Changes of the activity of acid phosphatase and beta-glucuronidase in isolated platelets of whole-body irradiated rats

In the work presented here we paid our attention to studying changes of the activity of two lysosomal enzymes-acid phosphatase and beta-glucuronidase in platelets after whole-body irradiation and application of certain clinically applied antifibrinolytics (Antilysin Spofa and epsilon-aminocaproic acid) on the activity of these enzymes in isolated platelets. From the results it is obvious that the activity of acid phosphatase and beta-glucuronidase increases in platelets of irradiated rats with a maximum on the 11th day after irradiation. In the same time interval after irradiation the most remarkable thrombocytopenia was observed. The application of Antilysin or EACA to intact, non-irradiated rats affects remarkably neither the activity of the followed enzymes nor the count of platelets. A statistically significant thrombocytopenia, in a comparison with controls was found in whole-body irradiated rats who received EACA or Antilysin. The postirradiation increase of the level of acid phosphatase in platelets exerts a similar character in rats who received EACA or Antilysin as in those who were only irradiated with a difference that the increase of the level of this enzyme was essentially lower in all the time intervals of interest. The beta-glucuronidase level in platelets of rats, who received EACA, was essentially unchanged as compared to controls. The application of Antilysin altered remarkably the level of beta-glucuronidase in platelets of whole-body irradiated rats in a comparison with a level of this enzyme in platelets of rats who received no Antilysin. Most remarkable changes were observed in latter time intervals (11th and 15th day) when the beta-glucuronidase level in platelets of rats after the application of Antilysin was remarkably higher than that in solely irradiated rats.

New aspects of naturally occurring proteases in bovine milk

The scientific literature on milk proteases, along with recent findings in the author's laboratory, are summarized and reviewed comprehensively. Emphasis is on detection of proteolytic enzymes and their activity, purification and kinetic characterization of the isolated enzymes, and technological problems associated with proteolytic enzymes in milk and milk products. Two serine proteinases isolated from milk are compared with plasmin of bovine blood serum. Results from these comparisons strongly suggest that milk proteinase I and plasmin are identical. Proteolysis studies with cold stored milk indicate a direct relationship between gamma-casein formation and milk proteinase association with casein micelles.

On the interaction between human plasma kallikrein and C1-esterase inhibitor

The kinetics of the reaction between human plasma kallikrein and C1-esterase inhibitor was studied in a purified system. By monitoring the inhibition reaction for extended periods of time, it was found to proceed in two consecutive steps, a fast reversible second-order binding step followed by a slower, irreversible first-order transition. The rate constants in this reaction model were determined, as well as the dissociation constant of the initial, reversible enzyme-inhibitor complex. Thus, at 37 degrees C the second-order rate constant k1 was found to be 5 X 10(4) M-1 . s-1, the first-order rate constant k2 was 5 X 10(-4) s-1, and the dissociation constant K was 1.5 X 10(-8) M. Heparin (28 U/ml) and 6-aminohexanoic acid (10 mM) had no effect on the k1 of the reaction.

Morphological aspects of the rat kidney preserved by cold storage. II. The juxtaglomerular apparatus

The present paper reports on the changes occurring in the juxtaglomerular apparatus during preservation of the rat kidney by cold storage, using two media: Sacks and Plasmagel, to which a membrane stabilizing "cocktail" was added (hydrocortisone, chlorpromazine, epsilonaminocaproic acid - EACA, propranolol). Evident alterations appeared at 48 hours more accentuated at 72 and 96 hours, and more intense when preserved in Plasmagel. The most affected structure in the juxtaglomerular apparatus was the macula densa, the epithelial cells having a more stable structure.

[The effect of epsilon-aminocaproic acid on the normalization of embolizing fatty matter in the rabbit lung following experimental fractures. A polarized light study]

It has been confirmed that epsilon-aminocaproic acid (EACA), an inhibitor of fibrinolysis, reduced the incidence of fat embolism in the lung of rabbits with experimental bone fractures. Microscopic specimens of lungs, examined under polarized light, demonstrated the reduced amounts of lipoid materials that were prevalently undergraded. The action of the drug is owed to the inhibition of some primary mechanisms, involved in the genesis and diffusion of post-traumatic fat embolism.

Protease-mediated enhancement of lymphocyte-induced angiogenesis in X-ray irradiated mice

Angiogenesis was induced in mice by intradermal injection of semi-syngeneic splenocytes, and after three days the number of newly formed blood vessels at the injection site was counted. When recipients were total-body irradiated with 700 R 2 hours before the lymphocyte injection, the angiogenesis was significantly higher than in non-irradiated mice. The angiogenesis enhancement was of a systemic (not local) character as revealed in experiments with shielding of irradiated animals. This enhancement was not due to X-ray dependent immunosuppression, as shown in experiments with non-irradiated, pharmacologically immunosuppressed mice. Decreased angiogenesis was observed in irradiated mice after treatment with cortisone acetate, aprotinin, and EACA. The results suggest that proteases might be involved in mediating the angiogenesis enhancement after X-irradiation.

Reversal of shortened platelet survival in rats by the antifibrinolytic agent, epsilon aminocaproic acid

Platelet survival in rabbits and rats is shortened by placing indwelling catheters in the aorta; this shortening appears to be at least partly related to the extent of vessel wall injury and platelet interaction with the repeatedly damaged wall. Treatment of rabbit platelets with plasmin and other proteolytic enzymes in vitro shortens their survival when they are returned to the circulation. Because platelets may be exposed to plasmin and other proteolytic enzymes in rabbits and rats with indwelling aortic catheters, we examined the effect of epsilon-aminocaproic acid (EACA) on platelet survival in rats. At a dose of 1 g/kg every 4 h, EACA significantly reduced whole blood fibrinolytic activity and prolonged the shortened platelet survival in rats with indwelling aortic catheters. Mean platelet survival for untreated rats with indwelling aortic catheters was 38.6 +/- 1.9 h, and for rats treated with EACA, 53.8 +/- 3.8 h. Scanning electron microscopy showed that the injured vessel wall of these animals was mainly covered with platelets and fibrin, whereas in control animals that did not receive EACA, the injured surface was mainly covered with platelets and little fibrin was observed. Thus shortened platelet survival during continuous vessel wall injury may result from the local generation of plasmin or the release of proteolytic enzymes at sites where platelets (and possibly leukocytes) interact with the vessel wall.

Epsilon-amino-caproic acid in the treatment of Osler's hereditary angioneurotic edema

This clinical entity described for the first time by Osler in 1888 presented a great therapeutic problem during many decades because of its severity. Landerman and later on Donaldson and Evans established the pathogenic mechanisms of this disease finding a deficiency in the inhibitor of the first activated component of complement, an alpha 2 aminoglycoprotein, to be the mechanism responsible of the same. More concretely, alterations in the plasmin, kinin and kallikrein systems are those that will lead to a change in vascular permeability with resultant tissue alterations. Four cases of hereditary angioneurotic edema are studied in female patients aged between 15 and 50 years and with family history consistent with angioneurotic familiar edema in which there were six cases of death due to edema of the glottis. Once the diagnosis had been made the patients were subjected to treatment with EACA at doses of 2.5 gm every 6 hours. The determinations of complement were similar in the four cases, with marked decreases in C4 and C1 inhibitor with a decrease in total complement in three cases. Regarding secondary effects, vomiting was found only in one cases, which as the dose was reduced did not necessitate termination of treatment. In summary, considering the results obtained in the cases above, we believe that due to its good tolerance and moderate cost, epsilon-amino-caproic acid at the abovementioned dosage is an excellent pharmacological agent in the treatment of Osler's hereditary angioneurotic edema.

Proteolytic activation of influenza WSN virus in cultured cells is performed by homologous plasma enzymes

The effect of chick embryo allantoic fluid, porcine plasma or canine plasma on virus progeny was studied in cultured chicken, porcine and canine cells infected with influenza WSN virus. Cells incubated either without plasma or with heterologous plasma produced virions which had uncleaved haemagglutinin and low infectivity. Cells incubated with homologous plasma produced highly infectious virions with cleaved haemagglutinin. Little increase of progeny virus infectivity was observed in canine cell-porcine plasma and porcine cell-canine plasma host systems. The addition of protease inhibitors to culture containing homologous plasma, in particular epsilon-amino-n-caproic acid (an inhibitor of plasminogen activation), suppressed cleavage of haemagglutinin, and virions which had uncleaved haemagglutinin and low infectivity were produced by the cells. It therefore follows that haemagglutinin cleavage and activation of influenza WSN virus infectivity in cultured cells is most efficiently performed by homologous plasma proteolytic enzyme(s). The mechanism of selective plasma-mediated influenza virus proteolytic activation in homologous cells is discussed.

Prevention of damage in acute spinal cord injury by peptides and pharmacologic agents

Cats were used as models of traumatic spinal cord injury. Each experimental animal received a 500 g-cm force to the exposed dura at the level of thoracic fourth vertebra. Somatosensory evoked potentials (SEPs), carotid arterial blood pressure (BP), and abdominal aorta blood flow in the treated groups were compared with those of the control group. The three treated groups received naloxone (5 mg/kg), TRH (5 mg/kg), and a combination of methyl-prednisolone sodium succinate (MP, 35 mg/kg) and epsilon-aminocaproic acid (EACA, 350 mg/kg). The SEPs which were done only in the naloxone treated group approached "normalcy" 24-26 hours after trauma as compared with the absence of SEPs in traumatized untreated group. In all three groups, the treatment increased the blood flow in abdominal aorta significantly. Morphine sulfate increased substance P (SP) immunoreactivity in the dorsal and ventral gray matter. Naloxone not only reversed this effect, it depleted SP below the saline control level. In order to establish that lipid free radicals are responsible for damage to biological membranes, their effects were also investigated in vitro: 14C-GABA uptake by mouse cortical slices which had decreased by 33% in the presence of superoxide (. O-2) generating system, horseradish peroxidase (HRP), was reduced only by 9% when superoxide dismutase was added to the medium. The latter also protected the nerve endings from damage by (. O-2) as examined by electron microscopy. It is concluded that the agents used in this study produce their ameliorating effects by virtue of their anti-inflammatory, anti-oxidant, and membrane stabilizing properties in addition to their effect on enhancing the regional microcirculation. The release of SP by naloxone may be responsible for the increase in blood flow. The consequences of traumatic injury as depicted in Fig. 1 are discussed at length.

The effects of epsilon aminocaproic acid on contractile properties and catecholamine content of rat carotid arteries

The prevalent use of epsilon aminocaproic acid (EACA) to prevent rebleeding in the preoperative management of ruptured intracranial aneurysms raises the question of a relationship between this drug and cerebral vasospasm. The effects of EACA on the contractile properties of the rat common carotid artery were measured in vitro, and the effects of EACA on the catecholamine content of these arteries were determined qualitatively. When carotid artery segments from rats that had been infused with lactated Ringer's solution alone were incubated in the presence of 1 mM EACA, they exhibited a decrease in contractile activity brought about by the presence of either serotonin or norepinephrine, and an increase in contractile activity when potassium chloride was used. These changes were not witnessed if the arterial segments came from rats that had been infused with lactated Ringer's solution containing EACA. No effect of epsilon aminocaproic acid was found on the median effective dose values for each vasoconstrictor used. Fluorescence histochemistry showed no qualitative changes in the catecholamine content of carotid arteries following EACA treatment.

Effect of EACA, PAMBA, AMCA and AMBOCA on fibrinolysis induced by streptokinase, urokinase and tissue activator

A study is presented in which the inhibiting effects of eACA, PAMBA, AMCA and AMBOCA on fibrinolysis induced by three activators have been compared by a clot lysis method. The order of inhibitory potency was AMBOCA greater than AMCA greater than PAMBA greater than EACA. The activity ratios obtained were found to be influenced by the level of inhibition. At low levels of inhibition the differences between the inhibitory activities are usually more pronounced than at high levels. The degree of inhibition is dependent on the fibrinolytic activator used. The order of sensitivity to the inhibitors was, within the analytical conditions used, found to be: tissue activator greater than streptokinase greater than urokinase. The results are discussed in comparison to the different activity ratios reported by others.

Isolation of three separate anaphylatoxins from complement-activated human serum

Recent methodologies used in preparing anaphylatoxins from complement-activated serum are described. Activation of the alternative pathway generates C3a and C5a; however, activation of the classical pathway is required to generate the anaphylatoxin from C4. This article describes an activation scheme that simultaneously generates all three of the anaphylatoxins (e.g., C3a, C4a and C5a) in human serum and outlines a procedure for isolating each as homogeneous products. Purification of intact anaphylatoxins directly from complement-activated serum takes place only if an exopeptidase in serum, known as carboxypeptidase N (SCPN), is properly inhibited. A new series of mercapto derivatives of arginine analogs are introduced as potent and effective inhibitors of SCPN. These inhibitors permit normal complement activation but prevent degradation of the released activation fragments C3a, C4a or C5a. The SCPN inhibitor previously used was 6-aminohexanoic acid (EACA), but it required a 1 M concentration for effective inhibition, the substituted mercapto-guanido compounds prove to be effective in the mM range.

Measurement of fibrinolytic activity after epsilon-aminocaproic acid administration in rats (Rattus norvegicus)

The antifibrinolytic agent, epsilon-aminocaproic acid was administered to rats via either intraperitoneal injection or intravenous infusion. Time-response and dose-response studies of the resultant plasma levels of fibrinolytic activity were measured by a modification of a standard fibrin plate technique. The modified technique involved the addition of human plasma to rat plasma in a ratio of 10:1 (rat:human). The plasma levels of fibrinolytic activity reflected plasma concentrations of epsilon-aminocaproic acid.

Blood fibrinolytic system in rana tigrina

Fibrinolytic activity as well demonstrable in the blood of Rana tigrina. There occurs prompt lysis of diluted plasma; and the plasma euglobulin fraction shows lysis on both unheated and heated fibrin (human or bovine) plates, implying the presence of plasmin-like enzyme in this fraction. The fibrinolytic activity is remarkably inhibited by the erythrocyte-lysate and is moderately enhanced by leucocytes-thrombocytes. EACA suppresses the lysis of dilute cell-free plasma clots at concentrations of 10(-4) M or more, possibly indicating the presence of plasminogen activator in the plasma. Activation of fibrinolysis by human urokinase and not by streptokinase, shows the probable presence of plasminogen and absence of proactivator.

Proteinase inhibitors suppress the formation of granulation tissue in the carrageenin-induced inflammation in rats

Effect of proteinase inhibitors on the carrageenin-induced inflammation was studied. The formation of granulation tissue was markedly inhibited by a single injection of epsilon-amino-n-caproic acid n-hexyl ester (EACA hexyl ester, 300 mg/kg) into the carrageenin-airpouch immediately after carrageenin injection, whereas repeated injections of the inhibitor starting at 12 hr, 24 hr and 48 hr after carrageenin injection were less effective, slightly effective and ineffective, respectively. A dose-dependent inhibition of both the formation of granulation tissue and the migration of polymorphonuclear leukocytes (PMNs) into the inflammatory locus was found by a single injection of EACA hexyl ester into the carrageenin-airpouch immediately after carrageenin injection. Similarly, a single injection of L-1-tosylamide-2-phenylethyl chloromethyl ketone (TPCK, 50 mg/kg) and N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK, 30 mg/kg) inhibited both the formation of granulation tissue and the migration of PMNs into the inflammatory locus. These results suggest that serine proteinase inhibitors such as EACA hexyl ester, TPCK and TLCK exert their anti-inflammatory actions by interfering with the initial inflammatory reactions including the migration of PMNs into inflammatory locus after carrageenin injection.

Pharmacokinetics of epsilon-aminocaproic acid during peritoneal dialysis

Two patients requiring peritoneal dialysis were treated with epsilon-aminocaproic acid (EACA), an antifibrinolytic agent. Samples of serum and dialysate were assayed for EACA concentrations. Total body clearance, dialysis clearance, EACA half-life, and volume of distribution of EACA were calculated. Total body clearance of EACA was 26 ml/min, which is 25% of the drug clearance in patients with normal renal function. Our results suggest that patients undergoing peritoneal dialysis should receive 25% of the usual recommended dose of EACA. Dialysis clearance accounted for only 58% of total body clearance, suggesting an alternative route of elimination of EACA.

[Comparative effectiveness of epsilon-aminocaproic acid and contrical in preventing complement activation on immune complexes]

Experiments on formation of circulatory immune complexes followed by activation of the complement components were made on sensitized guinea-pigs after intravenous injection of human gamma-globulin as specific antigen. epsilon-Aminocaproic acid did not affect the formation of circulatory immune complexes but significantly inhibited complement activation. Contrykal did not alter the formation of the immune complexes but slightly inhibited activation of the complement components.

Selective inhibition of collagen breakdown by proteinase inhibitors in granulation tissue in rats

A rapid breakdown of collagen was found in granulation tissue induced by carrageenin in rats; the half-life of collagen in both growing and resorbing tissues was about 3.5 days, whereas that in non-resorbing tissue was about 7 days. On the other hand, the half-life of noncollagen protein in the growing, resorbing and non-resorbing tissues was about 2-3 days. epsilon-Amino-n-caproic acid n-hexyl ester, an inhibitor of plasmin and trypsin, selectively inhibited collagen breakdown in vivo without affecting the degradation of noncollagen protein or the syntheses of collagen and noncollagen protein in granulation tissues. A similar selective inhibition of collagen breakdown was also found upon treatment with soybean trypsin inhibitor. Collagenase activity was assayed directly in the insoluble 6,000 X g pellet of granulation tissue homogenates. epsilon-Amino-n-caproic acid n-hexyl ester and soybean trypsin inhibitor markedly inhibited the collagen breakdown in granulation tissue pellets in vitro. The results are consistent with those from in vivo experiments and suggest that both the inhibitors indirectly inhibit the collagen breakdown in granulation tissue through the inhibition of a latent collagenase-activating proteinase(s), because none of the inhibitors directly inhibit collagenase. It may be argued, therefore, that a proteinase(s) which activates a latent collagenase plays an important role in the rapid breakdown of collagen in granulation tissues.

The in vitro activation of complement by radiologic contrast materials and its inhibition with epsilon-aminocaproic acid

Radiologic contrast materials activate complement by both the classical and alternative pathways. This activation is time, dose, and temperature dependent and is able to proceed with equal facility in either the presence or absence of Ca++ or Mg++ chelating reagents (EGTA, EDTA). All the components examined (C1, C4, C2, Factor B, C3, and C5) were consumed during complement activation. Immune complexes are produced during interaction of serum with contrast materials. The activation of complement by contrast materials appears to be principally initiated by the activation of plasminogen to plasmin. Inhibition of plasminogen activators by epsilon-aminocaproic acid affects complement activation markedly.

Influence of omega-aminoacids on the activation of the first component of complement at low ionic strength

Cl, is the first component of human complement, was activated to Cls by diluting human plasma in a solution of low ionic strength. The addition of lysine and its related aminoacids to plasma resulted in inhibition of Cl activation, alpha, omega-diaminoacids such as lysine and ornithine were most effective and omega-aminoacids such as 6 aminohexanoic acid were far less effective. Tranexamic acid which is most potent in inhibition of fibrinolysis among those aminoacids was least effective in the inhibition of Cl activation. omega-aminoacids or their analogues hardly inhibited Cls which had already been activated.

Epsilon aminocaproic acid in hemophiliacs undergoing dental extractions: a concise review

On the basis of our review of the literature, it can be concluded that the advantages of E-A.C.A. include (1) safe execution of oral surgical procedures in persons with hemophilia of varying degrees of severity, (2) decrease or total elimination of the need for specific factor replacement therapy, (3) extremely positive cost effectiveness, and (4) reproducibility of results at different hemophilia centers.

A comparison of the effects of intravenous serotonin and dextran on the levels of factor XII, prekallikrein and plasminogen in rat plasma

It was previously observed that serotonin injected intravenously into the rat caused significant reductions in the prekallikrein activator (PKA) and the benzoyl arginine ethyl ester (BAEe)-esterase activities induced in rat plasma by acetone/kaolin activation. In the present work it was demonstrated that serotonin was unable to exert these effects in vitro, in plasma or in whole blood. The assay of PKA and Baee-esterase activities after gel filtration on Sephadex G-100 of acetone-activated plasma from rats treated with serotonin 0.10 mg/kg revealed reduced fragmentation of factor XII, and reduced levels of kallikrein and of an additional BAEe-esterase. Serotonin also lowered the plasminogen level. The serotonin-induced reductions of PKA and BAEe-esterase were inhibited by pretreatment of the rats with epsilon-aminocaproic acid. Evidence was provided that serotonin did not lower the plasma level of factor XII of the coagulation system, but the level of a factor of significance for the activation of factor XII. All the above-mentioned serotonin effects were fundamentally similar to the corresponding effects caused by dextran. It is concluded that the effects of dextran on the plasma parameters mentioned are mediated by the release of endogenous serotonin.

Thrombus weight as a measure of hypercoagulability induced by drugs

Thrombus weight was used as a measure of the thrombus enhancing effect of drugs in 135 rats. The weight of thrombus formed in one hour, on a 20 x 0.5 mm platinum wire, inserted in the vena cava was taken as a measure of thrombosis. The change in thrombus weight which followed the injection of ellagic acid to activate the coagulation system, adenosine diphosphate to activate the platelets, and epsilon-aminocaproic acid to inhibit the fibrinolytic system, was measured. Pilot studies showed that the drug doses used brought about the appropriate changes in the factors named. The mean thrombus weight in 45 control animals was 1.93 mg. Ellagic acid increased it about five-fold, and epsilon-aminocaproic acid almost two-fold, while adenosine diphosphate reduced it by almost a half. Concurrent controls were used in each case. Clotting tests (whole blood clotting time, kaolin-activated whole blood clotting time, thrombin time, and partial thromboplastin time), performed at the end of the hour, showed no significant correlation with thrombus weight.

Biting activity by Aedes egypti mosquitoes in guinea-pigs. An experimental model for screening the effect of some systemically administered compounds

The Aedes egypti mosquito fed consistently on guinea-pigs in a 2-hour period (n = 61), the mean percent feeding rate (+/- S.D.) being 88.84 +/- 9.32. Of a total of 34 different compounds systematally administered in guinea-pigs and tested for their effect on the mosquito biting rate using the above model, five: heparin, sodium fluoride, aminocaproic acid, thiourea and dithiocarb partially reduced the biting rate. The results are consistent with the view that certain aminoacids or proteins of blood or tissues serve as 'pheromones' attracting the mosquito to guinea-pigs.

Separation of plasminogen activators from human plasma and a comparison with activators from human uterine tissue and urine

Normal human plasma contains acid-stable as well as labile plasminogen activators. The activity of activators in plasma euglobulins was inhibited by EACA in an uniform pattern, similar to that obtained with the major activators in human uterine tissue or with the purified porcine tissue activator, but different from the patterns obtained with plasmin or with urokinase. Gel filtration at high ionic strength separated activators corresponding to particle sizes of 60,000 dalton and about 10,000 dalton, corresponding to two activators similarly obtained from human tissue. The 60,000 dalton activator was precipitated in the euglobulin fraction. Its concentration increased in plasma after exercise. The 10,000 dalton activator was found mainly in the supernatant. Gel filtration in 0.15 M solutions yielded activators in fractions of molecular sizes of 100-140,000 dalton and 200,000 dalton or larger. The activity of normal and exercise euglobulins was inhibited by antiserum to a plasminogen activator prepared from porcine tissue, but it was not inhibited by antiserum to urokinase. Plasminogen activators in human plasma euglobulins resembled immunochemically the activators in human uterine tissue.

Separation of plasminogen activators from human uterine tissue and a comparison with activators from human urine and porcine tissue

Three types of plasminogen activator could be distinguished in extracts from human uterine tissue. The activators differed in thermostability or in mode of inhibition by EACA. All the extracts contained stable as well as labile activators. The saline extracts were uniformly inhibited by increasing concentrations of EACA. Extracts made with 2 M ammonium thiocyanate were either uniformly inhibited by EACA or showed deflections indicating contamination with an activator, which was inhibited in a biphasic manner. It was possible to distinguish between: (1) An activator, abundantly present in the tissue, which was uniformly inhibited and stable. (2) Another uniformly inhibited activator, which was labile. (3) An activator, inhibited in a biphasic manner, similar to urokinase, which was present in varying amounts in uteri with the endometrium in the proliferative phase. Gel filtration of the uterine extracts showed two major activity peaks corresponding to particle sizes of 60,000 dalton and about 10,000 dalton. Antiserum to purified plasminogen activator, prepared from porcine ovaries, inhibited the activity of the human uterine extracts, but not the activities of human urokinase or urine. Urokinase antiserum in a concentration completely inhibiting human urine or urokinase, inhibited only 10% or less of the activities of human uterine extracts.

The effect of homologous thrombin and fibrinogen degradation products on fibrinogen synthesis in rabbits

The effect of intravenous infusions of purified homologous FDP and thrombin on fibrinogen synthesis was evaluated in rabbits. De novo fibrinogen production was measured by the rate of incorporation of 75SeM into circulating fibrinogen. After receiving either 100 or 200 NIH U/kg purified homologous thrombin over 1 hr, rabbits demonstrated threefold and fivefold increases in fibrinogen synthesis, respectively. A correlation between the titers of FDP-fdp and the degree of fibrinogen synthesis was evident. Prior administration of epsilon-ACA prevented the accelerated synthesis of fibrinogen induced by thrombin and inhibited the appearance of FDP-fdp in serum. epsilon-ACA did not interfere with normal fibrinogen production. Fibrinogen synthesis was assessed following infusions of FDP prepared by vitro by digestion of rabbit fibrinogen with plasmin and subsequently identified on SDS-polyacrylamide gels. Preparations which contained predominantly stage 2 intermediate (X, Y, D, and E) or stage 3 final (D and E) fragments accelerated fibrinogen synthesis, whereas those containing predominantly stage 1 fragment X did not. Prior treatment with epsilon-ACA did not alter these results. Infusion of the supernatants derived from immunoprecipitation of the FDP by either anti-rabbit fibrinogen antibody or specific anti-human D and E antibodies significantly diminished the enhanced fibrinogen synthesis induced by the unadsorbed materials. These experiments suggest that the accelerated fibrinogen synthesis induced by thrombin is mediated by FDP, with fragments D and E appearing to be the most potent.

Studies on the preservation of red blood cells. Attachment of the third component of human complement to erythrocytes during storage at 4 degrees C

Utilizing an automated antiglobulin test, we have investigated the presence of the third and fourth components of human complement on normal red blood cells (RBCs). Only negligible amounts of the fourth component, C4, could be detected on either freshly collected or stored RBCs. The fragment C3d of the third component, C3, was detectable on both freshly collected and stored normal RBCs. A product derived from C3 and reacting with anti-C3c antibody was only barely detectable on freshly collected normal RBCs. During storage of blood at 4 degrees C, increasing quantities of this material were detected on the RBC membrane. Bromelin treatment rendered stored RBCs completely nonreactive with anit-C3c antibody, whereas only partial loss of reactivity was observed following incubation with heated plasma. In contrast, incubation of EC43 with heated plasma completely abolished their ability to react with anti-C3c antibody. We suggest that the presence of this C3 fragment on stored RBCs may contribute to the development of "preservation injury".