RESUMEN
Snakebite accidents are a public health problem that affects the whole world, causing thousands of deaths and amputations each year. In Brazil, snakebite envenomations are caused mostly by snakes from the Bothrops genus. The local symptoms are characterized by pain, swelling, ecchymosis, and hemorrhages. Systemic disturbances can lead to necrosis and amputations. The present treatment consists of intravenous administration of bothropic antivenom, which is capable of reversing most of the systemic symptoms, while presenting limitations to treat the local effects, such as hemorrhage and to neutralize the snake venom serine protease (SVSP). In this context, we aimed to evaluate the activity of selective serine protease inhibitors (pepC and pepB) in combination with the bothropic antivenom in vivo. Further, we assessed their possible synergistic effect in the treatment of coagulopathy and hemorrhage induced by Bothrops jararaca venom. For this, we evaluated the in vivo activity in mouse models of local hemorrhage and a series of in vitro hemostasis assays. Our results showed that pepC and pepB, when combinated with the antivenom, increase its protective activity in vivo and decrease the hemostatic disturbances in vitro with high selectivity, possibly by inhibiting botropic proteases. These data suggest that the addition of serine protease inhibitor to the antivenom can improve its overall potential.
Asunto(s)
Bothrops , Venenos de Crotálidos , Animales , Antivenenos/farmacología , Antivenenos/uso terapéutico , Brasil , Venenos de Crotálidos/toxicidad , Hemorragia/inducido químicamente , Hemorragia/tratamiento farmacológico , Ratones , Inhibidores de Serina Proteinasa/farmacología , Inhibidores de Serina Proteinasa/uso terapéuticoRESUMEN
The hepatocyte growth factor (HGF)/c-met pathway, which mainly consists of HGF activator (HGFA) and its substrate HGF, protects various types of cells via anti-apoptotic and anti-inflammatory signals. Thrombin is the main physiological activator of such plasmatic pathway, and increased plasma concentrations of HGF have been considered as a molecular marker for some pathological conditions, such as disseminated intravascular coagulation. Since thrombin generation is often linked to tissue injury, and these events are common during snake venom-induced consumption coagulopathies (VICC), our goals were to examine whether Bothrops jararaca venom (Bjv), which induces VICC in vivo: (i) activates the HGF/c-met pathway in vivo and (ii) cleaves zymogen forms of HGFA and HGF (proHGFA and proHGF, respectively) in vitro. Two experimental groups (nâ¯=â¯6, each) of male adult Wistar rats were subcutaneously injected with 500⯵L of 0.9% NaCl solution (control) or sub-lethal doses (1.6â¯mg/kg) of Bjv. Three hours after envenomation, whole blood samples were collected from the carotid arteries to evaluate relevant coagulation parameters using rotational thromboelastometry and fibrinogen level (colorimetric assay). Additionally, the plasma concentration of HGF was assayed (ELISA). Thromboelastometric assays showed that blood clotting and fibrin polymerization were severely impaired 3â¯h after Bjv injection. Total plasma HGF concentrations were almost 6-fold higher in the Bjv-injected group (410.0⯱â¯91) compared with control values (68⯱â¯18â¯pg/mL, pâ¯<â¯0.05). Western blotting assay showed that Bjv processed proHGFA and proHGF, generating bands resembling those generated by thrombin and kallikrein, respectively. In contrast to the serine protease inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF), the metalloprotease inhibitor ethylenediaminetetraacetic acid disodium salt (Na2-EDTA) strongly reduced the ability of Bjv to process proHGFA and generated one active band similar to that of thrombin. Since Bjv contains prothrombin and factor X activators, increased intravascular thrombin formation might partly explain the increased HGF levels after bothropic envenomation. In conclusion, these findings suggest that snake venom metalloproteases may be determinant for elevation of plasma levels of HGF in rats experimentally envenomated with Bjv.
Asunto(s)
Bothrops , Venenos de Crotálidos/toxicidad , Factor de Crecimiento de Hepatocito/sangre , Metaloproteasas/metabolismo , Precursores de Proteínas/sangre , Animales , Coagulación Sanguínea , Venenos de Crotálidos/enzimología , Femenino , Fibrina/análisis , Factor de Crecimiento de Hepatocito/metabolismo , Masculino , Precursores de Proteínas/metabolismo , Ratas Wistar , Serina Endopeptidasas/metabolismo , Inhibidores de Serina Proteinasa/farmacología , Sulfonas/farmacologíaRESUMEN
The assessment of the capacity of antivenoms to neutralize the lethal activity of snake venoms still relies on traditional rodent in vivo lethality assay. ED50 and LD50 assays require large quantities of venoms and antivenoms, and besides leading to animal suffering. Therefore, in vitro tests should be introduced for assessing antivenom neutralizing capacity in intermediary steps of antivenom production. This task is facilitated when one key lethal toxin is identified. A good example is crotoxin, a ß-neurotoxin phospholipase A2-like toxin that presents anticoagulant activity in vitro and is responsible for the lethality of venoms of Crotalus durissus snakes. By using rotational thromboelastometry, we reported recently one sensitive coagulation assay for assessing relative potency of the anti-bothropic serum in neutralizing procoagulant activity of Bothrops jararaca venom upon recalcified factor-XII-deficient chicken plasma samples (CPS). In this study, we stablished conditions for determining relative potency of four batches of the anti-crotalic serum (ACS) (antagonist) in inactivating crotoxin anticoagulant activity in CPS (target) simultaneously treated with one classical activator of coagulation (agonists). The correlation coefficient (r) between values related the ACS potency in inactivating both in vitro crotoxin anticoagulant activity and the in vivo lethality of whole venom (ED50) was 0.94 (p valueâ¯<â¯0.05). In conclusion, slowness in spontaneous thrombin/fibrin generation even after recalcification elicit time lapse sufficient for elaboration of one dose-response curve to pro- or anti-coagulant agonists in CPS. We propose this methodology as an alternative and sensitive assay for assessing antivenom neutralizing ability in plasma of immunized horses as well as for in-process quality control.
Asunto(s)
Antivenenos/farmacología , Venenos de Crotálidos/toxicidad , Crotalus , Crotoxina/toxicidad , Tromboelastografía/métodos , Animales , Coagulación Sanguínea/efectos de los fármacos , Pollos , Venenos de Crotálidos/inmunología , Caballos , Pruebas de NeutralizaciónRESUMEN
The assessment of the capacity of antivenoms to neutralize the lethal activity of snake venoms still relies largely on traditional rodent lethality assay (LD50). However, adequately validated in vitro tests should be introduced for assessing antivenom neutralizing capacity in plasma of immunized horses as well as for in-process quality control. The dynamic of fibrin formation in recalcified avian plasma samples is extremely slow, when compared to that presented by mammalian plasmas. In this study, we present one new coagulant assay, by performing dose-response curve after plotting the clotting time (CT) parameter of the ROTEM profile of recalcified chicken plasma samples (target) against semi-logarithmic doses of Bothrops jararaca venom (agonist), either in absence or in presence of the semi-logarithmic doses of anti-bothropic serum (ABS) (antagonist). The mean coagulant dose 50% (CD50) was defined as the quantity of venom (in µg) which reduces CT to 900 s, between minimum and maximum responses. The CT induced by 5CD50 of the venom was used as the control for calculating the effective dose (ED) of each batch of ABS. ED was defined as the ABS dose (nanoliters, nL) at which CT induced by one amount of venom corresponding to 5CD50 is displaced to the maximum threshold (1800 s). Five batches of the ABS, previously assayed for their lethality neutralizing activity (ED50) were assayed. The correlation coefficient (r) between both in vitro (ED) and in vivo (ED50) values was 0.87 (p value < 0.05). We propose this micro method as highly sensitive for characterization and quantification of possible procoagulant activity of small doses of snake venoms (nanograms) and for detecting small doses (nanoliters) of specific antibodies against this effect in little volume samples of biological fluids.
Asunto(s)
Antivenenos/farmacología , Coagulantes/toxicidad , Venenos de Crotálidos/toxicidad , Animales , Bothrops , Pollos , Femenino , Masculino , Tiempo de ProtrombinaRESUMEN
Incubation of plasma from the snake Crotalus durissus terrificus (CDTP) with trypsin generated two hypotensive peptides. The primary structure of the peptides was established for two sequences as: (Ser-Ile-Pro-Gln-Ala-Pro-Thr-Ser-Asn-Leu-Ile-Glu-Ala-Thr-Lys) and (Lys-Pro-Asp-Ala-Asn-Gln-Val-Leu-Ile-Gln-Val-Ile-Gly-Val). These peptides display homology with fragments of albumin from Trimeresurus flavoviridis. Bolus intra-arterial injection of the purified or the synthetic peptide produced a strong and sustained vasopressor response in the anaesthetized snake (CDT) and rats (Wistar); this hypotensive effect was also potentiated by captopril-an angiotensin-converting (0.1 mg/kg) enzyme inhibitor.
Asunto(s)
Antihipertensivos/farmacología , Crotalus , Péptidos/farmacología , Vasoconstrictores/farmacología , Secuencia de Aminoácidos , Animales , Antihipertensivos/química , Antihipertensivos/aislamiento & purificación , Captopril/farmacología , Sinergismo Farmacológico , Femenino , Inyecciones Intraarteriales , Masculino , Datos de Secuencia Molecular , Péptidos/química , Péptidos/aislamiento & purificación , Ratas , Ratas Wistar , Vasoconstrictores/aislamiento & purificaciónRESUMEN
The generation of bradykinin (BK; Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) in blood and kallidin (Lys-BK) in tissues by the action of the kallikrein-kinin system has received little attention in non-mammalian vertebrates. In mammals, kallidin can be generated by the coronary endothelium and myocytes in response to ischemia, mediating cardioprotective events. The plasma of birds lacks two key components of the kallikrein-kinin system: the low molecular weight kininogen and a prekallikrein activator analogous to mammalian factor XII, but treatment with bovine plasma kallikrein generates ornitho-kinin [Thr6,Leu8]-BK. The possible cardioprotective effect of ornitho-kinin infusion was investigated in an anesthetized, open-chest chicken model of acute coronary occlusion. A branch of the left main coronary artery was reversibly ligated to produce ischemia followed by reperfusion, after which the degree of myocardial necrosis (infarct size as a percent of area at risk) was assessed by tetrazolium staining. The iv injection of a low dose of ornitho-kinin (4 microg/kg) reduced mean arterial pressure from 88 +/- 12 to 42 +/- 7 mmHg and increased heart rate from 335 +/- 38 to 402 +/- 45 bpm (N = 5). The size of the infarct was reduced by pretreatment with ornitho-kinin (500 microg/kg infused over a period of 5 min) from 35 +/- 3 to 10 +/- 2% of the area at risk. These results suggest that the physiological role of the kallikrein-kinin system is preserved in this animal model in spite of the absence of two key components, i.e., low molecular weight kininogen and factor XII.
Asunto(s)
Bradiquinina/análogos & derivados , Cardiotónicos/uso terapéutico , Cininas/efectos de los fármacos , Infarto del Miocardio/prevención & control , Vasodilatadores/uso terapéutico , Enfermedad Aguda , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Bradiquinina/uso terapéutico , Captopril/farmacología , Pollos , Modelos Animales de Enfermedad , Precondicionamiento Isquémico Miocárdico , Cininas/sangre , Cininas/fisiología , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Cuidados Preoperatorios , Resistencia Vascular/efectos de los fármacosRESUMEN
The generation of bradykinin (BK; Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) in blood and kallidin (Lys-BK) in tissues by the action of the kallikrein-kinin system has received little attention in non-mammalian vertebrates. In mammals, kallidin can be generated by the coronary endothelium and myocytes in response to ischemia, mediating cardioprotective events. The plasma of birds lacks two key components of the kallikrein-kinin system: the low molecular weight kininogen and a prekallikrein activator analogous to mammalian factor XII, but treatment with bovine plasma kallikrein generates ornitho-kinin [Thr6,Leu8]-BK. The possible cardioprotective effect of ornitho-kinin infusion was investigated in an anesthetized, open-chest chicken model of acute coronary occlusion. A branch of the left main coronary artery was reversibly ligated to produce ischemia followed by reperfusion, after which the degree of myocardial necrosis (infarct size as a percent of area at risk) was assessed by tetrazolium staining. The iv injection of a low dose of ornitho-kinin (4 µg/kg) reduced mean arterial pressure from 88 ± 12 to 42 ± 7 mmHg and increased heart rate from 335 ± 38 to 402 ± 45 bpm (N = 5). The size of the infarct was reduced by pretreatment with ornitho-kinin (500 µg/kg infused over a period of 5 min) from 35 ± 3 to 10 ± 2 percent of the area at risk. These results suggest that the physiological role of the kallikrein-kinin system is preserved in this animal model in spite of the absence of two key components, i.e., low molecular weight kininogen and factor XII.
Asunto(s)
Animales , Bradiquinina/análogos & derivados , Cardiotónicos/uso terapéutico , Cininas/efectos de los fármacos , Infarto del Miocardio/prevención & control , Vasodilatadores/uso terapéutico , Enfermedad Aguda , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Presión Sanguínea/efectos de los fármacos , Bradiquinina/uso terapéutico , Pollos , Captopril/farmacología , Modelos Animales de Enfermedad , Precondicionamiento Isquémico Miocárdico , Cininas/sangre , Cininas/fisiología , Infarto del Miocardio/metabolismo , Infarto del Miocardio/patología , Cuidados Preoperatorios , Resistencia Vascular/efectos de los fármacosRESUMEN
Incubation of plasma from the snake Bothrops jararaca (BJP) with trypsin generated two hypotensive peptides. The primary structure of the peptides was established for three sequences as: Asn-Pro-Phe-Val-Asp-Ala (fraction 13), Ser-Lys-Pro-Asn-Met-Ser-Asp-Glu-Ser-Leu-Ala-Val-Ala-Ile (fraction 14), Asn-Pro-Phe- Val-Asp-Ala (fraction 15). These peptides display homology with fragments of albumin from Trimeresurus flavoviridis. A bolus intra-arterial injection of the purified or the synthetic peptide produced a strong and sustained vasopressor response in the anaesthetized snake B. jararaca and Wistar rats; this hypotensive effect was also potentiated by captopril, an angiotensin-converting enzyme inhibitor (0.1 mg/kg). The natural concentrations of these peptides in plasma need to be determined and could play a physiological role in snake blood pressure regulation.
Asunto(s)
Antihipertensivos/farmacología , Oligopéptidos/farmacología , Péptidos/farmacología , Secuencia de Aminoácidos , Animales , Presión Sanguínea/efectos de los fármacos , Bothrops , Bradiquinina/metabolismo , Cromatografía Líquida de Alta Presión , Sinergismo Farmacológico , Femenino , Hipotensión/inducido químicamente , Masculino , Oligopéptidos/sangre , Oligopéptidos/aislamiento & purificación , Péptidos/sangre , Péptidos/aislamiento & purificación , Ratas , Ratas WistarRESUMEN
BACKGROUND: The hemostatic system is the major target of snake venom serine proteinases (SVSPs) that act on substrates of the coagulation, fibrinolytic and kallikrein-kinin systems. Bothrops protease A (BPA), the most glycosylated SVSP, is a non-coagulant, thermostable enzyme. A cDNA encoding BPA showed that the protein has a calculated molecular mass of 25 409 Da, implying that approximately 62% of its molecular mass as assessed by sodium dodecylsulfate polyacrylamide gel electrophoresis (67 kDa) is due to carbohydrate moieties. RESULTS: Here we show that BPA is a potent fibrinogenolytic agent in vitro, as it readily degraded human and rat fibrinogen at a very low enzyme concentration. Partially N-deglycosylated BPA (p-N-d-BPA) generated similar fibrinogen products, but with enhanced fibrinogenolytic activity. In vivo, injection of 0.75 nmoles of BPA in rats completely avoided thrombus formation induced by stasis in the vena cava, or by endothelium injury in the jugular vein. Moreover, it decreased the fibrinogen plasma level and prolonged the recalcification time. Cleavage of fibrinogen in human and rat plasma was observed with native BPA and p-N-d-BPA by electrophoresis followed by western blot using an anti-fibrinogen antibody. BPA did not cause unspecific degradation of plasma proteins and did not cleave isolated albumin, vitronectin and fibronectin at the same concentration used with fibrinogen. Serine proteinase inhibitors failed to inhibit BPA, probably due to steric hindrance caused by its huge carbohydrate moieties. CONCLUSIONS: To the best of our knowledge, this investigation underscores a new, thermostable, specific defibrinogenating agent that may have an application in the prevention of thrombus formation.
Asunto(s)
Fibrinolíticos/farmacología , Serina Endopeptidasas/metabolismo , Serina Endopeptidasas/farmacología , Venenos de Serpiente/enzimología , Venenos de Serpiente/farmacología , Animales , Fibrinógeno/metabolismo , Fibrinolíticos/química , Glicosilación , Humanos , Técnicas In Vitro , Masculino , Ratas , Ratas Wistar , Serina Endopeptidasas/química , Inhibidores de Serina Proteinasa/farmacología , Venenos de Serpiente/química , Especificidad por Sustrato , Trombosis/prevención & controlRESUMEN
The venom of Lonomia obliqua caterpillar may induce a hemorrhagic syndrome in humans, and blood incoagulability by afibrinogenemia when intravenously injected in laboratory animals. The possible antithrombotic and thrombolytic activities of L. obliqua caterpillar bristle extract (LOCBE) were evaluated in this study. The minimal intravenous dose of the extract necessary to induce afibrinogenemia and anticoagulation was 3.0 and 10.0 microg protein/kg body weight for rabbits and rats, respectively. In rabbits, this dose induced total blood incoagulability for at least 10 h and did not reduce the weight of preformed venous thrombi, in contrast to streptokinase (30,000 IU/kg). In rats, pretreatment with 5.0 and 10.0 microg/kg LOCBE prevented the formation of thrombi induced by venous stasis or by injury to the venous endothelium. The dose of 5.0 microg/kg LOCBE did not modify blood coagulation assay parameters but increased bleeding time and decreased plasma factor XIII concentration. When the extract was administered to rats at the dose of 10.0 microg/kg, the blood was totally incoagulable for 6 h. These data show that LOCBE was effective in preventing experimental venous thrombosis in rats, justifying further studies using purified fractions of the extract to clarify the mechanisms of this effect.
Asunto(s)
Anticoagulantes/farmacología , Venenos de Artrópodos/farmacología , Coagulación Sanguínea/efectos de los fármacos , Fibrinolíticos/farmacología , Trombosis de la Vena/prevención & control , Animales , Anticoagulantes/uso terapéutico , Venenos de Artrópodos/uso terapéutico , Tiempo de Sangría , Factor XIII/análisis , Fibrinolíticos/uso terapéutico , Venas Yugulares/efectos de los fármacos , Masculino , Conejos , Ratas , Ratas Wistar , Venas Cavas/efectos de los fármacosRESUMEN
The venom of Lonomia obliqua caterpillar may induce a hemorrhagic syndrome in humans, and blood incoagulability by afibrinogenemia when intravenously injected in laboratory animals. The possible antithrombotic and thrombolytic activities of L. obliqua caterpillar bristle extract (LOCBE) were evaluated in this study. The minimal intravenous dose of the extract necessary to induce afibrinogenemia and anticoagulation was 3.0 and 10.0 æg protein/kg body weight for rabbits and rats, respectively. In rabbits, this dose induced total blood incoagulability for at least 10 h and did not reduce the weight of preformed venous thrombi, in contrast to streptokinase (30,000 IU/kg). In rats, pretreatment with 5.0 and 10.0 æg/kg LOCBE prevented the formation of thrombi induced by venous stasis or by injury to the venous endothelium. The dose of 5.0 æg/kg LOCBE did not modify blood coagulation assay parameters but increased bleeding time and decreased plasma factor XIII concentration. When the extract was administered to rats at the dose of 10.0 æg/kg, the blood was totally incoagulable for 6 h. These data show that LOCBE was effective in preventing experimental venous thrombosis in rats, justifying further studies using purified fractions of the extract to clarify the mechanisms of this effect
Asunto(s)
Animales , Ratas , Conejos , Masculino , Anticoagulantes , Venenos de Artrópodos , Coagulación Sanguínea , Fibrinolíticos , Trombosis de la Vena , Anticoagulantes , Venenos de Artrópodos , Tiempo de Sangría , Factor XIII , Fibrinolíticos , Venas Yugulares , Ratas Wistar , Venas CavasRESUMEN
Several bradykinin potentiators were identified in the venom of Bothrops jararacussu by chromatographic techniques and biological assays. One of them which was isolated inhibited the angiotensin-converting enzyme in vitro and potentiated the bradykinin-induced lowering of the arterial pressure in the rat.
Asunto(s)
Bradiquinina/farmacología , Venenos de Crotálidos/farmacología , Músculo Liso/efectos de los fármacos , Oligopéptidos/farmacología , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Captopril/farmacología , Cromatografía en Gel , Cromatografía Líquida de Alta Presión , Venenos de Crotálidos/química , Sinergismo Farmacológico , Femenino , Cobayas , Íleon , Masculino , Contracción Muscular/efectos de los fármacos , Oligopéptidos/química , Oligopéptidos/aislamiento & purificación , Técnicas de Cultivo de Órganos , Ratas , SerpientesRESUMEN
The venom of the Brazilian snake Bothrops jararacussu, was found to contain peptides capable of potentiating the smooth muscle contracting activity of bradykinin (BK). Chromatographic separation on Sephadex G-25 and Sephadex G-10 respectively, yielded an active peptide which at a concentration of 0.6 micrograms/ml doubled the effect of a single dose of BK on the isolated guinea-pig ileum. HPLC chromatography showed this material to contain one major and 4 minor components. The active peptide was 2-3 times more active than Captopril in the potentiation of the effects of BK on rat arterial blood pressure and on the isolated guinea pig ileum. It also showed marked capacity to inhibit angiotensin I-converting enzyme.
Asunto(s)
Venenos de Crotálidos/farmacología , Péptidos/farmacología , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Bradiquinina/farmacología , Venenos de Crotálidos/química , Femenino , Liofilización , Cobayas , Íleon/efectos de los fármacos , Técnicas In Vitro , Masculino , Peso Molecular , Contracción Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Péptidos/aislamiento & purificación , RatasRESUMEN
Using pharmacological preparations suitable for assay of mammalian kinins, it was shown that Bothrops jararaca (Bj) venom and other kininogenases were unable to release kinins from snake plasma. The kallikrein-kinin system presents species-specificity in birds. In order to detect such a specificity in snakes, the effects of Bj venom on snake blood pressure and the effect of incubates of snake plasma with trypsin, on snake blood pressure and snake uterus, were studied. The possibility of activating snake plasma kallikrein with ellagic acid, glass beads or kaolin was also investigated. Whereas plasma of the snakes Waglerophis merremii (Wm) and Crotalus durissus (Cd), were shown to contain factor XII, prekallikrein, kininogen, kininases and to present a low but definite activation rate of the kinin system, the plasmas of Bj, Bothrops mojeni (Bm) and Oxyrophus trigeminus (Ot), yielded only kininogen and kininases. Activation of the system was not even detected by the sensitive substrate Ac-Phe-Arg-Nan (acetyl-phenylalanyl-arginyl-4nitro-anilide), indicating that the plasma of these species does not possess either factor XII and/or prekallikrein. Snake plasma may constitute an interesting model for the study of blood clotting, fibrinolytic and complement systems.
Asunto(s)
Calicreínas/sangre , Cininas/sangre , Serpientes/sangre , Animales , Biotransformación/efectos de los fármacos , Presión Sanguínea/efectos de los fármacos , Columbidae , Venenos de Crotálidos/farmacología , Ácido Elágico/farmacología , Femenino , Vidrio , Antagonistas de los Receptores Histamínicos/farmacología , Humanos , Técnicas In Vitro , Caolín/farmacología , Masculino , Tripsina/farmacología , Útero/efectos de los fármacos , Útero/metabolismoRESUMEN
1. Bothrops jararaca venom (BJV) caused a fall in the carotid artery blood pressure of the anaesthetized snake. This effect was tachyphylactic and was potentiated by captopril, a kininase II inhibitor; it was partially antagonized by promethazine plus cimetidine and was not affected by atropine. 2. Similar hypotensive effects were obtained by administration of trypsin or a partially purified BJV kininogenase to the snake. 3. Incubation of Bothrops jararaca plasma (BJP) with trypsin released a substance (or substances) that produced hypotension in the snake but not in the rat; this hypotensive effect was also potentiated by captopril. 4. The trypsinised plasma contracted Bothrops jararaca isolated uterus, a pharmacological preparation weakly sensitive to bradykinin. Trypsinised plasma was inactive on pigeon oviduct and rat uterus and displayed a weak action on the guinea-pig ileum. Similar effects were observed with incubates of a fraction of BJP, containing globulins, with a partially purified BJV kininogenase. 5. Like mammalian kinins, the substance(s) was(were) dialysable, thermostable in acid but not in alkaline pH, and inactivated by chymotrypsin but not by trypsin. Its(their) inactivation by BJP or BJP kininase II was inhibited by captopril. 6. These findings strongly suggest that, besides releasing histamine, BJV or trypsin release a kininlike substance (or substances) from the snake plasma. 7. Since BJV and other kininogenases active on mammalian plasma were shown to be unable to release kinins from BJP, in experiments conducted on pharmacological preparations suitable for the assay of mammalian kinins, these data also suggest that the snake Bothrops jararaca, like birds, may have developed its own kallikrein-kinin system.