Venom Concentrations Research Articles

A sensitive enzyme-linked immunosorbent assay for evaluating the concentration of bee venom in rat plasma.

A simple and reproducible enzyme-linked immunosorbent assay (ELISA) was developed to determine the concentration of bee venom in rat plasma. The intra- and inter-assay coefficients of variation for the ELISA were less then 3% between 0.1 and 1,000 ng mL(-1) venom, and the sensitivity of the detection was 0.1 ng mL(-1). Total recovery of the bee venom added to rat plasma was determined. Using this ELISA, serum levels of bee venom were easily determined. The rats were administered a single intravenous injection or oral dose of bee venom (1 mg kg(-1) of body weight). The bioavailability of the bee venom under the two administrations was compared using pharmacokinetic parameters. Results showed that intravenous administration of bee venom produced high plasma concentrations with a short half-life. The area under the curve for oral administration was 10 times lower than for intravenous administration. This loss of bee venom may be due to the degradation that occurs in the enzymatic and acidic environment of the gastrointestinal tract.

Kinetic Evaluation of Cell Membrane Hydrolysis during Apoptosis by Human Isoforms of Secretory Phospholipase A2

Some isoforms of secretory phospholipase A2 (sPLA2) distinguish between healthy and damaged or apoptotic cells. This distinction reflects differences in membrane physical properties. Since various sPLA2 isoforms respond differently to properties of artificial membranes such as surface charge, they should also behave differently as these properties evolve during a dynamic physiological process such as apoptosis. To test this idea, S49 lymphoma cell death was induced by glucocorticoid (6-48 h), thapsigargin (3-4 h) or calcium ionophore. Rates of membrane hydrolysis catalyzed by various concentrations of snake venom and human groups IIa, V, and X sPLA2 were compared after each treatment condition. The data were analyzed using a model that evaluates the adsorption of enzyme to the membrane surface and subsequent binding of substrate to the active site. Results were compared temporally to changes in membrane biophysics and composition. Under control conditions, membrane hydrolysis was confined to the few unhealthy cells present in each sample. Increased hydrolysis during apoptosis and necrosis appeared to reflect substrate access to adsorbed enzyme for the snake venom and group X isoforms corresponding to weakened lipid-lipid interactions in the membrane. In contrast, apoptosis promoted initial adsorption of human groups V and IIa concurrent with phosphatidylserine exposure on the membrane surface. However, this observation was inadequate to explain the behavior of the groups V and IIa enzymes toward necrotic cells where hydrolysis was reduced or absent. The response to endoplasmic reticulum stress (thapsigargin) was intermediate between that observed for glucocorticoid and ionomycin. Thus, a combination of changes in cell membrane properties during apoptosis and necrosis capacitates the cell for hydrolysis differently by each isoform.

A simple 3-day “rush” venom immunotherapy protocol: documentation of safety

Background Venom immunotherapy (VIT) is the only effective treatment for hymenoptera hypersensitivity, but conventional protocols require a few weeks. Objective We present the safety of a 3-day “rush” protocol that requires only 7 injections and 255 mgr cumulative dose before the 100 μg maintenance dose. Methods Forty-nine patients (33 males, 16 females) of mean age 43.57±12.9yrs received “rush” VIT. Only 7 injections were required until the maintenance dose of 100 mgr was reached on Day 5. On Day 1, four injections were administered with initial dose of 5 mgr and total dose of 75 μg. On Day 3 a cumulative dose of 180 mgr was administered in three injections (40 mgr, 60 mgr and 80 mgr). A dose of 100 mgr was administered on Day 5. Twenty-nine individuals were treated with Honey-Bee venom; 18 with Common wasp; 5 with Paper Wasp; while 13 patients received Mixed Vespid preparation. Inclusion criteria were documented IgE-mediated allergy with intradermal sensitivity to ≤0.1 mgr/ml venom concentration and concomitant detection of specific venom IgE ≥0.35 kU/l. Results All patients reached the maintenance dose. Forty-nine patients received 65 immunotherapy courses, resulting in 1520 injections. Thirty-three systemic reactions: 7 during building phase (1.5%); and 26 in the maintenance dose (2.4%) were observed in 9 patients. The percentage of reactions/total injection number was 2.2%; all reactions were mild-to-moderate. Fourteen patients reported documented field stings at least two months after VIT onset with only one reported mild systemic reaction. Conclusion We propose a simple “rush” VIT protocol in an outpatient setting as an easy-to-perform alternative option for VIT induction phase.

Basophil activation test in the diagnosis of insect venom allergies

Basophil activation test in the diagnosis of insect venom allergies

Renal kinetics of Bothrops alternatus (Urutu) snake venom in rats

The renal kinetics of Bothrops alternatus venom (0.8 mg/kg, i.v.) was studied in conscious male Wistar rats. Blood, urine and renal tissue samples were collected at various intervals after envenoming. Venom was quantified by ELISA in serum, renal tissue and urine. Urine volume was measured and the urine assayed for urobilinogen, glucose, bilirubin, ketones, urine specific gravity, occult blood, pH, protein, nitrite and leucocytes. Circulating venom showed biexponential kinetics, with no venom being detected after 7 days post-venom. Venom was detected in renal tissue 30 min post-venom but decreased progressively thereafter, in parallel with serum venom concentrations. Immunohistochemistry detected venom in glomeruli, proximal and distal tubules, and vascular and perivascular tissue. Venom was detected in urine 3, 6 and 24 h post-venom. Oliguria occurred 3 h to 7 days post-venom, urine acidification occurred 3–6 h post-venom, urine specific gravity increased in the first 3 h and proteinuria was also greatest in this period. Creatinine clearance decreased progressively until 24–48 h post-venom, then returned to normal. Glucose, ketones, leucocytes and occult blood were detected mainly during the first 6 h post-venom. These results indicate reversible alterations in renal function, with renal elimination of the venom.

A turbidimetric assay for the measurement of clotting times of procoagulant venoms in plasma

Introduction Assessment of the procoagulant effect of snake venoms is important for understanding their effects. The aim of this study was to develop a simple automated method to measure clotting times to assess procoagulant venoms. Methods A turbidimetric assay was developed which monitors changes in optical density when plasma and venom are mixed. Plasma was added simultaneously to venom solutions in a 96 well microtitre plate. After mixing, the optical density at 340 nm was monitored in a microplate reader every 30 s over 30 min. The clotting time was defined as the lag time until the absorbance sharply increased. The turbidimetric method was compared to manual measurement of the clotting time defined as the time when a strand of fibrin can be drawn out of the mixture. The two methods were done simultaneously, with the same venom and plasma, and compared by plotting the manual versus turbidimetric clotting times. Within-day and between-day runs were done and the coefficient of variation (CV) was calculated. Results Plots comparing manual clotting times to the lag time in the turbidimetric assay showed good correlation between the two methods for brown snake ( Pseudonaja textilis) venom, including 24 determinations in triplicate over six days for seven different venom concentrations. Good correlation was also found for four other venoms: tiger snake ( Notechis scutatus), Carpet viper ( Echis carinatus), Russell's viper ( Daboia russelii) and Malaysian pit piper ( Calloselasma rhodostoma). Between-day CV was in the range 10–20% for both methods, while within-day CV < 10%. Discussion The turbidimetric assay appears to be a simple and convenient automated method for the measurement of clotting times to assess the effects of procoagulant venoms.

Antivenom for Critically Ill Children with Neurotoxicity from Scorpion Stings

Clinically significant scorpion envenomation by Centruroides sculpturatus produces a dramatic neuromotor syndrome and respiratory insufficiency that often necessitate intensive supportive care. We hypothesized that a scorpion-specific F(ab')(2) antivenom would promptly resolve clinical symptoms in children with this syndrome. In a randomized, double-blind study, the efficacy of scorpion-specific F(ab')(2) antivenom, as compared with placebo, was assessed in 15 children 6 months to 18 years of age who were admitted to a pediatric intensive care unit with clinically significant signs of scorpion envenomation. The primary end point was the resolution of the clinical syndrome within 4 hours after administration of the study drug. Secondary end points included the total dose of concomitant midazolam for sedation and quantitative plasma venom levels, before and after treatment. The clinical syndrome resolved more rapidly among recipients of the antivenom than among recipients of placebo, with a resolution of symptoms in all eight antivenom recipients versus one of seven placebo recipients within 4 hours after treatment (P=0.001). More midazolam was administered in the placebo recipients than in the antivenom recipients (mean cumulative dose, 4.61 vs. 0.07 mg per kilogram of body weight; P=0.01). Plasma venom concentrations were undetectable in all eight antivenom recipients but in only one placebo recipient 1 hour after treatment (P=0.001). Among critically ill children with neurotoxic effects of scorpion envenomation, intravenous administration of scorpion-specific F(ab')(2) antivenom resolved the clinical syndrome within 4 hours, reduced the need for concomitant sedation with midazolam, and reduced the levels of circulating unbound venom. (ClinicalTrials.gov number, NCT00685230.)

Evaluation of the Cytogenetic Status of Human Lymphocytes After Exposure to a High Concentration of Bee Venom In Vitro

Several studies have reported radioprotective, antimutagenic, anti-inflammatory, antinociceptive, and anticancer effects of bee venom both in the cell and the whole organism. The aim of this study was to assess the effects of a single high dose of 100 microg mL(-1) of whole bee venom in human lymphocytes in vitro over a variety of time spans (from 10 min to 24 h). After the treatment, we used the comet assay and micronucleus test to see the effect of bee venom on the cell. The comet assay confirmed that the venom damaged the DNA molecule. Tail length, tail intensity, tail moment showed a significant increase (P < 0.05). The percentage of long-tailed nuclei (LTN) with the tail length exceeding the 95th percentile also increased in a time-dependent manner. The micronucleus parameters (number of micronuclei, nucleoplasmic bridges, and nuclear buds) also showed a significant time-dependent increase (P < 0.05). This research indicates that high concentrations of bee venom can lead to cellular instability. Further research is needed to understand the mechanism of action of bee venom and its components in human cells and to see if this natural product may find application in medicine.

Acute hepatotoxicity of Crotalus durissus terrificus (South American rattlesnake) venom in rats

Venom of the South American rattlesnake, Crotalus durissus terrificus (Cdt), presents myotoxic and neurotoxic outcomes, but reports on its effects on the liver are scarce. This study examined the hepatotoxicity resulting from Cdt venom administration (100, 200 and 300 µg/kg) in male Wistar rats. Animals were studies at 3, 6, 9 and 12 hours after venom injection. The hepatotoxicity was assessed through serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AP), gamma glutamyl transferase (GGT), bilirrubin and also by histopathological evaluation. All the different concentrations of Cdt venom resulted in increased levels of hepatic enzymes, when compared with the control group, except for the 100 µg/kg dose, which presented normal levels at 9 and 12 hours after venom administration. Bilirrubin levels remained unchanged by Cdt venom. Histological analysis revealed endothelial damage, inflammatory cell infiltration, as well as sinusoidal and portal congestion. Based on these observations, we may conclude that Cdt venom causes dose- and time-dependent hepatic damage in rats, characterized by elevated hepatic enzyme levels and histological alterations.

Role of serotonergic mechanism in gastric contractions induced by Indian red scorpion (Mesobuthus tamulus) venom

Aim:Gastric dysfunctions are commonly seen after scorpion envenomation, and the underlying mechanisms are not clear. Therefore, the present study was undertaken to investigate the effect of Indian red scorpion (Mesobuthus tamulus, MBT) venom on gastric fundus muscle contraction and the underlying mechanisms involved.Materials and Methods:In vitro isometric contraction was recorded from gastric fundus muscle strips on a chart recorder. The tissue was exposed to different concentrations of serotonin or crude MBT venom. The contractile responses to venom were expressed as the percentage of maximum contraction produced by serotonin at the beginning of each experiment. The contractile responses to 1.0 μg/ml of crude MBT venom were ascertained in the absence or presence of serotonin antagonist, methysergide.Results:Serotonin produced concentration-dependent fundus contractions (0.004–4.0 μM), and maximum contractile response was observed at 4.0 μM of serotonin. Hence, the contractile response obtained at 4.0 μM of serotonin was taken for normalization. The crude MBT venom (0.1–1.0 μg/ml) produced a concentration-dependent increase in fundus contractions (as % of maximum fundus contraction produced by serotonin at 4.0 μM). The maximum response was observed at 1.0 μg/ml of crude venom and a further increase in the concentration, up to 3.0 μg/ml, did not increase the response. In a separate series of experiments, pre-treatment with methysergide (1.0 μM) significantly attenuated the contractile response elicited by the venom (1.0 μg/ml) (P<0.05) and blocked the serotonin (4.0 μM) response.Conclusion:The results suggest that the crude MBT venom produces gastric fundus contractions by partially involving serotonin.

Serum levels and urine detection of Centruroides sculpturatus venom in significantly envenomated patients

Introduction. Envenomation by Centruroides sculpturatus can cause systemic signs and symptoms requiring treatment. The toxicokinetics of C. sculpturatus venom has not been described. Methods. Venom components were separated for cross-reactivity testing. Serum and urine collected from three patients envenomated by C. sculpturatus had venom levels determined by sandwich enzyme-linked immunosorbent assay (ELISA). Results. Western blot analysis indicated recognition of C. sculpturatus venom by Alacramyn®, an equine F(ab′)2 antivenom developed against Centruroides scorpion venoms, including C. sculpturatus. Serum venom levels in ng/mL with post-envenomation times in minutes (min) were as follows: 85-year-old woman = 8.2 (∼150), 2.8 (515), 1.6 (1,200); 14-month-old girl = 29.7 (∼50), 5.0 (729); 3-year-old girl = 11.1 (∼313), urine venom level of 9.0 (∼490). Conclusion. There is sufficient venom cross-antigenicity among different Centruroides species to allow this ELISA technique with Alacramyn® to determine serum and urine C. sculpturatus venom concentrations in envenomated patients.

Dialyzed venom skin tests for identifying yellow jacket-allergic patients not detected using standard venom

The chance of a nonspecific intradermal skin test response at venom concentrations greater than 1.0 microg/mL limits the diagnostic range and can interfere with the diagnosis of some affected patients. To compare the diagnostic ranges and clinical detection rates of skin tests using dialyzed yellow jacket venom (DYJV) and undialyzed YJV (UYJV), particularly in patients who have had negative venom skin test results. Both DYJV and UYJV from the same original lot were diluted from 100 microg/mL to skin test concentrations of 0.01, 0.1, 1.0, 3.0, and 10 microg/mL. Participants included 10 nonallergic controls, 20 patients with a positive history and positive skin test results using UYJV, and 24 patients with a positive history but negative skin test results using UYJV (17 of whom had a positive IgE anti-YJV serology). Dialyzed venom skin test results were positive at 10 microg/mL or less in 79% of patients with a positive history but negative skin test reactions using UYJV. The dialyzed venom skin test results showed a half-log shift to the left from the undialyzed venom results in linear regression analysis, indicating a greater detection rate with skin tests using DYJV. Results of skin tests with dialyzed venom were positive in 3 of 4 patients who had negative undialyzed venom skin test results and who experienced a systemic reaction to challenge stings. The DYJV improves the ability of skin tests to detect yellow jacket allergy and should be subject to further study.

Intersexual variations in the pharmacological properties of Coremiocnemis tropix (Araneae, Theraphosidae) spider venom

This study aimed to determine the biochemical, insecticidal and neurotoxic properties of venom from both sexes of the Australian spider Coremiocnemis tropix (Araneae, Theraphosidae). Insecticidal properties were tested in crickets, while in vitro neurotoxicity was determined in an avian skeletal muscle preparation. Some intersexual differences in venom composition were identified by rp-HPLC and by LC–MS, but the majority of components were found in venoms of both sexes. Injecting the venom into crickets revealed that venom from male specimens was slightly more potent, while female venom induced more prominent effects in the chick biventer cervicis nerve–muscle preparation. The results from the chick assay suggest the presence of at least two vertebrate-active neurotoxins. A pre-synaptic neurotoxin may explain the reversible inhibition of muscle twitches and the unaffected response to nicotinic agonists at medium concentrations of female and medium to high concentrations of male venom. In addition, the presence of a neurotoxin that blocks post-synaptic nicotinic receptors might explain the irreversible inhibition of muscle twitches and the reduced response to nicotinic agonists at high concentrations (5–10 μg/ml) of venom from female specimens only.

Milking and partial characterization of venom from the Brazilian spider Vitalius dubius (Theraphosidae)

The theraphosid spider genus Vitalius contains several species found in southeastern Brazil. In this work, we used electrostimulation to obtain venom from Vitalius dubius and examined its general composition. Male spiders yielded significantly less ( p < 0.05) venom (12.5 ± 0.7 mg of liquid/spider, n = 16; mean ± S.E.M.) than female spiders (25.5 ± 2.0 mg of liquid/spider, n = 11). However, when corrected for spider weight, males yielded slightly more venom (2.89 ± 0.16 mg/g vs. 2.45 ± 0.76 mg/g for males and females, respectively, p < 0.05). Venom yield correlated linearly with spider weight for spiders weighing up to ∼12–13 g, but decreased in very heavy females. There was a marked decrease in venom yield after the first milking. The protein concentration of pooled venom was 18.3 ± 2.4 mg/ml ( n = 4) and accounted for 16.6 ± 4.7% of the dry venom weight. The venom contained high hyaluronidase activity (275 ± 24 TRU/mg of protein, n = 4), with a molecular mass of ∼45 kDa estimated by zymography. SDS-PAGE revealed a few proteins with molecular masses >14 kDa but showed two staining bands of peptides <14 kDa. The venom reacted in ELISA with affinity-purified IgG from commercial arachnidic antivenom. Immunoblotting with this IgG detected proteins of 30–140 kDa only. Fractionation of the venom by reverse-phase chromatography resulted in five major and eight minor peaks.

Isolation of 5-Hydroxytryptamine from the Venom of the Indian Red Scorpion (Mesobuthus tamulus)

The present study was undertaken to isolate 5-hydroxytryptamine (5-HT) from crude Indian red scorpion (Mesobuthus tamulus; MBT) venom as it has not been reported yet. Therefore, with the help of bioassay (using gastric fundus contractions) and fluorimetric assay methods, the 5-HT content of crude MBT venom (CV) was determined. The concentration of 5-HT in CV by either of the methods was different (117 times). Further, a 5-HT antagonist methysergide partially blocked the CV-induced gastric fundus contractions. Hence, for isolation and determination of 5-HT in crude MBT venom, CV was subjected to Sephadex gel (G 75-125) filtration chromatography. The eluates were screened for op- tical density (OD) at 280 nm, lethality and gastric fundus contractions. Two peaks of enhanced gastric fundus contractions were observed between 26-70 ml and 90 -110 ml of eluate volumes. As the first peak (between 26-70 ml) eluates exhib- ited high OD and lethality, further analysis was not undertaken. The second peak (between 90-110 ml) eluates exhibited very low OD and were non-lethal. On bioassay, the 5-HT content of pooled eluates of second peak was 0.0398 ± 0.008 � g/ml and by fluorimetric assay it was 0.0396 ± 0.007 � g/ml. The 5-HT concentration of crude MBT venom per unit mass was 0.0175 ± 0.0035 �g/mg by bioassay and 0.0174 ± 0.0031 �g/mg by fluorimetric assay. Further, the gastric fundus contractions elicited by second peak eluates were blocked by methysergide (1.0 �M). Thus, the second peak eluates of crude MBT venom contain 5-HT and its concentration was about 0.0174 � g/mg.

Genotoxic potential of bee venom (Apis Mellifera) on human peripheral blood lymphocytes in vitro using single cell gel electrophoresis assay

Bee venom (BV) has been known to have therapeutic applications in traditional medicine to treat variety of diseases. It is also known that bee venom possesses anti-inflammatory and anticancer effects and that it can inhibit proliferation and induces apoptosis in cancer cells, but there is lack of information regarding genotoxicity of whole bee venom on normal human cells. In the present study, peripheral blood human lymphocytes from healthy donor were exposed in vitro to different concentration (5, 10, 25, 50 and 100 μ g/mL) of whole bee venom at different time periods (1, 6 and 24 hours). The single cell gel electrophoresis (SCGE) assay was used to evaluate the genotoxicity towards human cells. Results showed statistically significant increase in DNA damage caused in BV treated human lymphocytes compared to corresponding control cells for the tail length and tail moment. These results show that the extent of DNA damage, determined by the use of single cell gel electrophoresis is time and dose dependent. Based on the results it is clear that whole bee venom induces DNA damage and has genotoxic potential on human peripheral blood lymphocytes in vitro.

Neutralization of the pharmacological effects of Cobra and Krait venoms by chicken egg yolk antibodies

Five-month-old white leghorn chickens were immunized with 50 μg of Common Cobra ( Naja naja) and 30 μg of Krait venoms ( Bungarus caeruleus) to generate antivenom antibodies against the venom antigen. Chickens received booster doses of increasing concentrations of venom at 14 days time intervals to raise the antivenom level in egg yolk. The antivenom from immunized chicken egg yolk was extracted by polyethylene glycol (PEG) and ammonium sulphate precipitation method which was further purified by DEAE cellulose ion exchange column chromatography. A high molecular weight protein of 180 kDa was detected by electrophoretic analysis which shows the purity of antivenom generated in chicken. Antibodies generated were specific and sensitive to the venom antigen. Various pharmacological activities of Cobra and Krait venoms were carried out by both in-vivo and in-vitro methods. The neutralization of lethality, hemorrhagic, edema, PLA 2 and procoagulant activity was evaluated in assays involving pre-incubation of venom and antivenom prior to testing. The antivenom was effective in neutralizing the toxic and enzymatic activities of venom. The LD 50 of venom for 18 g of mice was found to be 10 μg for Cobra and 3 μg for Krait venoms. The median effective dose (ED 50) of anti-Cobra venom was 4.48 mg/5LD 50 and 1.0 ml neutralized 0.127 mg of Cobra venom and the median effective dose (ED 50) of anti-Krait venom was 3.18 mg/5LD 50 and 1.0 ml neutralized 0.051 mg of Krait venom. The results indicate that antivenom generated in chicken could be used for therapeutic purposes in case of snakebite envenomation.

Effectiveness of pressure‐immobilization first aid for snakebite requires further study

In the prospective Royal Darwin Hospital snakebite study, pressure-immobilization first aid (PI) was used more often than in previous studies. However, bandages were not uncommonly too loose or not applied to the whole limb and immobilization was often neglected. While PI should continue to be promoted as the standard for Australia for the present, prospective multicentre studies of snakebite with quantitative assays for blood venom concentration will hopefully better elucidate the real effectiveness of PI and define the limitations of timing of application and determine the optimum types of bandage materials to use and the pressure required to be maintained.

Studies on pharmacological effects of Russell's viper and Saw-scaled viper venom and its neutralization by chicken egg yolk antibodies

Antivenom antibodies were raised in 24-week-old white leghorn chickens against hemotoxic venoms of Russell's viper and Saw-scaled viper snakes. Booster injections of increasing concentrations of venom were given at 14days of time interval to raise the antivenom level in egg yolk. Antibodies were extracted from immunized chicken egg yolk by Polson et al. (Polson A., Von Wechmar M.B., Van Regenmortel M.H.V. Isolation of viral IgY antibodies from yolks of immunized hens. Immunological Communications 1980; 9:475–493.) and further purified by DEAE cellulose ion exchange column chromatography, which gave pure (180–200kDa) specific antibodies against venom. High titre of more than 1:10,000 antibodies were detected by ELISA at the 135th day of observation. The lethal toxicity and various pharmacological activities like hemorrhagic activity, phospholipase activity, edema and procoagulant activities of venom were carried out by both in vivo and in vitro methods. The effectiveness of antivenom in neutralizing these effects was carried out involving pre-incubation type experiments. The median effective dose (ED 50) for Russell's viper venom was 0.96mg/2LD 50/18g mice and for Saw-scaled viper venom it was 1.28mg/2LD 50/18g mice. One millilitre of specific antivenom was effective in neutralizing 0.110mg of Russell's viper and 0.137mg of Saw-scaled viper venoms respectively (PD 50). Antivenom was effective in neutralization assays in a dose dependent manner. The results indicate that antibodies raised in chicken could effectively neutralize the pharmacological effects induced by venoms and chickens therefore present an alternative and cheaper source of specific antibody generation.

Mass spectrometry analysis, amino acid sequence and biological activity of venom components from the Brazilian scorpion Opisthacanthus cayaporum

This communication reports the separation of 80 fractions from the venom of the Ischnuridae scorpion Opisthacanthus cayaporum by high-performance liquid chromatography (HPLC). From these, 93 distinct components were identified by liquid chromatography/electrospray mass spectrometry (LC/ESI-MS) analysis, with molecular weights varying from 229.2 to 61,144.0 atomic mass units. Additionally, the HPLC fractions were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) which resulted in 221 distinct components, among which were 52 of the 93 obtained by LC/ESI-MS. The entire set of different molecular species found (total of 262 molecular masses) has a trimodal molecular weight distribution, with 42% of the components possessing 229.2–2985.3 Da, 37% within the range of 3045.0–7258.6 Da and 12% within the range 7458.4–9429 Da. Seventeen peptides/proteins were isolated and were sequenced by Edman degradation, among which were a scorpine-like peptide (8315 Da), presenting antimicrobial activity, and two phospholipase A2 with a molecular weight around 14 kDa. The pharmacological effects of the venom were tested on isolated rat and insect (cockroach) nerves using the single sucrose-gap assay. The ED50 of the venom was 1.1 mg/ml in insect nerves. Venom concentrations in the order of 3 mg/ml causes only 9% reduction of compound action potentials (APs) of rat nerves, suggesting that this venom is rather specific for insects. Comparative analysis of venom from male and female O. cayaporum was performed by HPLC and MALDI-TOF-MS showing no qualitative variations, but rather quantitative differences among both samples.