Mechanism and significance of kinin formation in nephrotic syndrome.

There were few reports demonstrating behavior of kinin and kininogen in the nephrotic syndrome. In this paper, coagulation factors related to contact activation, such as factor XII (FXII), factor XI (FXI), prekallikrein (PK), high molecular weight kininogen (HMWKG), and kinins were measured in 15 cases of nephrotic syndrome, and clinical significance of these results were discussed. Plasma FXII activity was markedly decreased in the onset and florid stages of nephrotic syndrome, and this decrease was not correlated with plasma albumin level, which suggested marked activation of this factor in these stages. However, the decrease of PK was slight at the above stages. Activations of contact factors were not parallely occurred with the marked consumption of FXII. Plasma kinin activity was not increased in the onset and critical stages of the nephrotic syndrome but increased in the convalescent and chronic stages, while HMWK level was maintained higher than normal throughout the course. Plasma angiotensin-converting enzyme (kininase II) activity was increased in the early stage and decreased lower than normal during the course of the disease. It was concluded that kinin formation in the nephrotic syndrome was not due to the activation of intrinsic coagulation system but due to release of kinin from low molecular weight kininogen. This increased level of kinin activity in convalescent and chronic stage may be related to the healing process during the course of this syndrome. Low kinin activity in the early stage of this disease might be also explained by increased kininase II activity.

Clotting activities and antigen concentrations of contact factors in kidney disease.

Factor XII, prekallikrein (PK) and high molecular weight kininogen (HMWK) clotting activities and antigen concentrations in kidney disease patients were studied. Chronic hemodialysis led to a reduction of F XII, PK and HMWK clotting activities. F XII and PK antigen levels were also low. In contrast, the HMWK antigen was normal with respect to concentration as well as electrophoretic migration behaviour on 2 D-immunelectrophoresis. In kidney transplant recipients more than three month after the transplantation, we found an increased of F XII and PK clotting activities, which appeared to depend on the time elapsed since the operation. However, the antigen levels remained normal. The group of chronic kidney disease patients not requiring hemodialysis exhibited normal mean values of all three clotting activities as well as normal F XII and HMWK antigen levels. The PK antigen was reduced. However, a separate evaluation of F XII clotting activities (F XII:C) in patients with glomerular nephritis showed elevated F XII:C which correlated with the BUN values. During acute processes of the kidney disease we observed very high PK clotting activities, which normalized with stabilization of the patients. Our results show that the contact phase coagulation factors behave abnormally in certain kidney disease patients.

Activation of factor XII-dependent pathways in human plasma by hematin and protoporphyrin.

Intravenous administration of hematin is effective in the treatment of acute exacerbations of the inducible porphyrias. In the course of such treatment, coagulopathies have occurred that are characterized by prolongation of prothrombin time, partial thromboplastin time, and formation of fibrin split products. In experiments in vitro with normal human plasma, we observed that hematin and protoporphyrin activated Factor XII-dependent pathways of coagulation and fibrinolysis, and that they generated kallikrein activity. Incubation of protoporphyrin with purified Factor XII resulted in activation as measured by amidolysis of a chromogenic substrate. Neither coproporphyrin, uroporphyrin, delta-aminolevulinic acid, porphobilinogen, or bilirubin activated Factor XII-dependent pathways. Exposure of serum containing added uroporphyrin, coproporphyrin, and protoporphyrin, but not hematin, to ultraviolet light (405 nm) resulted in activation of the classical pathway of the complement system. On the other hand, exposure of plasma containing uroporphyrin or coproporphyrin to ultraviolet light did not result in activation of Factor XII-dependent pathways.

Immunoreactive tissue kallikrein in human serum.

Human urinary kallikrein and an antiserum to it raised in the rabbit were used to detect and quantitate immunoreactive tissue kallikrein in human serum. Both 125I-labeled kallikrein and the unlabeled purified enzyme appear complexed to higher molecular weight entities in serum, but specific binding between radiolabeled enzyme and antiserum was unaffected by the presence of serum or plasma. Parallelism to standard displacement curves was always seen with radioimmunoassay of normal sera as well as with human mixed saliva or pancreatic extracts. Assay sensitivity is 160 pg/ml of serum, or 16 pg per tube. Purified plasma kallikrein or prekallikrein in concentrations up to 10 micrograms/ml showed no displacement. Acetone-kaolin activation of plasma produced the expected 30-fold increase in Tos-Arg-OMe esterase activity but no change in immunoreactive tissue kallikrein levels. Serum concentrations were 3.8 +/- 0.7 (mean +/- SE) ng/ml in 21 normal volunteers, and were similar in patients with Fletcher trait or Hageman factor deficiency. Significantly increased serum concentrations were seen with long-term low dietary sodium intake or acute forms of pancreatitis. Although the relation of this immunoreactive material to any active tissue kallikrein within the circulation remains to be determined, our studies provide a new parameter for the assessment of a system repeatedly suggested to have some role in regulation of vascular resistance.

Studies of the kallikrein-kinin system in patients with sickle cell anemia.

Eight patients with sickle cell anemia (SS hemoglobin) were found to have decreased plasma levels of prekallikrein compared to normal control subjects or patients with other types of anemia. The prekallikrein levels in the patients with sickle cell anemia were found to decrease further during a sickle cell crisis. These results suggest that components of the kallikrein-kinin system are profoundly affected in patients with sickle cell anemia, and during crises may play a role in the clinical presentation of patients.

Activation of factor XII in rat plasma: protection by benzamidine of the cofactor function of high molecular weight kininogen.

Factor XII has been assayed as kaolin-activated prekallikrein activator in rat citrated plasma pretreated with acetone (Briseid et al. 1978 & 1979; Briseid & Berstad 1979). In the present work benzamidine added during blood collection increased the extent of activation by a factor of 6. Rat high molecular weight kininogen (HMWK) added to acetone-treated citrated plasma likewise increased the activation, providing evidence of the protection by benzamidine of the cofactor function of HMWK. All cofactor capacity was retained after the removal of the kinin part of HMWK. Experiments carried out with plasminogen-free plasma showed that plasmin could hardly be the the factor responsible for the destruction of HMWK. The stoichiometric factor XII concentration-effect curve obtained by diluting acetone-treated rat plasma with acetone-treated human factor XII deficient plasma showed that factor XII is present in functional excess, the concentration of HMWK deciding the extent of activation. By diluting acetone-treated rat plasma with buffer, HMWK concentration-effect curves were obtained which were approximately linear over a range of 0.03-0.40 microgram (bradykinin equivalents) per ml kaolin incubate. No further activation of factor XII was obtained at 0.80 microgram/ml.

Effect of serotonin antagonists on the dextran-induced anaphylactoid reaction in the rat.

Dextran injected intravenously into rats causes a rapid lowering of the extent of activation of factor XII and of the plasma levels of prekallikrein and plasminogen, and at the same time a profound fall in blood pressure. The effects on these dextran-induced reactions of three serotonin antagonistic lysergic acid derivatives were studied in the rat: bromolysergic acid diethylamide (BOL 148), methysergide, and ergotamine. BOL 148 was found to be the only effective inhibitor of the blood pressure fall, possessing an inhibitory effect over the dose range 1.0-4.0 mg/kg intravenously. The finding supports the assumption that part of the dextran-induced blood pressure fall is mediated by serotonin through D-receptors. All three serotonin antagonists showed a serotonin-like lowering effect on the activation of factor XII and on the level of prekallikrein in plasma (BOL 148 1.0-4.0 mg/kg; methysergide 0.10-0.60 mg/kg; ergotamine 0.10-0.60 mg/kg). The results with the serotonin antagonist alone and in combination with dextran provided evidence that the serotonin-mediated part of the blood pressure fall can not be secondary to the effect of dextran on the plasma parameters assayed.

Kinetics of activation of prekallikrein by prekallikrein activator.

A 28 000 molecular weight activator of prekallikrein was isolated from human plasma, and the kinetics of its enzymic activity toward prekallikrein was investigated. The activation follows Michaelis-Menten kinetics with a kcat of approximately 3 S(-1); Km is strongly dependent upon the ionic strength. Under suitable conditions the activation obeys first-order kinetics, and the first-order rate constant may be used to quantitate prekallikrein activator activity. Thus a two-stage assay, in which the first step involves the activation of prekallikrein by the activator and the second step quantitates the kallikrein generated, was developed to allow the measurement of prekallikrein activator in biologic samples. The prekallikrein activator content of therapeutic protein solutions, as determined by means of this assay, correlated well with the hypotensive activity of these solutions as determined in an animal model.