnct) indicated a hypercoagulable state. The manifestation of vasculopathy was associated with elevated concentrations of RCoF, Fnct, Hbalc, cholesterol and triglycerides, while impaired fibrinolysis was demonstrated by decreased t-PA levels and the absence of crosslinked fibrin degradation products (XL-FDP).

Changes in fibrinolysis in the intensive care patient

Critically ill patients have been described as having blood coagulation abnormalities that predispose to bleeding and thrombosis. We have studied plasminogen activators, alpha 2-antiplasmin, X-oligomers fibrin fragments, fibronectin, antithrombin III, fibrinogen, platelets, kaolin-cephalin clotting time and prothrombin time on admission to the intensive care unit and sequentially after 24 and 48 hours in 39 adult patients: ARDS (n = 6), trauma (n = 12), sepsis (n = 8) and a miscellanea (n = 13). A decrease in plasminogen activators associated with an increase in X-oligomers, the earliest form of cross linked fibrin degradation products, indicate that fibrin deposition and the consumption of components of fibrinolysis is a widespread condition in the ICU patients. Low fibronectin levels were related to prognosis. These findings suggest that critically ill patients must be evaluated in respect to fibrinolysis and supported when necessary with prophylactic treatment.

Bioavailability in rats of human recombinant tissue plasminogen activator after subcutaneous and intramuscular injection

The bioavailability of human recombinant tissue plasminogen activator (rt-PA) in rats was measured after subcutaneous (s.c.) and intramuscular (i.m.) injection. Rt-PA was absorbed after both i.m. and s.c. injection, giving peak plasma concentrations within 30 min and 1 h, respectively, with detectable concentrations up to 6 h. These peak values of bioavailable t-PA were obtained in a functional fibrin plate assay of euglobulin precipitates and expressed as +88% and +243% (for s.c. and i.m. routes respectively) above basal rat fibrinolytic activity. Prior injection of rt-PA, s.c. or i.m., significantly reduced the weights of thrombi induced in the inferior vena cava after injection.

The effect of pentosan polysulphate (SP54) on the fibrinolytic enzyme system--a human volunteer and experimental animal study

Pentosan polysulphate causes an increase in plasminogen activator activity in plasma both after oral ingestion and after subcutaneous injection. The effect is greatest after 3 h and has disappeared by 6 h. Repeat doses by mouth over 5 days elicit a similar response. The recorded increase in activity is due largely to the release of tissue-type plasminogen activator (tPA) from the endothelium according to the antigen assay although there could be a small contribution from Factor XII-related "intrinsic" fibrinolysis induced in vitro. SP54 enhances activity ex vivo by a non-specific surface effect, and this phenomenon may contribute the increased levels of activity seen in vitro. Administration of SP54 to animals elicits a similar increase in activator activity, the intramuscular route being slightly more effective. Results with an inferior vena cava thrombosis model in the rat suggest that pentosan polysulphate may induce a thrombolytic effect.