Effectors of the activation of human [Glu1]plasminogen by human tissue plasminogen activator

The activation of human [Glu1]plasminogen [( Glu1]Pg) by human recombinant (rec) two-chain tissue plasminogen activator (t-PA) is inhibited by Cl-, at physiological concentrations, and stimulated by epsilon-aminocaproic acid (EACA), as well as fibrin(ogen). Chloride functions as a result of its binding to [Glu1]Pg, with a Ki of approximately 9.0 mM, thereby rendering [Glu1]Pg a less effective substrate for two-chain rec-t-PA. EACA stimulates the activation in Cl-(-)containing solutions, with a Ka of approximately 4.0 mM, primarily by reversal of the Cl-(-)inhibitory effect. Fibrinogen appears to exert its stimulatory properties mainly through effects on the enzyme, two-chain rec-t-PA, with a Ka of approximately 3.7 microM in activation systems containing physiological levels of Cl-. Analysis of the results of this paper reveals that normal plasma components, Cl- and fibrinogen, exert major regulatory roles on the ability of [Glu1]Pg to be activated by two-chain rec-t-PA, in in vitro systems. The presence of Cl- inhibits the stimulation of [Glu1]Pg activation that would normally occur in the presence of fibrinogen, a result of possible importance to the observation that some degree of systemic fibrinogenolysis accompanies therapeutic use of tissue plasminogen activator.

Plasminogen receptors, urokinase receptors, and their modulation on human endothelial cells

Endothelial cells are centrally involved in regulation of fibrinolysis, and receptors for plasminogen and urokinase provide a mechanism by which cells can regulate their fibrinolytic function. Therefore, the existence and characteristics of receptors for these fibrinolytic components on cultured human umbilical vein endothelial cells were examined. We verified the presence of plasminogen receptors on these cells (Kd = 2.1 +/- 1.3 mumol/L, and 1.8 +/- 1.3 x 10(7) binding sites/cell). These binding parameters and other characteristics indicate that these receptors are closely related to the plasminogen receptors on many circulating and adherent cells. Specific binding sites that interact with two-chain urokinase of mol wt 55,000 with a dissociation constant of 2.1 +/- 1.7 nmol/L, with 2.9 +/- 2.9 x 10(5) sites/cell were also identified. Single-chain urokinase of mol wt 55,000, but not the two-chain degradation product of mol wt 33,000 bound to the cells, implicating the amino-terminal aspects of the ligand in receptor recognition. When endothelial cells were stimulated with thrombin, an agent that modulates their fibrinolytic potential, both receptor types were modestly affected; urokinase binding increased 17%, whereas plasminogen binding decreased 19%. The presence and modulation of plasminogen and urokinase receptors provide a potentially important additional mechanism by which endothelial cells may regulate fibrinolysis.

Effects of zinc acexamate on gastric mucosal production of prostaglandin E2 in normal and stressed rats

Changes in PGE2 levels induced by zinc acexamate (ZAC) at gastricmucosal level were assessed in a rat model. Experiments were performed in normal rats and rats subjected to cold-restraint stress and in experimental conditions in which prostaglandins (PGs) synthesis was inhibited by prior administration of indomethacin. Gastric injuries after different treatments were quantified macro and microscopically. Total amount of PGE2 and mucus material recovered from gastric mucosa were increased after ZAC treatment. Indomethacin aggravated gastric damage secondary to stress and inhibited PGE2 and mucus increase appearing after ZAC treatment. These data confirm the relation between PGE2, mucus production and gastric protection. ZAC 200 mg/kg was able to reduce the gastric damage induced by stress. This decrease was also evident in the group receiving indomethacin before ZAC administration. These experiments indicate that ZAC exhibits its antiulcer action by increasing prostaglandins but other mechanisms independent of PGs synthesis are also involved.

The relationship between inhibition of plasminogen-activator activity and prostatic involution

The role of plasminogen activators (PAs) as potential mediators of involution of the rat ventral prostate was investigated by using an approach involving the administration in vivo of anti-PA drugs. The prostates of castrated rats, which had been injected daily for 7 days with the anti-PA drugs 6-aminohexanoic acid, tranexamic acid, aprotinin and cortisol, were assayed for PA activity, weight and cell number. In the prostates from the castrated controls, there was a 10-fold increase in the mean PA activity and a 7-fold decrease in cell number relative to that of the non-castrated animals. Although this rise in enzyme activity could be decreased to some extent by all the drugs except aprotinin, only treatment with high doses of tranexamic acid or cortisol had a statistically significant effect. A similar pattern was observed with respect to the relative potency of the drugs in preventing the loss of prostatic weight and cell number after castration. The effects of cortisol were dose-dependent, with complete inhibition of both the rise in PA activity and cell loss occurring at a dose of about 15 mg/day. Since the concentration of the principal intranuclear androgen, dihydrotestosterone, was the same in the prostates from treated and untreated castrated rats, the effects of cortisol are not due to increased retention of this androgen. Rather, the high inverse correlation (r = 0.86) between the cellular concentration of PA activity and the cell population of the prostate implies that PAs are directly associated with prostatic involution and that cortisol, and to a lesser extent tranexamic acid, blocks the involution process through inhibition of PAs.

Follicular development is impaired by inhibitors of serine proteases in the rat

Serine proteases such as plasminogen activators are produced by granulosa cells both in vivo and in vitro and have been implicated in the process of ovulation. For a study of potential roles of serine proteases in early follicular development, immature rats were injected with pregnant mare serum gonadotropin, followed 2 hours later by laparotomy and injection of the serine protease inhibitors benzamidine and epsilon-aminocaproic acid into the bursa of one ovary. As a control, saline solution was injected into the contralateral bursa. Animals were put to death 48 hours after injection of serine protease inhibitors, and three to five randomly selected longitudinal sections were evaluated by computerized morphometry. The area occupied by antral follicles relative to the total cross-sectional area of each section was computed. Resultant ratios from serine protease inhibitor-treated ovaries were compared with those from contralateral control ovaries. Ninety-three percent of serine protease inhibitor-treated ovaries showed a reduction in antral follicular size when compared with corresponding control ovaries, which is indicative of inhibitory effects of serine protease inhibitor treatment on folliculogenesis. To further investigate this effect, ovulation was induced by human chorionic gonadotropin administration 48 hours after pregnant mare serum gonadotropin and 46 hours after serine protease inhibitor or saline solution treatment. Animals were put to death 20 hours later and the number of oocytes ovulated into oviducts was determined. Oviducts from serine protease inhibitor-treated ovaries contained 51% fewer oocytes than their control counterparts. Artifacts of surgical stress or vascular diffusion of serine protease inhibitor from treated to control sides were ruled out by appropriate control experiments. We conclude that early serine protease inhibitor treatment of pregnant mare serum gonadotropin-stimulated rat ovaries impairs folliculogenesis. Thus, in addition to involvement in ovulation, serine proteases appear to play important roles throughout follicular development.

Resistance of mice to reinfection after E-aminocaproic acid treatment of primary influenza virus infection

The effect of proteolysis inhibitors on the formation of resistance to virus challenge has been studied in experimental influenza of mice. E-aminocaproic acid (E-ACA) when used in the treatment of influenza decreased the virus reproduction in lungs and also enhanced the humoral immune response. The antibody titre on days 14 to 21 post infection (p.i.) was significantly higher in the treated animals. On day 30 after challenge with the homologous strain (H3N2) the virus reproduced to low levels in the lungs of untreated convalescent mice, but no virus was detected in the lungs of mice which had been treated with E-ACA during primary infection. Marked increase of the antibody level was found in such mice. Upon challenge with lethal doses of the virulent strain (H1N1), the protection was significantly higher among animals treated with E-ACA during primary infection with a sublethal virus dose. We believe that the immunomodulatory action of E-ACA may play an important role in the increased resistance to challenge exhibited by such treatment.

Control of human plasminogen activation

The activation of Glu1-plasminogen (Glu-Pg) by streptokinase (SK), urokinase (UK) and tissue plasminogen activator (tPA) is under rigorous control by molecules such as epsilon-aminocaproic acid (EACA), fibrinogen (Fg), fibrin (Fn) and, as we have recently discovered, anions. This presentation will focus on the biochemical mechanisms that are involved in these processes. In the case of activation by SK, a species of activator complex, composed of Glu-Pg and SK, can be identified that is inhibited by anions, such as Cl-, and stimulated by Fg and Fn. This species rapidly decays to another activator complex, also consisting of Glu-Pg and SK, that is much less sensitive to control by these effector molecules. The most stable activator complex, containing equimolar SK and plasmin, is not affected to a great extent by anions, Fg or Fn. In the overall activation of Glu-Pg by SK, Cl- behaves as a mixed inhibitor, with a Ki of 6.4-9.2 mM, and Fg functions as a mixed activator, displaying a Ka of 110-240 nM. These results show that activation of Glu-Pg by SK in physiological samples would be considerably inhibited by Cl- in the absence of Fg. The activation of Glu-Pg by both high- and low-molecular weight UK is also inhibited by Cl-, but is stimulated by EACA. The inhibition by Cl- does not occur in the presence of concentrations of EACA that saturate its weak binding sites on Glu-Pg, and the stimulation by EACA is maximally exhibited in the presence of Cl-.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetic studies on the effect of heparin and fibrin on plasminogen activators

1. Possible interactions between fibrin(ogen) and heparin in the control of plasminogen activation were studied in model systems using the thrombolytic agents tissue-type plasminogen activator (t-PA), urokinase and streptokinase.plasminogen activator complex and the substrates Glu- and Lys-plasminogen. 2. Both t-PA and urokinase activities were promoted by heparin and by pentosan polysulphate, but not by chondroitin sulphate or hyaluronic acid. The effect was on Km. 3. In the presence of soluble fibrin (and its mimic, CNBr-digested fibrinogen) the effect of heparin on t-PA was attenuated, although not abolished. In studies using a monoclonal antibody and 6-aminohexanoic acid, it was found that heparin and fibrin did not seem to share a binding site on t-PA. 4. The activity of t-PA B-chain was unaffected by heparin, so the binding site is located on the A-chain of t-PA (and urokinase). 5. Fibrin potentiated the activity of heparin on urokinase. The activity of streptokinase.plasminogen was unaffected by heparin whether or not fibrin was present. 6. If these influences of heparin and fibrin also occur in vivo, then, in the presence of heparin, the relative fibrin enhancement of t-PA will be diminished and the likelihood of systemic activation by t-PA is increased.

Effect of cold-restraint stress and zinc acexamate on gastric mucus production in intact glands

Gastric mucus content was morphometrically evaluated in gastric glands of normal and cold-restraint stressed rats. Variations induced by treatment with zinc acexamate (200 mg/kg p.o.) were also investigated. Stress decreased the glycoprotein content in glands located in areas of injury. However, in intact glands from the same animals, the glycoprotein content was increased and the proportion of sulphated macromolecules greatly augmented. Zinc acexamate reduced the severity of damage in stressed rats. Although it augmented mucus content it prevented the modification in sulphated macromolecules in these rats. These findings are discussed in relation to the role of gastric mucus in preventing gastric damage.

Effects of simultaneous treatment with various chemicals on BHA-induced development of rat forestomach hyperplasia--complete inhibition by diethylmaleate in a 5-week feeding study

Male F344 rats were administered phenobarbital, polychlorinated biphenyl (PCB), retinol acetate, indomethacin, 6-amino-caproic acid, dexamethasone (DEX) or diethylmaleate (DEM) for one week and then were treated with these chemicals plus butylated hydroxyanisole (BHA) for a further four weeks. Histopathologically, the incidence of BHA-induced forestomach hyperplasia was significantly lower in rats treated with PCB, DEX or DEM than in those treated with BHA alone. However, the inhibition by PCB and DEX was only partial and might have been due to decreased food intake. On the other hand, DEM completely inhibited the hyperplastic response to BHA at a dose of 0.25%, and even at lower doses it demonstrated significant inhibition without any decrease in body weight or food intake. The result that DEM, a tissue glutathione depleting agent, can inhibit BHA-associated forestomach hyperplasia strongly suggests that tissue glutathione may be intimately involved in the induction of forestomach hyperplasia by the antioxidant in rats.

Autologous fibrin tissue adhesive biodegration and systemic effects

A series of experiments was conducted to investigate the rate of Autologous Fibrin Tissue Adhesive (AFTA) degradation by the fibrinolysis inhibitor, epsilon amino caproic acid (EACA). The duration of AFTA clots in vitro, subcutaneous, and in the middle ear was prolonged for a time interval that was proportional to the concentration of EACA in Component II of the adhesive. No toxic reactions were observed in the middle or inner ear. Systemic pathology (thrombosis or emboli) could not be related to the presence of EACA applied in the middle ear or directly into the blood stream at concentrations (mg/kg body weight) up to 1,500 times that expected to occur during surgery on humans.

Phorbol ester induces cultured endothelial cells to invade a fibrin matrix in the presence of fibrinolytic inhibitors

We have previously shown that the tumor promoter 4 beta-phorbol 12-myristate 13-acetate (PMA) induces capillary endothelial cells grown to confluency on the surface of three-dimensional collagen gels to invade the underlying matrix and to form capillary-like tubular structures, a phenomenon mimicking angiogenic processes that occur in vivo (Montesano and Orci: Cell, 42:469-477, 1985). Since angiogenesis frequently occurs within a fibrin-rich extracellular matrix, we have examined the ability of PMA-treated endothelial cells to invade fibrin gels. Control endothelial cells grown on fibrin gels formed a confluent monolayer on the gel surface and did not invade the underlying matrix. Treatment of the cultures with PMA resulted in a progressive lysis of the substrate without invasion of the fibrin matrix. However, if the cells were treated with PMA either in the presence of fibrinolytic inhibitors (Trasylol, epsilon-aminocaproic acid) or in the absence of detectable plasminogen, dissolution of the substrate was prevented, and the endothelial cells invaded the fibrin gel, forming vessel-like tubular structures similar to those previously observed with collagen gels. These results demonstrate that the invasive and morphogenetic events induced by PMA do not necessarily require an interaction between endothelial cells and collagen fibrils but can also occur with other biologically relevant substrata. They also suggest (1) that invasion may occur via a plasmin-independent mechanism and (2) that in vivo, neutralization of excess proteolytic activity may play an important permissive role in angiogenesis and other invasive processes by preventing uncontrolled matrix degradation.

Role of plasminogen, plasmin, and plasminogen activators in the migration of fibroblasts into plasma clots

Human diploid fibroblasts were seeded onto or into plasma clots and different aspects of cell adhesion and migration were measured. The roles of plasminogen activators and plasmin were studied by either the removal of plasminogen from plasma prior to clotting or by the addition of 10 mM epsilon-aminocaproic acid, which brings about an inhibition of plasmin in this system. When cells were seeded onto the surface of plasma clots, rates of attachment, spreading, and migration were unaffected by plasminogen depletion or plasmin inhibition. In contrast, when cells were seeded into plasma clots, then, although the rates of cells spreading were unaffected, cell migration was abolished by plasminogen depletion or by plasmin inhibition. When cells were seeded onto the surface of plasma clots and the rate of migration into the clots was measured, there was an absolute requirement for plasmin activity; while fibroblasts migrated rapidly into the fibrin lattice of control clots, in the case of plasminogen-depleted clots, cells failed to penetrate the lattice. Focussing through a plasma clot revealed that fibroblasts do not migrate through the fibrin lattice but instead, localized areas of fibrinolysis are generated and cells migrate over the surface of the area of lysis.

Endothelial linings: the effect of serine protease inhibition

The purpose of this investigation was to determine if the inhibition of the serine proteases, thrombin and plasmin, by heparin and epsilon-aminocaproic acid (EACA) would improve endothelial cell retention on synthetic grafts. Endothelium was harvested from the external jugular veins of mongrel dogs using an enzymatic technique. The cells were grown in tissue culture for 3-4 weeks, labeled with 111In oxine, inoculated (2000 cells/mm2) into fibronectin-coated 4 mm-diameter tubes of polyester elastomer (PE, Hytrel 4056, DuPont), and cultured for 18 hr. Each animal received iv heparin (100 U/kg) prior to implantation, and a 4 X 30-mm segment of the culture-lined PE was interposed in the dog's own carotid artery. After 6 hr of flow the grafts were perfusion fixed; the percentage of endothelial retention was determined by 111In counting, and the surfaces of the grafts were analyzed by scanning electron microscopy. Six experiments were performed in each of three treatment groups. Animals in Group I received no additional drugs. Group II animals received a continuous infusion of heparin at 30 U/kg/hr. Group III animals received a bolus of 200 mg/kg of EACA with the initial heparin dose and a continuous infusion of heparin at 30 U/kg/hr and EACA at 200 mg/kg/hr. Group I grafts retained an average of 36.1 +/- 23.3% of the cells; Group II retained 67.5 +/- 24.9%; and Group III retained 83.4 +/- 9.8%. Although continuous heparin infusion resulted in a trend (P = 0.067) toward better retention, a combined infusion of heparin and EACA resulted in significantly better retention (P = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of H-ras oncogene transformation of NIH3T3 cells by protease inhibitors

The protease inhibitors antipain, leupeptin, alpha 1-antitrypsin, and epsilon-aminocaproic acid were found to inhibit transformation of NIH3T3 cells after transfection with an activated H-ras oncogene. Inhibition of focus formation by protease inhibitors was concentration dependent and maximal at 50% of control values. Transfection of a gene for neomycin resistance was not affected by protease inhibitors. Antipain was inactive if present only during the first 2 days of the gene transfer protocol or only during the final 10 days of the experiment. However, the full effect was observed when antipain was added at the subculture step on day 3 and during the subsequent cell proliferation. If cells were not subcultured, the yield of the foci per microgram of DNA was sharply reduced and addition of antipain did not further suppress the transformation rate. Subculture of NIH3T3 cells 3 days after transfection at lower cell densities resulted in higher transformation efficiency. The results suggest that transformation of NIH3T3 cells by a single mutated oncogene may involve multiple stages including cell proliferation and that part of this process is susceptible to inhibition by protease inhibitors.

The reciprocal effects of epsilon-aminohexanoic acid and chloride ion on the activation of human [Glu1]plasminogen by human urokinase

The activation of human [Glu1]plasminogen [( Glu1]Pg) by high-molecular-weight two-chain human urinary urokinase [EC 3.4.21.31) and low-molecular-weight two-chain human urinary urokinase is inhibited by Cl- at physiological concentrations and stimulated by epsilon-aminohexanoic acid (epsilon Ahx; epsilon-aminocaproic acid). The inhibition by Cl- does not occur in the presence of concentrations of epsilon Ahx that saturate the acid's weak binding sites on [Glu1]Pg, and the stimulation by epsilon Ahx is maximally exhibited in the presence of Cl-. We have used intrinsic fluorescence measurements with [Glu1]Pg to show that the conformational alteration and the concomitant increase in activation rate that accompanies epsilon Ahx-binding to [Glu1]Pg in the presence of Cl- does not occur in the same manner without Cl-. Further, the decrease in the intrinsic fluorescence that is attendant to Cl- binding to [Glu1]Pg in the absence of epsilon Ahx is not observed in the presence of this effector molecule. Analyses of the results of this manuscript strongly indicate that a conformation of [Glu1]Pg that is not optimal for its activation by urokinase is adopted in the presence of Cl-, and this is relieved by epsilon Ahx. This has important implications in the inhibition of [Glu1]Pg activation in the solution phase of blood plasma and in the large acceleration of this process when plasminogen is bound to physiological positive effectors via its epsilon Ahx-binding site(s).

[Epsilon-aminocaproic acid inhibits the propagation of damage along the nerve fiber]

An inhibitor of proteinases--epsilon-aminocaproic acid--inhibits the propagation of destruction along the muscle fiber isolated from frog m. iliofibularis. It is assumed that generalization of the injury is hampered by a protein precipitate formed at the site of the injury, which is preserved due to inhibition of proteinase activity.

[Suppression of rotavirus SA-11 reproduction by protease inhibitors in cell culture]

The effect of proteases inhibitors, epsilon-amino-caproic acid and gordox, on reproduction of rotavirus SA-11 in MA-104 cells was studied by enzyme immunoassay. These inhibitors were shown to exert an inhibiting effect on rotavirus reproduction.

Comparison of the anti-inflammatory activity of sodium acexamate and zinc acexamate in healing skin wounds in rabbits

After obtaining an abscess on the inner thigh of rabbits, the resulting inflammatory area was treated with sodium acexamate and zinc acexamate (0.5 ml s.c. of a 7% w/v solution). All animals received labeled leukocytes (111In, 1 mCi, i.v.). The hyperfixation was measured by comparing the inflammatory areas. In the group treated with zinc acexamate, the regression of inflammation was highly significant (p less than 0.001) in comparison with the other groups. These results emphasize the importance of combining zinc with acexamic acid for healing skin wounds.

Anti-ulcer and membrane stabilizing actions of zinc acexamate

The effects of zinc acexamate on stress and reserpine ulcers as well as on gastric mast cells degranulation and membrane stability were evaluated in the rat. Zinc acexamate (100 mg/kg) has demonstrated an inhibitory effect on cold-restraint stress and reserpine-induced ulcer in a dose-dependent manner. Pretreatment of rats, prior to cold restraint stress, reduced gastric mast cell degranulation. Zinc acexamate (10(-4) M) inhibits Triton X-100 release of beta-glucuronidase in isolated hepatic lysosomes. These observations suggest that ulcer protective actions of zinc acexamate may be exerted in part through enhancing gastric mucosal resistance by stabilizing biological membrane integrity.

Effects of EACA on thrombin generation as measured by the chromagen S2238

In the presence of epsilon aminocaproic acid (EACA) thrombin generation in recalcified platelet rich plasma (PRP) was markedly stimulated, as measured by the cleavage of the synthetic substrate S2238. However, thrombin activity remaining after 30 minutes incubation was reduced when compared with control values. The residual activity was shown to be hirudin insensitive and to be associated with a species of higher molecular weight than free thrombin. These results suggested an inhibition of thrombin binding to the antithrombin, alpha 2-macroglobulin (alpha 2M). Preincubation of PRP with EACA reduced the concentration at which EACA elicited its dual effects. Similar results were obtained with the alpha 2M inhibitor, hydrazine. These experiments indicated that alpha 2M may play a more important role in regulating thrombin generation than has been previously recognized.

[Effects of epsilon-aminocaproic acid, amben and kontrikal on fibrinolysis due to tissue-type plasminogen activator from the pig heart]

Simultaneous intravenous administration to rats of epsilon-aminocaproic acid and high doses of plasminogen tissue activator from the pig heart was shown to prevent fibrinolysis changes induced by the tissue activator. Amben completely suppressed the action of the tissue activator at the blood concentration 15 times less than that of epsilon-aminocaproic acid. A greater effect of amben on the blood activator level was noted. Contrykal exerted only slight effect on fibrinolysis stimulated by the tissue activator.

[Effect of synthetic and natural inhibitors on the activity of tissue activator from the swine heart in vitro]

Activity of tissue activator, isolated from pig heart, was studied in vitro in presence of synthetic inhibitors epsilon-aminocapronic acid and amben as well as of natural inhibitor contrical. All the inhibitors studied inhibited the tissue activator as shown by analyses on fibrin plates and by means of quantitative estimation of thrombolytic activity in fibrinolytic preparations in vitro. Among the two synthetic inhibitors amben exhitited the highest effect on the tissue activator: its effect was 3-4-fold higher as compared with epsilon-aminocapronic acid.

The autodigestion of human plasmin follows a bimolecular mode of reaction subject to product inhibition

Plasmin is a labile enzyme destroyed by a process termed autodigestion. Studied by a kinetic assay on the substrate Tos-Gly-Pro-Lys-pNA this process is shown to follow a bimolecular mode of reaction, which is retarded by plasmin degradation products. Plasmin is protected by fibrinogen, by epsilon-aminocaproic acid (6-aminohexanoic acid), by increasing ionic strength, and by glycerol. CNBr fragments of fibrinogen did not protect. Lack of substrate protection of plasmin may give rise to errors in a two-stage plasminogen activator assay, while the presence of substrate in a one-stage method prevents degradation of the generated plasmin.

Studies of angiotensin I converting enzyme: effects of kinins, bacitracin, gamma-aminobutyric and epsilon-aminocaproic acids, and related compounds on substrate binding and catalysis in vitro

Bradykinin and 22 of its analogs were evaluated for their abilities to inhibit the hydrolysis of [3H]hippurylglycylglycine by purified porcine kidney angiotensin I converting enzyme. The mean inhibitory concentration (IC50) for bradykinin was 1.2 +/- 0.2 X 10(-6) M. Except for Ile-Ser-bradykinin and [Sar4]-bradykinin, none of the kinin analogs were more potent in this regard than bradykinin. Bacitracin, gamma-aminobutyric acid, epsilon-aminocaproic acid, and structurally related compounds were also tested. The IC50 value for bacitracin was 1.9 +/- 0.4 X 10(-4) M, gamma-aminobutyric acid, 83.4 +/- 7.2 mM, and for epsilon-aminocaproic acid, 7.0 +/- 1.4 mM. Compounds were also evaluated for their abilities to prevent 125I-labelled [Tyr1]-kallidin binding to angiotensin I converting enzyme inhibited by EDTA. The IC50 values for bradykinin, bacitracin, gamma-aminobutyric acid, and epsilon-aminocaproic acid were 1.6 +/- 0.3 X 10(-8) M, 2.6 +/- 0.9 X 10(-6) M, greater than 291 mM, and 13.2 +/- 3.9 mM, respectively.

Stabilizing effect of epsilon-aminocaproic acid on allergenic extracts

The effect of epsilon-aminocaproic acid (EACA) on the degradation of an aqueous Lolium perenne extract was studied by intracutaneous tests and by RAST inhibition. Extracts for skin testing stored at 4 degrees C for 12 months and at 37 degrees C for 6 weeks were significantly protected from degradation by addition of 0.1 mol/L of EACA before storage. Extracts were stored for RAST inhibition at 4 degrees C for 6 months and at 37 degrees C for 7 days. Shelf life was twofold to threefold increased when 0.1 mol/L of EACA was added to the dilution medium. EACA also protected the extracts from the effect of freezing and thawing. Comparison with the effect of human serum albumin indicated a rather short activity of human serum albumin, whereas the effect of EACA lasted longer. It is suggested that EACA can be used to increase the stability of aqueous allergen extracts for skin testing and for hyposensitization therapy.

Reduced cofactor function of human high molecular weight kininogen induced by rat plasma kallikrein

Plasma kallikrein purified from acetone-activated, plasminogen-free rat plasma yielded in polyacrylamide gel electrophoresis protein bands corresponding to Mr values of 143,000 (main band) and 135,000 (lighter band). After SDS treatment without reduction the protein pattern had changed to two strong bands corresponding to Mr values of 87,000 and 78,000. Gel electrophoresis of kallikrein purified from plasma of rats pretreated with clinical dextran (200 mg/kg intravenously) produced main bands corresponding to Mr values of 120,000-130,000 and 78,000-80,000 for native samples and SDS-treated samples respectively (Johansen & Briseid 1983). Both kinds of kallikrein reduced the capacity of human high molecular weight kininogen to function as a cofactor in the surface-mediated activation of factor XII in a crude plasma preparation. The preparation obtained from plasma of dextran-treated rats was significantly more potent than was the normal kallikrein preparation, both as regards the effect against HMrK, and as an activator of plasminogen.

Assay of human fibrinopeptides by high-performance liquid chromatography

Fibrinopeptides A, AP, and B, desarginine fibrinopeptide B, and a previously unknown peptide corresponding to B beta 3-14 were resolved within 10 min by an HPLC technique using an isocratic solvent system (22% acetonitrile in 0.1% trifluoroacetic acid) and a 0.46 X 10-cm Spherisorb ODS-2 (3-micron) octadecylsilane column. Fibrinopeptides A and AY eluted in the same peptide peak. The method was used to evaluate a carboxypeptidase which converts fibrinopeptide B into its desarginine form. Fifty percent inhibition of this activity occurred at 1.7 mM epsilon-aminocaproic acid (EACA). At saturating substrate concentrations the rates of total fibrinopeptides A and B release were unaffected by 125 mM EACA, a concentration at which the carboxypeptidase activity is completely inhibited.

Clinical application of inhibitors of fibrinolysis

The basic proteinase inhibitor from bovine organs, aprotinin, was first identified in 1930 and its effect on enzyme and other biological systems has since been extensively studied. Aprotinin can only be administered intravenously and has a half-life of about 2 hours. Its administration at the start of cardiopulmonary bypass surgery appears to reduce blood loss and to protect against global myocardial ischaemia. Similarly, a smaller infarct size seems to result from early administration of aprotinin within the first hour after myocardial infarction, though further studies are needed to confirm this effect. A combination of aprotinin with tranexamic acid may be effective in preventing or delaying rebleeding after rupture of an intracerebral aneurysm; the addition of aprotinin seems to decrease the incidence of delayed cerebral vasospasm and ischaemic complications which are sometimes noted when tranexamic acid alone is used. Aprotinin is also effective as adjuvant treatment in traumatic haemorrhagic shock. The recommended loading dose is 15,000 to 20,000 KIU/kg bodyweight administered as a short intravenous infusion, followed by 50,000 KIU/hour by continuous infusion. Side effects of aprotinin are very rare. Epsilon-Aminocaproic acid (EACA), p-aminomethylbenzoic acid (PAMBA) and tranexamic acid are synthetic antifibrinolytic amino acids. Saturation of the lysine binding sites of plasminogen with these inhibitors displaces plasminogen from the fibrin surface. On a molar basis tranexamic acid is at least 7 times more potent that epsilon-aminocaproic acid and twice as potent as p-aminomethylbenzoic acid. All 3 compounds are readily absorbed from the gastrointestinal tract and excreted in active form in the urine. The plasma half-life of tranexamic acid is about 80 minutes. The main indications for tranexamic acid are the prevention of excessive bleeding after tonsillectomy, prostatic surgery, and cervical conisation, and primary and IUD-induced menorrhagia. It is possible that gastric and intestinal bleeding can also be reduced as well as recurrent epistaxis. Tranexamic acid could also be useful after ocular trauma. The value of fibrinolysis inhibitors in the prevention of bleeding after tooth extraction in patients with haemophilia is well documented, as is the treatment of hereditary angioneurotic oedema. The usual dose of tranexamic acid is 0.5 to 1g (10 to 15 mg/kg bodyweight) given intravenously 2 to 3 times daily, or 1 to 1.5 g orally 3 to 4 times daily. This dose needs to be reduced in patients with renal insufficiency. The main side effects of tranexamic acid are nausea or diarrhoea.

Effects of zinc acexamate on gastric mucosal resistance factors

The effects of zinc acexamate on gastric defensive systems were evaluated in the rat. Gastric ulcers induced by oral administration of three necrotic agents (0.6 N HCl, 25% NaCl, 100% ethanol) were markedly reduced by different pretreatments with zinc acexamate. This cytoprotective effect was not modified by previous treatment with indomethacin (30 mg/kg orally). Zinc acexamate pretreatment also prevents the disruption of the gastric mucosal barrier induced by aspirin (40 mM) and increases mucus production in the gastric glands and tracheal walls. These observations suggest that the antiulcer effects described for zinc salts could be the result, at least partly, of an action increasing gastric mucosal defensive systems.

The involvement of collagenolysis in ovulation in the rat

Collagenolytic activity in ovarian follicles was previously demonstrated by using synthetic peptides and reconstituted collagen fibers. However, attempts to demonstrate degradation of ovarian collagen and to correlate collagenase activity with ovulation were not successful. By administration of L-(5-3H) proline, we have labeled ovarian and follicular collagen and followed collagenolytic activity by separation of 3H-hydroxyproline (3H-Hyp) from acid hydrolyzates of ovarian tissue by HPLC. The level of ovarian and follicular 3H-Hyp decreased by about 40% on the afternoon of proestrus or after exogenous stimulation of ovulation by human CG (hCG), and this decrease was abolished by blocking the surge of gonadotropins with Nembutal. To verify that the observed reduction in 3H-Hyp was due to the action of a typical collagenase, the collagenous fraction was prepared from ovarian tissue and from preovulatory follicles before and after the ovulatory stimulus. The extracts were treated with trypsin (25 min, 25 C, 0.01 mg/ml) plasmin and p-amino-phenyl-mercuric acetate to fully activate the collagenase extracted along with collagen. Both, enzymatic and chemical activation of collagenase in vitro resulted in degradation of collagen. This degradation could be inhibited by cysteine and EDTA; both are classic inhibitors of mammalian collagenases. The activity of ovarian collagenase increased within 3 h after hCG-stimulation, peaked at 5-fold 6 h after hCG, and declined afterwards. Administration of cysteine (0.001-0.01 mmol) into the bursal cavity of proestrous rats blocked ovulation and breakdown of ovarian collagen in a dose-dependent manner. Cysteine effectively inhibited ovulation even when injected 7 h after the hCG stimulus. Inhibitors of arachidonic acid metabolism prevent ovulation. Indomethacin (inhibitor of cyclooxygenase) and nordihydroguaiaretic acid (inhibitor of lipoxygenase) blocked ovulation and inhibited hCG-induced ovarian collagenolysis. Collectively, these results corroborate the essential role of collagenolysis in follicular rupture in mammals.

Effect of epsilon-aminocaproic acid on postvitrectomy hemorrhage

We performed a prospective study involving 96 patients undergoing vitrectomy for proliferative diabetic retinopathy to determine the effect of epsilon-aminocaproic acid on the occurrence of postoperative intraocular hemorrhage. epsilon-Aminocaproic acid significantly reduced postoperative vitreous hemorrhage during the immediate postoperative period. Follow-up examinations two to six weeks after discharge from the hospital disclosed no statistically significant difference in the severity of vitreous hemorrhage between the treated and untreated groups. The loss of drug effect at this stage was in part due to spontaneous repeated bleeding in the treated group and in part to spontaneous clearing of hemorrhage in the untreated group. There was no statistically significant difference in the rate of repeated bleeding between the two groups or in rate of spontaneous clearing.

Perfusion outflow facility in the rabbit eye. Stabilization by EACA

The time-dependent increase in apparent facility of outflow (washout effect) that occurs with prolonged perfusion of the eye has imposed limitations on the study of aqueous humor dynamics. The washout effect in postmortem in situ rabbit eyes, undergoing constant pressure perfusion with a saline perfusate, can be attenuated dramatically by adding to the perfusate the serine protease inhibitor and antifibrinolytic agent epsilon-aminocaproic acid (EACA) at a concentration of 3.8 X 10(-3) molar. Washout curves from 13 pairs of rabbit eyes, plotted as outflow facility versus time, were fitted by linear regression, and their washout slopes calculated. The washout slope of all of the 13 eyes perfused with normal saline + EACA was lower in magnitude (less washout) than the paired control eye in the same animal, perfused with a control perfusate of normal saline + leucine. Wilcoxon signed rank test yielded P less than 0.001. This suggests that a significant component of the washout effect may be mediated by fibrinolytic activity, or by some EACA sensitive component of the aqueous drainage pathway, and that addition of EACA to a saline perfusate may be useful for blunting the washout effect in prolonged perfusion studies.

Increased plasma proteinase activity of mice bearing the BCL1 leukemia

Plasma samples from mice bearing the BCL1 leukemia were shown to express elevated levels of neutral proteinase activity when assayed with radioiodinated casein as a substrate. Increased plasma proteinase activity reached levels 3-4-fold higher than controls. The increased levels of activity did not correlate with the degree of hepatosplenomegaly or the number of tumor cells in the blood. The onset of the increase in plasma activity correlated with the onset of the leukemic phase of the disease. These findings with the murine leukemia may be analogous to recent findings of abnormal proteinase activity in plasma from patients with acute leukemia.

Role of plasmin, thrombin, and antithrombin III as etiological factors in delayed cerebral vasospasm

The fibrinolytic enzyme plasmin at 0.25 units/ml produced a contraction of isolated canine basilar arteries that developed slowly and was sustained for at least 2 hours. Plasmin and thrombin (1 unit/ml) acted synergistically to enhance the contractile response. In contrast to plasmin, the marked contraction elicited by thrombin ended within 1 hour, and afterward the artery was completely tachyphylactic to thrombin. Fibrin clot, fibrinopeptides, and fibrin degradation products did not prolong significantly the effect of thrombin or prevent the tachyphylaxis. Plasmin and thrombin may occupy a common membrane receptor because exposing the artery briefly to trypsin (24 micrograms/ml) thereafter abolished the contractile effect of plasmin and thrombin without affecting the action of other agonists. Antithrombin III (1.0 unit/ml) relaxed basilar arteries that were precontracted with plasmin (0.5 unit/ml), thrombin (1.0 unit/ml), serotonin (10(-5) M), uridine triphosphate (10(-4) M), or KCl (8 X 10(-2) M). The results suggest that the vasoconstrictor effect of thrombin might contribute to hemostasis after subarachnoid hemorrhage (SAH) but, because of tachyphylaxis, not to delayed vasospasm. On the other hand, the constrictor action of plasmin might appear late in the course of SAH in association with clot lysis and tissue repair. Last, the level of the vasorelaxant antithrombin III in cerebrospinal fluid could control the appearance and severity of cerebral arterial spasm in SAH.

Metabolism of fibrinogen in children with acute lymphoblastic leukaemia

The metabolism and in vivo kinetics of fibrinogen were studied using homologous 125I-labelled fibrinogen in 21 children with acute lymphoblastic leukaemia (ALL). Ten patients were undergoing induction therapy, 11 children were in complete remission on maintenance therapy. Results in the patients undergoing induction therapy were: plasma fibrinogen levels were normal in all except one patient, the plasma fibrinogen pool was elevated in six cases, seven patients had a shortened fibrinogen half-life and increased fractional catabolic rate for fibrinogen. The absolute catabolic rate for fibrinogen was elevated in six cases. This shortened fibrinogen half-life together with the correcting effect of heparinisation on the fibrinogen turnover indicated that fibrinogen was consumed by chronic disseminated intravascular coagulation. Inhibition of the fibrinolytic system with epsilon-aminocaproic acid in five patients had no influence on the fibrinogen half-life in three of them but resulted in its prolongation in two patients. All except two children in complete remission had normal fibrinogen levels. Six patients had elevated plasma fibrinogen pools and in all of the cases survival and fractional catabolic rate of fibrinogen were normal. The absolute catabolic rate for fibrinogen was normal in eight, elevated in three of the patients. This observation indicates that fibrinogen synthesis remains accelerated in some cases of ALL in complete remission, but the cause of this is not known.

Importance of the interaction between plasminogen and fibrin for plasminogen activation by tissue-type plasminogen activator

The potentiating effect of fibrin monomer on plasminogen activation by tissue-type plasminogen activator is much more important with lys-plasminogen than with mini-plasminogen (which lacks the high affinity lysine-binding site important for binding to fibrin). Furthermore, this potentiating effect is totally abolished when lys-plasminogen is eluted from fibrin by the addition of 1 mM epsilon-amino caproic acid. Binding does however not seem to be the only condition required since it was found that fragment D is a much stronger potentiator of the activation of plasminogen by tissue-type plasminogen activator than fragment E although plasminogen binds to both fragment D and fragment E. Furthermore, fragment E has the same effect on the activation of lys-and mini-plasminogen by tissue-type plasminogen activator. Therefore, it is suggested that binding of plasminogen to fibrin involves a conformational change in the plasminogen molecule, facilitating its activation by tissue-type plasminogen activator.

Vasoactive agents and production of thrombosis during intravascular coagulation 1--comparative effects of norepinephrine in thrombin and adenosine diphosphate (ADP) treated rabbits

Pathogenesis of the microthrombi produced during intravascular coagulation was investigated in rabbits given intravenous infusions of thrombin or adenosine diphosphate (ADP). Thrombin, at a dosage producing a fibrinogen consumption of 70% within 4 h (1 unit/kg/min), failed to produce extrapulmonary microthrombi unless fibrinolysis inhibition (epsilon-aminocaproic acid-EACA) or alpha-adrenergic stimulation (norepinephrine) were provided simultaneously. The mechanism whereby norepinephrine initiated glomerular capillary thrombosis was not related to interference with fibrinolysis nor to potentiation of platelet aggregation and blood coagulation, as indicated by similar consumption of plasminogen and platelets in animals given thrombin alone or combined with norepinephrine, and by the lack of correlation between fibrinogen consumption and the incidence and severity of glomerular thrombosis produced with various dosages (1 to 3 mu/kg/min) of norepinephrine. With norepinephrine, microthrombi were also observed in the adrenals, the spleen and the gastric mucosa. Aspirin prevented the phenomena in the latter two organs, but was inactive or aggravating on thrombogenesis elsewhere. ADP associated with thrombin failed to trigger formation of microthrombi but initiated platelet-rich thrombi in the pulmonary vasculature when associated with norepinephrine. We conclude that unlike thrombin, ADP cannot be held responsible for the microthrombi elicited during experimental intravascular coagulation. Furthermore, the ability of norepinephrine to elicit glomerular thrombosis in thrombin injected rabbits may provide an explanation for requirement of alpha-adrenergic stimulation in the endotoxin-induced generalized Shwartzman reaction.

Modulators of plasma fibronectin response during sepsis

Plasma fibronectin (PFN) depletion has been associated with poor outcome in patients with sepsis or those who have experienced trauma; restoration of normal levels appears beneficial. PFN synthesis is increased after cecal ligation even in malnourished animals with sepsis, implying that stimulation of endogenous PFN synthesis is possible. One hundred rats received either a single therapeutic agent (gelatin, heparin, indomethacin, urokinase, captopril, or endotoxin) or the combination of a cecal ligation and a single agent (cimetidine, methylprednisolone, epsilon-aminocaproic acid (EACA), or transaminomethyl cyclohexane carboxylic acid. PFN levels were measured by enzyme-linked immunosorbent assay at 0, 24, and 48 hours. Only endotoxin alone caused significant PFN elevation at 24 to 48 hours (p less than 0.01); however, its multiplicity of effects precludes localization of regulatory pathways. Methylprednisolone results in an accelerated rise in PFN levels after operation (p less than 0.05), probably through an intracellular augmentation PFN synthesis. EACA attenuates the postoperative response while transaminomethyl cyclohexane carboxylic acid augments the PFN rise. This effect of EACA implies the existence of a proteolytic fragment capable of stimulating PFN synthesis. If a nontoxic factor can be identified, the use of exogenous PFN may be avoided.

The mechanism of hepatoprotection by epsilon aminocaproic acid and putrescine

Hepatic neutral serine proteases (including plasminogen activator) and ornithine decarboxylase (ODC) are induced by the hepatotoxin galactosamine (GALN). We examined the hepatoprotection conferred by epsilon-aminocaproic acid (EACA), a fibrinolytic inhibitor, putrescine (PUTR), the polyamine generated from ornithine by ODC, and alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC. GALN, 450 mg/kg, was administered intraperitoneally to Wistar-Lewis rats (group I). Groups II, III, and IV were also given EACA (80 mg/kg), PUTR (0.3 mmol/kg), or DFMO (0.3 mmol/kg), respectively, 1 hour before and 3, 7, and 12 hours after GALN. Rats were killed 2 hours after an intraperitoneal dose of 3H-thymidine was administered, 30 or 45 hours after GALN. EACA and PUTR were effective protectants against necrosis as judged by enzymes and histologic findings. Neither increased thymidine incorporation above the levels seen with GALN only. DFMO offered no protection even though thymidine incorporation at 45 hours was increased. Both EACA and PUTR, which have similar chemical structures, possessed significant antiprotease activity in vitro, suggesting that they act by inhibiting toxin-induced neutral serine protease activity and not by accelerating regeneration.

Venous ulceration, fibrinogen and fibrinolysis

The effect of long and short-term venous hypertension upon lymph fibrinogen concentrations was studied in an attempt to explain the peri-capillary deposition of fibrin reported in patients with post-phlebitic syndromes. The clearance of radioactive fibrinogen/thrombin clots from the subcutaneous tissues of rats and human volunteers was also studied. Both long- and short-term venous hypertension were found to increase fibrinogen transport across the interstitial space by more than 600%. Not only was there evidence of fibrinolytic activity in the lymph but after long-term venous hypertension alpha 2 antiplasmin activity was also detectable. Skin biopsies from the venous hypertensive ankles showed deposition of interstitial fibrin. The clearance of radioactive fibrinogen/thrombin clots from the subcutaneous tissues of the rat was found to be delayed if the rats were given epsilon amino caproic acid but it could not be increased with stanozolol. In human subjects it was found that patients with lipodermatosclerosis had delayed clot clearance and retarded blood fibrinolytic activity when compared with normal volunteers and patients with uncomplicated varicose veins. The principle cause why tall men are more subject to ulcers than short men, Dr Young conceived to be then length of the column of blood in their veins; which by its pressure, renders the legs less able to recover when hurt by any violence.

A direct, plasmin-independent assay for plasminogen activator

A direct assay for plasminogen activator (PA) was developed. It employed polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and beta-mercaptoethanol to monitor PA-mediated conversion of single chain, 125I-plasminogen to two chain plasmin. By incorporating Triton X-100, albumin and trasylol in the reaction buffer, we were able to minimize the adsorptive and autolytic loss of reactants frequently associated with similar approaches. Under these conditions, plasmin formation was linear for at least 24 hours, dose-dependent over a 20-fold range of urokinase concentrations, and at least 100-fold more sensitive (0.05 units/ml) than previously reported direct assays for PA. The versatility of the assay was demonstrated by its ability to distinguish between urokinase-like and tissue-type PA, and to quantitate the effects of agents like fibrin and epsilon-amino caproic acid on their respective activities. The assay was readily adapted to detect inhibitors of PA in various samples, and was employed to demonstrate the presence of such inhibitors in both rabbit and bovine endothelial cells. Interestingly, the rabbit inhibitor was found to block the activity of urokinase but not that of tissue-type PA, while the bovine inhibitor neutralized the activities of both molecules. These results demonstrate that cleavage of 125I-plasminogen can be employed as a direct, sensitive and quantitative assay for various PAs, and thus offers a new approach for studying plasminogen activation and agents that stimulate or inhibit it.

Fluorescence spectrophotometric studies on the conformational changes induced by omega-aminoacids in two isozymes of Glu-plasminogen (I and II)

Glu-plasminogen I (Glu-plg I: with two carbohydrate chains) and Glu-plg II (with one carbohydrate chain) were separated by a gradient elution of 6 aminohexanoic acid (6AHA) through lysine-Sepharose. Each preparation was excited with ultraviolet light of wave length at 291 nm. The intensity of fluorescence was measured at 340 nm. The intensity of fluorescence increased to a small extent at 0.02 mM of tranexamic acid (t-x) for Glu-plg I and then quickly increased from 0.1 mM of t-x to reach the peak at 0.6 mM. The intensity of fluorescence for Glu-plg II started to increase at 0.2 mM to reach the peak at 0.7 mM. No small increase of fluorescence was observed at less than 0.2 mM of t-x for Glu-plg II. Kdobs of Glu-plg I for t-x and 6AHA were 0.34 mM and 1.35 mM, respectively, whereas Kdobs of Glu-plg II for t-x and 6AHA were 0.46 mM and 3.3 mM, respectively. When Glu-plg I and II were activated by urokinase (UK) and the hydrolysis of S-2251 was measured, the extent of hydrolysis increased in the presence of t-x and 6AHA. The rate of the increase of S-2251 hydrolysis (thus activation rate of Glu-plg I and II with UK) increased in parallel with increase in fluorescence intensity of Glu-plg I and II in the presence of omega-aminoacids. In conclusion, changes in the activation rate with UK and in fluorescence intensity were observed at lower concentrations of omega-aminoacids for Glu-plg I than for Glu-plg II.

Kinetics of epsilon-aminocaproic acid distribution, elimination, and antifibrinolytic effects in normal subjects

The kinetics of epsilon-aminocaproic acid (EACA) distribution and elimination were studied in six normal subjects after a single 10-gm iv dose. Steady-state distribution volume averaged 30.01 or 0.39 l/kg. Mean elimination t 1/2 was 294 min and the elimination clearance was 0.19 l/min. Renal excretion of unchanged EACA accounted for 68% of its elimination and renal EACA clearance averaged 115% of creatinine clearance. EACA antifibrinolytic effect kinetics were also characterized in five of the subjects by the monitoring of clot lysis times in whole blood and platelet-rich plasma. Peak antifibrinolytic effects were observed 15 to 60 min after peak EACA plasma concentrations were attained. A model of maximal fibrinolysis inhibition (Emax) was used to estimate a half-maximal inhibition (IC50) of 63 +/- 19.7 microgram/ml. This agrees with the value of 0.55 mM or 72 microgram/ml that has been reported for the dissociation constant of the EACA-plasminogen complex and is consistent with the proposed biochemical mechanism of EACA action.

Fluorescence polarization and spectropolarimetric studies on the conformational changes induced by omega-aminoacids in two isozymes of Glu-plasminogen (I and II)

Conformational changes of two isozymes of Glu-plasminogen (Glu-plg I and II) induced by omega-aminoacids were studied by using fluorescence polarization and spectropolarimetry. The rotational relaxation times (Pn) of FITC labeled Glu-Plg I and II decreased in the presence of 6 aminohexanoic acid (6AHA) or tranexamic acid (t-x), which may mean increase in Brownian motion of FITC labeled region (possibly N-terminal region) of Glu-plg I and II when 6AHA or t-x binds with lysine binding sites (LBS) of these plasminogens. Glu-plg II seems to have longer rotational relaxation time compared to that of Glu-plg I, which may mean smaller extent of Brownian motion of FITC labeled region of Glu-plg II in comparison to that of Glu-plg I. The far ultraviolet circular dichroism (CD) spectra indicate that there may be some difference in the polypeptide backbone between Glu-plg I and II, possibly more of beta-structure and less of random coil structure in Glu-plg II in comparison to Glu-plg I. The presence of 6AHA or t-x gave rise to larger change of the negative ellipticity at around 208 nm in Glu-plg I in comparison to its change in Glu-plg II, which may mean the larger extent of conformational change of Glu-plg I induced by 6AHA or t-x than that of Glu-plg II.

Morphological aspects of the rat kidney preserved by cold storage. III. Ultrastructural aspects

The ultrastructural changes of the white Wistar rat kidney, preserved by cold storage into two preservation media (Sacks and Plasmagel) are reported. For each medium two groups of kidney were used; for one of them the medium was used without additives and for the other stabilizing additives were added. The results showed the favourable effects of additives on the maintenance of the cellular ultrastructure during preservation, and more important the damages incurred when Plasmagel was used.