RESUMO
Rhinella marina toad is abundant in Brazil. Its poison contains cardiac glycosides called bufadienolides, which are extensively investigated for their bioactivity. Our aim was to characterize the vasoactivity of Rhinella marina poison (RmP) on the aorta of male Wistar rats. For this, the RmP was first collected and processed to obtain an alcoholic extract. To determine cardiovascular effects of RmP, we performed in vivo tests by administering RmP intravenously in doses of 0.1-0.8 mg/kg. Vascular reactivity was also performed through concentration-response curves to RmP (10 ng/mL to 200 µg/mL) in aortic segments with and without endothelium. RmP induced a concentration-dependent contraction in rat aorta which was partly endothelium-mediated. Nitric oxide contributes with this response in view that incubation with L-NAME increased the contractile response. Additionally, treatment with indomethacin [cyclooxygenase, (COX) inhibitor], nifedipine (L-type voltage-gated calcium channels blocker), and BQ-123 (ETA receptors antagonist) decreased maximum response, and ketanserin (5-HT2 receptors antagonist) decreased pEC50, suggesting active participation of these pathways in the contractile response. On the other hand, apocynin (NADPH oxidase inhibitor) did not alter contractility. Incubation with prazosin (α1-adrenergic receptor antagonist) abolished the contractile response, suggesting that the RmP-induced contraction is dependent on the adrenergic pathway. In the Na+/K+ ATPase protocol, a higher Emax was observed in the RmP experimental group, suggesting that RmP potentiated Na+/K+ATPase hyperpolarizing response. When this extract was injected (i.v.) in vivo, increase in blood pressure and decrease in heart rate were observed. The results were immediate and transitory, and occurred in a dose-dependent manner. Overall, these data suggest that the poison extract of R. marina toad has an important vasoconstrictor action and subsequent vasopressor effects, and its use can be investigated to some cardiovascular disorders.
Assuntos
Bufanolídeos , Venenos , Adenosina Trifosfatases/metabolismo , Adenosina Trifosfatases/farmacologia , Adrenérgicos/farmacologia , Antagonistas Adrenérgicos/farmacologia , Animais , Bufanolídeos/toxicidade , Bufo marinus/metabolismo , Canais de Cálcio , Endotélio Vascular , Hemodinâmica , Indometacina/farmacologia , Ketanserina/farmacologia , Masculino , Metanol/farmacologia , NADPH Oxidases , NG-Nitroarginina Metil Éster , Nifedipino/farmacologia , Óxido Nítrico/metabolismo , Prazosina/farmacologia , Prostaglandina-Endoperóxido Sintases/metabolismo , Ratos , Ratos Wistar , Serotonina/farmacologia , VasoconstritoresRESUMO
Rhinella schneideri is a common toad found in South America, whose paratoid toxic secretion has never been explored as an insecticide. In order to evaluate its insecticidal potential, Nauphoeta cinerea cockroaches were used as an experimental model in biochemical, physiological and behavioral procedures. Lethality assays with Rhinella schneideri paratoid secretion (RSPS) determined the LD50 value after 24 h (58.07µg/g) and 48 h exposure (44.07 µg/g) (R2 = 0.882 and 0.954, respectively). Acetylcholinesterase activity (AChE) after RSPS at its highest dose promoted an enzyme inhibition of 40%, a similar effect observed with neostigmine administration (p < 0.001, n= 5). Insect locomotion recordings revealed that RSPS decreased the distance traveled by up to 37% with a concomitant 85% increase in immobile episodes (p < 0.001, n = 36). RSPS added to in vivo cockroach semi-isolated heart preparation promoted an irreversible and dose dependent decrease in heart rate, showing a complete failure after 30 min recording (p < 0.001, n ≥ 6). In addition, RSPS into nerve-muscle preparations induced a dose-dependent neuromuscular blockade, reaching a total blockage at 70 min at the highest dose applied (p < 0.001, n ≥ 6). The effect of RSPS on spontaneous sensorial action potentials was characterized by an increase in the number of spikes 61% (p < 0.01). Meanwhile, there was 42% decrease in the mean area of those potentials (p < 0.05, n ≥ 6). The results obtained here highlight the potential insecticidal relevance of RSPS and its potential biotechnological application.
Assuntos
Venenos de Anfíbios/farmacologia , Bufo marinus/metabolismo , Inibidores da Colinesterase/farmacologia , Baratas/efeitos dos fármacos , Inseticidas/farmacologia , Junção Neuromuscular/efeitos dos fármacos , Glândula Parótida/metabolismo , Acetilcolinesterase/metabolismo , Venenos de Anfíbios/metabolismo , Animais , Inibidores da Colinesterase/metabolismo , Baratas/enzimologia , Relação Dose-Resposta a Droga , Feminino , Proteínas de Insetos/antagonistas & inibidores , Proteínas de Insetos/metabolismo , Inseticidas/metabolismo , Dose Letal Mediana , Locomoção/efeitos dos fármacos , Masculino , Junção Neuromuscular/enzimologia , Via SecretóriaRESUMO
A simple and rapid focused ultrasound extraction method was developed for the determination of Persistent Organic Pollutants (POPs) in liver tissue obtained of giant toad (Rhinella marina) using a gas chromatography coupled to a mass detector with electron impact ionization. The performed method for POPs, was validated in fortified matrix, showing linearity from the LOQ up to 100 ng/mL; LODs and LOQs for each compound were between 1.7 and 4.8 and 3.5-7.5 ng/mL, respectively. Recovery rates were among 79%-116% for POPs determined. Finally, the method was applied in liver samples of giant toads found in a malarial area in Mexico. The sensitivity of the proposed method was good enough to ensure reliable determination of target analytes at concentration levels commonly found in this kind of samples.
Assuntos
Bufo marinus/metabolismo , Poluentes Ambientais/metabolismo , Animais , Poluição Ambiental , Cromatografia Gasosa-Espectrometria de Massas , Limite de Detecção , Fígado/metabolismo , MéxicoRESUMO
Bufadienolides are the main active compounds in the Bufonidae family of frogs. Recent studies have demonstrated cytotoxic and/or antitumor activity in these molecules. A HPLC-DAD method was developed and validated to quantify three bufadienolides (telocinobufagin, marinobufagin and bufalin) in ethyl acetate extracts of the cane toad poison frogs and smooth-sided toad. The chromatographic analysis was performed on Phenomenex Luna C18 (250.0 × 4.6 mm, 5 µm), using gradient elution with acetonitrile and water, at a flow rate of 1.0 mL min(-1) and detection at 296 nm. The method showed linearity (r > 0.999) and adequate recovery values (86%-111%). The limits of quantification of bufadienolides were 7.4 µg mL(-1) for telocinobufagin, 4.2 µg mL(-1) for marinobufagin and 4.0 µg mL(-1) for bufalin. Intraday and interday values of the method were evaluated and presented standard deviation values lower than 5%. The method was successfully applied to quantify the bufadienolides in the venom extract of the cane toad, which showed a content of 60% of marinobufagin. The same method was not selective for the venom extract of the Rhaebo guttatus, despite being linear, accurate and precise, requiring the development of a technique that presents a greater selectivity.
Assuntos
Venenos de Anfíbios/química , Bufanolídeos/análise , Bufo marinus/metabolismo , Bufonidae/metabolismo , Cromatografia Líquida de Alta Pressão/métodos , Espectrofotometria Ultravioleta/métodos , Animais , Limite de Detecção , Reprodutibilidade dos TestesRESUMO
Glucocorticoid steroids modulate immunocompetence in complex ways with both immunoenhancing and immunosuppressive effects in vertebrates exposed to different stressors. Such bimodal effects have been associated with variation in duration and intensity of the stress response. Given that natural populations have been exposed to a multitude of stressors, a better understanding of the functional association between duration and intensity of the stress response, the resulting changes in glucocorticoid plasma levels and their impact on different aspects of immunocompetence emerges as a cornerstone for vertebrate conservation strategies. We investigated the effects of a restraint challenge (with and without movement restriction), long-term captivity, and transdermal corticosterone application on plasma levels of corticosterone (hereinafter referred to as CORT) and different parameters of innate immunocompetence in the male cururu toads (Rhinella icterica). We show that for R. icterica restraint for 24h proved to be a stressful condition, increasing CORT by 3-fold without consistent immunological changes. However, the application of a more intense stressor (restraint with movement restriction), for the same period, potentiated this response resulting in a 9-fold increase in CORT, associated with increase Neutrophil/Lymphocyte ratio (N:L) and a lower bacterial killing ability (BKA). Transdermal application of corticosterone efficiently mimics repeated acute stress response events, without changing the immune parameters even after 13 days of treatment. Interestingly, long-term captivity did not mitigate the stress response, since the toads maintained 3-fold increased CORT even after 3 months under these conditions. Moreover, long-term captivity in the same condition increased total leukocyte count (TLC) and generated an even greater decrease in BKA, suggesting that consequences of the stress response can be aggravated by time in captivity.
Assuntos
Corticosterona/administração & dosagem , Administração Cutânea , Animais , Bufo marinus/metabolismo , Corticosterona/sangue , Imunidade Inata , Imunocompetência , Técnicas Imunoenzimáticas , Contagem de Leucócitos , Linfócitos/citologia , Masculino , Neutrófilos/citologia , Restrição FísicaRESUMO
Several studies indicate that wild free-living vertebrates seasonally regulate plasma glucocorticoids. However, not only glucocorticoids but also the amount of receptors is important in determining biological responses. In this context, seasonal regulation of glucocorticoid receptor (GR) is crucial to modulate the response to glucocorticoids. Rhinella arenarum is an anuran exhibiting seasonal variations in plasma glucocorticoids and also in the number of binding sites (B(max)) of the testicular cytosolic GR. In this work, we evaluated if the annual pattern of GR protein in the testis varies seasonally and, by an in vitro approach, the role of glucocorticoids, androgens, and melatonin in the regulation of the GR B(max) and protein level. For this purpose, testes were treated with two physiological concentrations of melatonin (40 and 200 pg/ml), with or without luzindole (melatonin-receptor antagonist); with testosterone, cyanoketone (inhibitor of steroidogenesis) or casodex (androgen-receptor antagonist); or with dexamethasone or RU486 (GR antagonist). After treatments, B(max) and protein level were determined by the binding of [(3)H]dexamethasone and Western blot, respectively. Results showed that GR protein decreases in the winter. The in vitro treatment with melatonin produced a biphasic effect on the B(max) with the lowest concentration decreasing this parameter by a receptor-mediated mechanism. However, melatonin had no effect on the GR protein level. Conversely, a high concentration of dexamethasone up-regulated the GR protein and androgens neither changed the B(max) nor the protein level. These findings suggest that seasonal changes in plasma melatonin and glucocorticoids modulate the effect of glucocorticoids in the testis of R. arenarum.
Assuntos
Bufo marinus/metabolismo , Glucocorticoides/metabolismo , Receptores de Glucocorticoides/metabolismo , Testículo/metabolismo , Anilidas/farmacologia , Animais , Sítios de Ligação , Western Blotting/veterinária , Cianocetona/farmacologia , Dexametasona/farmacologia , Regulação da Expressão Gênica , Glucocorticoides/sangue , Técnicas In Vitro , Cinética , Masculino , Melatonina/metabolismo , Melatonina/farmacologia , Mifepristona/farmacologia , Nitrilas/farmacologia , Distribuição Aleatória , Receptores de Glucocorticoides/genética , Estações do Ano , Testículo/efeitos dos fármacos , Testosterona/metabolismo , Testosterona/farmacologia , Compostos de Tosil/farmacologia , Triptaminas/farmacologiaRESUMO
This study aimed to investigate the effect of dobutamine on water transport across toad bladder epithelium. Water flow through the membrane was measured gravimetrically in bladder sac preparations. Dobutamine had no effect on basal water transport, but partially inhibited transport stimulated by vasopressin. Similarly, dobutamine exerted no influence on the hydrosmotic response to 8-chlorophenylthio-cAMP, but interfered with the response to phosphodiesterase inhibitor 1-methyl-3-isobutyl-xanthine. These results demonstrate that this catecholamine may inhibit vasopressin-stimulated water transport at a site prior to cAMP formation. The use of propranolol was ineffective in blocking the effect of dobutamine on transport stimulated by vasopressin, indicating that beta-adrenoceptors play no role in this effect. On the other hand, phentolamine significantly reduced the effect of dobutamine, indicating the involvement of alpha-adrenoceptors in such event. Rauwolscine also inhibited the effect of dobutamine, pointing to the specific contribution of the alpha(2)-adrenoceptors to this effect. Taken together, the results of this study demonstrate that dobutamine inhibits vasopressin-stimulated water transport in toad bladders through a mechanism mediated by the stimulation of alpha(2)-adrenoceptors, thus suggesting that such a drug may exert a direct cellular effect on membrane permeability to water in transporting epithelia. The current study may provide a better understanding of the effects of dobutamine on renal function by contributing towards the elucidation of its action mechanism.
Assuntos
Agonistas de Receptores Adrenérgicos alfa 2 , Agonistas alfa-Adrenérgicos/farmacologia , Arginina Vasopressina/metabolismo , Bufo marinus/metabolismo , Dobutamina/farmacologia , Células Epiteliais/efeitos dos fármacos , Bexiga Urinária/efeitos dos fármacos , Água/metabolismo , 1-Metil-3-Isobutilxantina/farmacologia , Antagonistas Adrenérgicos alfa/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Animais , AMP Cíclico/análogos & derivados , AMP Cíclico/farmacologia , Células Epiteliais/metabolismo , Técnicas In Vitro , Fentolamina/farmacologia , Inibidores de Fosfodiesterase/farmacologia , Propranolol/farmacologia , Receptores Adrenérgicos alfa 2/metabolismo , Tionucleotídeos/farmacologia , Bexiga Urinária/metabolismo , Ioimbina/farmacologiaRESUMO
Resting respiratory behavior of Bufo marinus in minimally instrumented toads is described for a period of 24 hours in which the animals are left undisturbed. Torpor-related long apneas are described and their implications for blood gas levels are investigated. Results show that the resting ventilation rate of Bufo marinus is much lower than that reported so far. Levels of arterial oxygen, carbon dioxide, and pH are monitored during artificial long apneas induced by anesthesia. The toads showed an unexpected ability to unload carbon dioxide by non-respiratory means, even while being kept on dry plastic box with no access to water. Oxygen arterial partial pressure dropped to very low levels after one hour of apnea. This suggests that these animals may endure very well severe hypoxia for long periods of time while in torpor.
Assuntos
Bufo marinus/metabolismo , Respiração , Descanso/fisiologia , Animais , Gasometria , Bufo marinus/sangue , Dióxido de Carbono/sangue , Concentração de Íons de Hidrogênio , Oxigênio/sangue , Análise de RegressãoRESUMO
The aim of this work was to study the effect of some pharmacological cholinergic agents on the events that follow the interaction of arginine vasopressin with toad bladder membrane receptors related to synthesis of 3'5'(c)AMP. The water flow through the membrane was measured gravimetrically in sac preparations of the membrane. In the absence of arginine vasopressin (AVP), carbachol induced a significant increase in the water flow (37%) related to the basal (Ringer's solution). On the other hand, when carbachol and AVP were associated, a significant decrease of AVP hydrosmotic activity occurred (23%). The inhibitory effect of carbachol on the AVP action was almost completely abolished by the cholinergic antagonists atropine, pirenzepine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) and the calcium antagonist lanthanum. Similarly, when carbachol and 3'5' cyclic adenosine monophosphate (3'5'(c)AMP) were associated, a decrease of nucleotide hydrosmotic activity was observed (12.80%). This effect was partially restored by the addition of pirenzepine or 4-DAMP in the bath solution. These results suggest a role for muscarinic receptors of sub-type M(1) and M(3), which are involved in the intracellular calcium release. The increase of calcium concentration in the intracellular medium acts as a negative modulator in the hydrosmotic action of antidiuretic hormone.