Functional Kallikrein Inhibition Research Articles

Plasma proteolytic activity in liver transplant rejection.

In this study, we evaluated the role of proteolytic enzymes belonging to the coagulation, fibrinolytic, and plasma contact systems in the early postoperative phase after orthotopic liver transplantation (OLT). Twenty-nine patients were studied at the time of OLT and during the first 2 postoperative weeks. Blood samples were collected daily after OLT and analyzed for kallikrein-like activity (KK), functional kallikrein inhibition (KKI), plasmin-like activity (PL), and alpha2-antiplasmin (AP). In addition, prekallikrein (PKK), prothrombin (PTH), antithrombin III (AT III), plasminogen (PLG), prothrombin/antithrombin III complexes (TAT), prothrombin fragment 1 + 2 (F1 + 2), and plasmin/alpha2-antiplasmin complexes (PAP) were measured. Nineteen patients experienced biopsy-verified acute rejections (AR) and ten patients had uneventful courses and served as controls. Plasma analyses showed that the contact, coagulation, and fibrinolytic systems were activated during OLT. Following OLT, continuous thrombin and plasmin generation was observed, and these effects were more pronounced in the group having an uneventful course than in patients with AR. Factors that could possibly affect plasma proteolytic activity, such as blood product usage during and after OLT and cold ischemia time of the liver graft, did not differ between the groups, nor did the routine liver function tests, alanine aminotransferase (ALT) and aspartate aminotransferase (AST).

Effects of heparin on proteolytic activities in human plasma.

The influence of unfractionated heparin [average molecular weight (MW) 10,000-15,000 kD] and low-molecular-weight heparin (average MW 400-600 kD) on the plasma kallikrein-kinin and the fibrinolytic system was studied in vitro. Unfractionated heparin added to plasma gave an increase in kallikrein-like activity with a corresponding decrease of prekallikrein and functional kallikrein inhibition values. Plasmin-like activity was also increased, but minor changes in plasminogen and no change in antiplasmin values occurred. The changes were less pronounced with low molecular heparin compared with unfractionated heparin. The proteolytic changes were reversed by protamine sulfate but not influenced by the protease inhibitor aprotinin. Gel filtration yielded proteolytic activities able to split the plasma kallikrein substrate S-2305 and, to a minor degree, the plasmin substrate S-2251. The proteolytic activities were not due to complex formation with alpha 2-macroglobulin. We speculate that heparin binds to prekallikrein to form a heparin-prekallikrein complex which undergoes conformational changes and displays a kallikrein-like activity with the ability to split small synthetic substrates. Whether it is capable to split natural substrates remains unresolved.

Different activation patterns in the plasma kallikrein-kinin and complement systems during coronary bypass surgery.

Components of the plasma kallikrein-kinin and complement systems were determined in patients undergoing open heart surgery with cardiopulmonary bypass. Spontaneous kallikrein activity (KK), plasma prekallikrein (PKK), functional kallikrein inhibition capacity (KKI), C3 activation products (C3-act), and the terminal complement complex (TCC) were measured. A marked, transitory increase in KK and a decrease in PKK were found prior to cardiopulmonary bypass just after heparin injection. An additional decline in PKK and KKI during bypass with a return to near control levels in the postoperative period was observed. C3-act increased in all patients during bypass, reaching a peak value at wound closure. The TCC concentration also increased significantly during cardiopulmonary bypass, returned to control levels in the early postoperative period, and then increased again in the late postoperative period. It is concluded that activation of the kallikrein-kinin system started after injection of heparin, prior to cardiopulmonary bypass. Activation of both the initial and the terminal complement cascade, however, started only after onset of cardiopulmonary bypass.

Changes in the Plasma Protease Systems During Open-Heart Surgery with Dextran vs. Ringer Acetate as Priming Solution

Two different priming solutions for cardiopulmonary bypass (CPB) were studied in regard to possible influence on the plasma protease systems. The study was performed on 20 patients undergoing elective coronary artery bypass grafting. In ten cases the priming solution contained 1,000 ml dextran (MW 70,000) and in ten it consisted only of Ringer's acetate solution. The same level of haemodilution was established during CPB in the two groups. Clinical variables and laboratory data were monitored. Spontaneous kallikrein activity, plasma prekallikrein, functional kallikrein inhibition capacity, spontaneous plasmin activity, plasminogen, functional antiplasmin activity, prothrombin and antithrombin-III were measured, using chromogenic peptide substrate assays before and during CPB as well as in the postoperative period. The antiplasmin activity decreased more in the dextran than in the Ringer group following cardiopulmonary bypass but the difference was without clinical significance. No statistically significant intergroup difference was found in the other measured variables of the kallikrein-kinin, fibrinolytic and coagulation systems.

Effects on Peritoneal Proteolysis and Hemodynamics of Prophylactic and Therapeutic Infusions of High Doses of Aprotinin in Experimental Acute Pancreatitis

Acute pancreatitis was induced in pigs by retrograde injection of Na-taurocholate into the pancreatic duct. Chromogenic peptide substrate assays showed increased trypsin (TRY) and plasma kallikrein activity (KK), parallel with a reduction of plasma prekallikrein (PKK) and functional kallikrein inhibition (KKI) values, in the peritoneal exudate in untreated animals. Intravenous high-dose pretreatment or therapy with aprotinin starting 3 h after the induction of acute pancreatitis resulted in significantly increased KKI capacity and unchanged KK and TRY activities in the peritoneal exudate. In test animals receiving aprotinin intravenously a significantly increased survival rate and improved cardiac output and arterial blood pressure were found during the 6-h observation period. All animals treated with aprotinin survived the observation period, whereas 63% of the untreated animals died. The study emphasizes the pathophysiological importance of the plasma kallikrein-kinin system in acute pancreatitis.

Plasma prekallikrein, functional kallikrein inhibition, antithrombin III, plasminogen, kallikrein activity and proenzyme functional inhibition index in 172 acute ill surgical patients on admission.

The present study was performed in order to study disturbances in plasma proteolysis in acute ill surgical patients on admission. The paper describes the distribution of values for plasma PKK, KKI, AT III, Plg, KK and PFI-index. In early stages of the disease process rather minimal information can be obtained by these data in addition to clinical examination. The study indicates that chromogenic peptide substrate assays should be reserved for surgical patients treated in the intensive care unit.

Evaluation of patients with acute pancreatitis by means of chromogenic peptide substrate assays and the proenzyme functional inhibition index.

Using chromogenic peptide substrate assays the severity and clinical course were evaluated in 37 patients with acute pancreatitis. Retrospective clinical evaluation revealed that 20 patients had a severe disease, whereas 17 patients had mild acute pancreatitis. Seven of the patients with severe acute pancreatitis died. The proenzyme functional inhibition index (PFI index) is defined as the sum of deviations from the normal plasma pool values of plasma prekallikrein, functional kallikrein inhibition, plasminogen, antiplasmin, prothrombin and antithrombin III. Increased values are counted as positive, whereas reductions compared with the normal plasma pool values are recognized as negative. During the second day after admission the PFI index revealed significantly more negative values in severe cases than in patients with mild acute pancreatitis, -159 in severe case, -74 in mild cases (median values, P less than 0.05). The PFI index values were maintained strongly negative for the following 3 days in severe cases whereas the index was brought to positive values during the same period in patients with mild acute pancreatitis. The fatal cases revealed strongly negative PFI index values for the whole observation period. The patients with severe acute pancreatitis were earlier identified by means of the PFI index than by individual parameters also used for calculating the index. The results show that by means of the PFI index severity of acute pancreatitis can be recognized during early stages of the disease.

Studies on the Plasma Kallikrein-Kinin System in Peritoneal Exudate and Plasma during Experimental Acute Pancreatitis in Pigs

Acute pancreatitis was induced in pigs by retrograde injection of Na-taurocholate into the pancreatic duct. By means of chromogenic peptide substrate assays, increased plasma kallikrein activity, parallel with a reduction of plasma prekallikrein and functional kallikrein inhibition values, was found in peritoneal exudate. In plasma, however, no changes in the kallikrein-kinin system were found during the 6-h observation time. The study demonstrates the presence of components of the plasma kallikrein-kinin system in peritoneal fluid and suggests that the peritoneal cavity to a great extent is a functionally separate compartment from plasma. Activation of the plasma kallikrein-kinin system in peritoneal exudate during acute experimental pancreatitis appears to be of importance for the initial symptoms and the development of shock seen during this condition.

Evaluation of severity and prognosis in early stages of septicemia by means of chromogenic peptide substrate assays.

Components of the plasma protease systems were determined by means of chromogenic peptide substrate assays during the early stage of septicemia in 21 patients of whom 11 died. The proenzyme functional inhibition index, calculated from the measured values for plasma prekallikrein, functional kallikrein inhibition, plasminogen and functional antiplasmin and antithrombin III activities, were markedly reduced in both groups, but significantly lower in the fatal cases than in the survivors from the first day of septicemia and throughout the observation period. Fatal septicemia thus appear to be associated with a more extensive proteolytic activity in plasma than nonfatal septicemia and can be readily disclosed by calculation of the proenzyme functional inhibition index.

Plasma kallikrein-kinin system in septicemia.

Plasma prekallikrein and functional kallikrein inhibition were studied in 18 surgical patients with complicating septicemia using chromogenic peptide substrate assays. Nine patients died and nine survived. In all 18 patients plasma prekallikrein values were reduced markedly when septicemia was diagnosed. During treatment gradually increasing values were found in the survivors, whereas values remained low in the fatal cases. Significantly reduced functional plasma kallikrein inhibition was associated with the development of fatal septic shock. The findings show that determination of these components of the plasma kallikrein-kinin system gives valuable information of prognostic value in patients with septicemia. Furthermore, the chromogenic peptide substrate assays used are fast and easy to perform and therefore suitable for intensive care medicine.