Possible physiological role of new peptide fragments released from bovine high molecular weight kininogen by plasma kallikrein

Bovine milk kininogen fragment 1.2 promotes the proliferation of osteoblastic MC3T3-E1 cells

The active component on the proliferation of osteoblastic MC3T3-E1 cells was purified and identified from bovine milk. The growth-promoting activity was measured by [(3)H]thymidine incorporation on the cell. The purified protein showed a molecular size of 17 kDa on SDS-PAGE. Its amino-terminal amino acid sequence was very similar to the internal sequence of bovine high molecular weight (HMW) kininogen, which comprises fragment 1.2. The promotion of proliferation was specific for osteoblastic MC3T3-E1 cells, not for fibroblast BALB/3T3 cells. In blood coagulation, HMW kininogen is considered to be cleaved by a specific enzyme kallikrein. HMW kininogen then releases two peptides, a biologically active peptide bradykinin and fragment 1.2, but the fate of fragment 1.2 is unknown. This milk-derived protein that comprises to fragment 1.2 showed a growth-promoting activity of osteoblasts. We propose the possibility that milk plays an important role in bone formation by supplying the active agent for osteoblasts as well as supplying calcium.

Studies on porcine high molecular weight kininogen. An improved method for the purification of porcine high molecular weight kininogen and cleavage of the kininogen by the action of porcine plasma kallikrein

By introduction of stepwise DEAE Sephadex A-50 and copper-Chelating Sepharose 6B column chromatographies, about 18.5 mg of high molecular weight kininogen (HK) composed of a single polypeptide chain was obtained from 500 ml of porcine plasma. Molecular weights of reduced or non-reduced preparation were estimated to be 110 kDa and 116 kDa, respectively, by SDS-PAGE. Using the preparation, cleavage of HK by porcine plasma kallikrein (KK) was investigated. A single polypeptide HK was cleaved into two chains cross-linked by disulfide bond(s), accompanying the release of kinin. Further degradation was not observed. Molecular weights of heavy-chain (H-chain) and light-chain (L-chain) were estimated to be 61 kDa and 56 kDa, respectively, by SDS-PAGE. The amino- (N-) terminal sequences of intact HK, reduced and carboxymethylated- (RCM-) H-chain, RCM-L-chain and the peptide around the kinin moiety obtained by BrCN digestion were determined. Their sequences were highly homologous with those of bovine or human HK. These results indicate that plasma KK first cleaved the Arg-Ser bond of HK, and formed nicked HK. The second cleavage yielded bradykinin (BK) and kinin-free protein, which was apparently of equal size to the nicked HK. The structure of HK was from the N-terminus to the carboxy- (C-) terminus, H-chain-BK-L-chain.

Kallikrein-kinin system in chronic subdural haematomas: its roles in vascular permeability and regulation of fibrinolysis and coagulation

The kallikrein-kinin system is closely related to both fibrinolysis and coagulation, and bradykinin--the end product of this system--is a powerful mediator which increases vascular permeability. In the present study, to test the hypothesis that the kallikrein-kinin system plays a part in the aetiology of chronic subdural haematomas, components of this system (prekallikrein, high molecular weight kininogen (HMW-kininogen), and bradykinin), and those of the fibrinolytic and coagulation systems were measured at 134 haematoma sites in 119 patients. The activities of prekallikrein and HMW-kininogen in the haematomas were significantly lower than those in the plasma of the patients, and showed a parallel decrease. The bradykinin concentration in the haematomas was significantly higher than that in the plasma. These results indicate activation of the kallikrein-kinin system in chronic subdural haematomas. The activation of both fibrinolysis and coagulation was also shown, and there was a significant correlation between HMW-kininogen and plasminogen, fibrin/fibrinogen degradation products, or platelets in the haematomas. This suggests regulation of fibrinolysis and coagulation by the kallikrein-kinin system or mutual stimulation of these systems. In the outer membrane, perivascular haemorrhage, interstitial oedema, and leucocyte migration were evident microscopically, indicating an increase in vascular permeability. The protein concentration in the haematomas was significantly higher than that in the peripheral blood, indicating plasma exudation from the capillaries in the outer membrane. The activation of the kallikrein-kinin system, by increasing vascular permeability, may cause blood extravasation and plasma exudation from the capillaries into both the outer membrane and the haematoma cavity, resulting in enlargement of the haematoma.

Inhibition of prekallikrein activation in human plasma by components of bovine plasma

Contact of plasma with a negatively charged surface activates prekallikrein and factor XII reciprocally. Activation of prekallikrein by several activators was impaired in bovine plasma when compared to that in human plasma. The activated partial thromboplastin time of bovine plasma, induced by several activators, was significantly longer than that of human plasma. Cleavage of [125I]factor XII was optimum at 10 min in human plasma but took up to 60 min in bovine plasma. Addition of bovine plasma to human plasma caused significant inhibition of dextran sulfate-induced prekallikrein activation, indicating that the impaired rate of contact activation in bovine plasma is due to the presence of inhibitors. The inhibitory effect was greater at lower concentrations of dextran sulfate but could not be abolished by increasing the concentration. The inhibitory activity eluted in two peaks at low and medium salt concentrations on carboxymethyl ion-exchange chromatography of bovine plasma.

Prekallikrein activation in human, bovine, and rabbit plasmas: presence of an inhibitor in bovine plasma

Contact of human plasma with a negatively charged surface such as dextran sulfate activates prekallikrein to kallikrein, which releases the vasoactive peptide bradykinin from high-molecular-weight kininogen. The dextran sulfate-induced activation of prekallikrein at 0 degree C (assayed by its amidolytic activity on the chromogenic substate S-2302) could not be observed in either bovine or rabbit plasmas when compared to human plasma. Neither bovine nor rabbit plasma inhibited the amidolytic activity of contact-activated human plasma at 0 degrees C. The activation of prekallikrein in human plasma was significantly inhibited by the addition of bovine plasma but not by rabbit plasma. Bovine plasma (0.025 units, 1 unit = 1 ml of plasma) caused 68.8% inhibition of prekallikrein activation. Eighty percent of the inhibitory property of bovine plasma was present in the greater than 30,000-molecular-weight fraction. These results indicate the presence of an inhibitor(s) of prekallikrein activation in bovine plasma.

Comparison of the rat liver microsomal metabolism of the enantiomers of warfarin and 4'-nitrowarfarin (acenocoumarol)

1. Rat liver microsomal metabolism of the enantiomers of warfarin and acenocoumarol (4'-nitrowarfarin) has been studied. The enantiomers of both compounds were hydroxylated mainly at the 6- and 7-positions. Acenocoumarol enantiomers were much better substrates for cytochromes P-450 than the corresponding warfarin enantiomers; Km values for the 6- and 7-hydroxylations were 2 to 19 times lower for R- and S-acenocoumarol than for warfarin. 2. Formation of the 6-, 7-, and 8-hydroxy-metabolites of warfarin was stereoselective for the R-enantiomer (the R/S ratio for total intrinsic clearance was about 3). 4'-Hydroxylation was not stereoselective. In contrast, formation of acenocoumarol metabolites was stereoselective for the S-enantiomer (the S/R ratio for total intrinsic clearance was about 3). 3. From the effects of phenobarbitone and methylcholanthrene induction, and inhibition by cimetidine, on in vitro metabolism of the enantiomers of both compounds, it was concluded that the differences between warfarin and acenocoumarol can be explained partly by the involvement of different enzymes.

Effect of glutathione depletion on aminopyrine and formaldehyde metabolism

In previous studies, diethylmaleate (DEM)- and phorone-induced hepatic glutathione (GSH) depletion in rats was accompanied by impaired evolution of 14CO2 from the N-14C-labeled methyl groups of aminopyrine, which in turn was attributed to impaired generation of formaldehyde, its subsequent oxidation to formate, or to some combination of both. In the present study, l-buthionine sulfoximine (BSO)-induced hepatic GSH depletion was also accompanied by decreased evolution of CO2 from aminopyrine, but the extent of the fall in CO2 was less than that induced by DEM or phorone, even though the decrease in hepatic GSH was comparable with all three GSH-lowering compounds. Incubation of freshly prepared normal hepatic microsomes in vitro with the GSH-lowering agents resulted in impaired aminopyrine-N-demethylase (APDM) activity with inhibition by phorone greater than DEM greater than BSO. By contrast, hepatic microsomes prepared from rats pretreated with these compounds had normal APDM activity. 14CO2 evolution from i.p. administered [14C]formaldehyde was not impaired by any of the GSH-lowering compounds. Thus, assessment of APDM activity and formaldehyde metabolism did not unequivocally establish the mechanism(s) by which CO2 evolution from aminopyrine is depressed by DEM, phorone and BSO, although low GSH is likely to impair metabolism of formaldehyde formed in liver after demethylation of aminopyrine. Quantitative differences in the degree of depression of CO2 evolution suggest that at least DEM and phorone exert an additional inhibitory effect by a GSH-independent mechanism. This may involve inhibition of aminopyrine-N-demethylase activity.

Isolation of a cationic fragment of high molecular mass kininogen and effect of this fragment on human plasma kallikrein activity

The effect of a cationic fragment of high molecular mass (HMM) kininogen on kallikrein activity and the autocatalytic process of prekallikrein-to-kallikrein conversion were studied. Prekallikrein and kallikrein were obtained by ion exchange and affinity chromatography; the purification of HMM kininogen was achieved using QAE- and DEAE-Sephadex, and separation of the cationic fragment was carried out by gel filtration. It was shown that the fragment of HMM kininogen (mol. mass. 7000, high lysine content) suppressed the activity of a labile form of kallikrein and prevented activation of prekallikrein. A model of the prekallikrein-kallikrein system is proposed. The model is based on the recently established fact of occurrence of two kallikreins and two kallikrein precursors. It involves formation from kininogen, besides kinins, of a kallikrein inhibitor.

Chlordecone-induced hepatic dysfunction

Chlordecone (Kepone) is a decachloroketone analog of the dodecachlorohydrocarbon mirex and is used as a stomach poison insecticide. Despite the structural similarity to mirex, chlordecone is unlike mirex in general organ-specific toxic properties. Chlordecone is primarily accumulated in the liver, where it causes a variety of morphological and biochemical alterations. Although less effective than mirex as a hepatotoxin, it causes liver enlargement, focal necrosis, mitochondrial changes, fatty infiltration of hepatocytes, and proliferation of endoplasmic reticulum. Chlordecone accumulation and morphological alterations in the liver were also observed in occupationally exposed human patients. Induction of hepatic microsomal mixed-function oxidases (MFOs) and impaired production and utilization of hepatocellular energy are the principal biochemical aberrations produced by chlordecone. Chronic exposure causes carcinogenesis in mice and rats. Hyperplastic nodules, which progress to hepatocellular carcinomas, are the principal pathological lesions. Acute and chronic exposures to chlordecone result in hepatobiliary dysfunction manifested as impaired excretion of anionic compounds accompanied by choleresis. Exposure to chlordecone results of greatly potentiated haloalkane hepatotoxicity, representing a most potent toxic interaction at otherwise individually nontoxic levels. In view of the demonstrated carcinogenic effect of chlordecone, such interactions at very low levels assume extraordinary significance in terms of chronic toxicological and pathological manifestations induced by combinations of toxic chemicals.

Occurrence of Leu-Lys-bradykinin and histidine-rich peptide in high-molecular-weight kininogen isolated from horse plasma

On incubation of purified horse plasma high-molecular-weight kininogen with purified plasma kallikrein, three new peptides, named fragment 1.2, fragment 1 and fragment 2, were released, in addition to the vasopeptide, bradykinin. Fragment 2 contained an extremely high level of histidine, in which eleven residues out of the total 48 residues were characterized. Thus the result proves the existence of the histidine-rich region in horse high-molecular-weight kininogen, which is similar to the region previously identified in bovine high-molecular-weight kininogen. Moreover, we have identified a new kinin derivative, Leu-Lys-bradykinin, in horse high-molecular-weight kininogen.

The effects of ureteral occlusion and renal venous constriction on kidney kallikrein-kinin and prostaglandin systems in dogs

The intrarenal pressure was raised to 40--50 mmHg by ureteral occlusion or by renal venous constriction in anesthetized dogs loaded with 10% mannitol in saline and with a urine flow of approximately 1 ml/min/kidney. Both manoeuvres produced vasodilation and decreased urine creatinine excretion (GFR). Ureteral occlusion was associated with a marked antinatriuresis, which contrasted the variable decrements in sodium excretion during renal venous constriction. Ureteral occlusion did not affect urine excretion of kallikrein or kinins, whilst renal venous constriction decreased urinary kallikrein excretion, yet markedly increased urinary kinin excretion. Ureteral occlusion and renal venous constriction comparably increased urine prostaglandin (E-like) excretion by a presumably pressure dependent mechanism. Inhibition of prostaglandin synthesis by indomethacin abolished the vasodilation during renal venous constriction and this was accompanied by marked reductions of urinary creatinine (GFR) and kallikrein excretions, whilst the kinin excretion was enhanced as observed before the administration of indomethacin.