Suspecting Renal Artery Thrombosis

Renal artery thrombosis is a threatening clinical diagnosis, in which renal infarction may occur. Often misdiagnosed, for mimicking other common diseases, it should be considered in persistent flank pain to improve care and reduce morbidity. We review a case of a healthy, 57 year-old woman with renal artery thrombosis mimicking pyelonephritis and renal calculus obstruction, highlighting features of this clinical condition. An accurate diagnosis is essential for optimal management and prompts treatment, which still remains to be defined.

Estimating glomerular filtration rate in kidney transplantation: Still searching for the best marker

Kidney transplantation is the treatment of choice for end-stage renal disease. The evaluation of graft function is mandatory in the management of renal transplant recipients. Glomerular filtration rate (GFR), is generally considered the best index of graft function and also a predictor of graft and patient survival. However GFR measurement using inulin clearance, the gold standard for its measurement and exogenous markers such as radiolabeled isotopes ((51)Cr EDTA, (99m)Tc DTPA or (125)I Iothalamate) and non-radioactive contrast agents (Iothalamate or Iohexol), is laborious as well as expensive, being rarely used in clinical practice. Therefore, endogenous markers, such as serum creatinine or cystatin C, are used to estimate kidney function, and equations using these markers adjusted to other variables, mainly demographic, are an attempt to improve accuracy in estimation of GFR (eGFR). Nevertheless, there is some concern about the inability of the available eGFR equations to accurately identify changes in GFR, in kidney transplant recipients. This article will review and discuss the performance and limitations of these endogenous markers and their equations as estimators of GFR in the kidney transplant recipients, and their ability in predicting significant clinical outcomes.

Epidemiology of invasive aspergillosis in critically ill patients: clinical presentation, underlying conditions, and outcomes

INTRODUCTION: Invasive aspergillosis (IA) is a fungal infection that particularly affects immunocompromised hosts. Recently, several studies have indicated a high incidence of IA in intensive care unit (ICU) patients. However, few data are available on the epidemiology and outcome of patients with IA in this setting.

Seeking transparency on allocation of kidneys from deceased donors

Kidney transplantation is the preferred treatment for many end stage renal disease patients; however, the small number of organs for transplantation does not allow all patients to have access to this scarce resource. An allocation system for deceased donor kidneys should be anchored to transparent policies and rules. It should take into account the relationship between supply and demand, hence seeking a balance between the higher net benefit of survival that can be provided by a particular organ and the transplant candidates’ waiting time (as well as the probability of being transplanted).

Oxidative stress and its haemodynamic consequences in chronic kidney disease

Chronic kidney disease (CKD) is associated with increased cardiovascular risk in comparison with the general population. This can be observed even in the early stages of CKD, and rises in proportion to the degree of renal impairment. Not only is cardiovascular disease (CVD) more prevalent in CKD, but its nature differs too, with an excess of morbidity and mortality associated with congestive cardiac failure, arrhythmia and sudden death, as well as the accelerated atherosclerosis which is also observed. Conventional cardiovascular risk factors such as hypertension, dyslipidaemia, obesity, glycaemia and smoking, are highly prevalent amongst patients with CKD, although in many of these examples the interaction between risk factor and disease differs from that which exists in normal renal function. Nevertheless, the extent of CVD cannot be fully explained by these conventional risk factors, and non-conventional factors specific to CKD are now recognised to contribute to the burden of CVD. Oxidative stress is a state characterised by excessive production of reactive oxygen species (ROS) and other radical species, a reduction in the capacity of antioxidant systems, and disturbance in normal redox homeostasis with depletion of protective vascular signalling molecules such as nitric oxide (NO). This results in oxidative damage to macromolecules such as lipids, proteins and DNA which can alter their functionality. Moreover, many enzymes are sensitive to redox regulation such that oxidative modification to cysteine thiol groups results in activation of signalling cascades which result in adverse cardiovascular effects such as vascular and endothelial dysfunction. Endothelial dysfunction and oxidative stress are present in association with many conventional cardiovascular risk factors, and can be observed even prior to the development of overt, clinical, vascular pathology, suggesting that these phenomena represent the earliest stages of CVD. In the presence of CKD, there is increased ROS production due to upregulated NADPH oxidase (NOX), increase in a circulating asymmetric dimethylarginine (ADMA), uncoupling of endothelial nitric oxide synthase (eNOS) as well as other mechanisms. There is also depletion in exogenous antioxidants such as ascorbic acid and tocopherol, and a reduction in activity of endogenous antioxidant systems regulated by the master gene regulator Nrf-2. In previous studies, circulating markers of oxidative stress have been shown to be increased in CKD, together with a reduction in endothelial function in a stepwise fashion relating to the severity of renal impairment. Not only is CVD linked to oxidative stress, but the progression of CKD itself is also in part dependent on redox sensitive mechanisms. For example, administration of the ROS scavenger tempol attenuates renal injury and reduces renal fibrosis seen on biopsy in a mouse model of CKD, whilst conversely, supplementation with the NOS inhibitor L-NAME causes proteinuria and renal impairment. Previous human studies examining the effect of antioxidant administration on vascular and renal function have been conflicting however. The work contained in this thesis therefore examines the effect of antioxidant administration on vascular and endothelial function in CKD. Firstly, 30 patients with CKD stages 3 – 5, and 20 matched hypertensive controls were recruited. Participants with CKD had lower ascorbic acid, higher TAP and ADMA, together with higher augmentation index and pulse wave velocity. There was no difference in baseline flow mediated dilatation (FMD) between groups. Intravenous ascorbic acid increased TAP and O2-, and reduced central BP and augmentation index in both groups, and lowered ADMA in the CKD group only. No effect on FMD was observed. The effects of ascorbic acid on kidney function was then investigated, however this was hindered by the inherent drawbacks of existing methods of non-invasively measuring kidney function. Arterial spin labelling MRI is an emerging imaging technique which allows measurement of renal perfusion without administration of an exogenous contrast agent. The technique relies upon application of an inversion pulse to blood within the vasculature proximal to the kidneys, which magnetically labels protons allowing measurement upon transit to the kidney. At the outset of this project local experience using ASL MRI was limited and there ensued a prolonged pre-clinical phase of testing with the aim of optimising imaging strategy. A study was then designed to investigate the repeatability of ASL MRI in a group of 12 healthy volunteers with normal renal function. The measured T1 longitudinal relaxation times and ASL MRI perfusion values were in keeping with those found in the literature; T1 time was 1376 ms in the cortex and 1491 ms in the whole kidney ROI, whilst perfusion was 321 mL/min/100g in the cortex, and 228 mL/min/100g in the whole kidney ROI. There was good reproducibility demonstrated on Bland Altman analysis, with a CVws was 9.2% for cortical perfusion and 7.1% for whole kidney perfusion. Subsequently, in a study of 17 patients with CKD and 24 healthy volunteers, the effects of ascorbic acid on renal perfusion was investigated. Although no change in renal perfusion was found following ascorbic acid, it was found that ASL MRI demonstrated significant differences between those with normal renal function and participants with CKD stages 3 – 5, with increased cortical and whole kidney T1, and reduced cortical and whole kidney perfusion. Interestingly, absolute perfusion showed a weak but significant correlation with progression of kidney disease over the preceding year. Ascorbic acid was therefore shown to have a significant effect on vascular biology both in CKD and in those with normal renal function, and to reduce ADMA only in patients with CKD. ASL MRI has shown promise as a non-invasive investigation of renal function and as a biomarker to identify individuals at high risk of progressive renal impairment.

Linfócitos T : uma análise do perfil diferencial da expressão gênica na imunorregulação

Tese (doutorado)—Universidade de Brasília, Faculdade de Medicina, Pós-Graduação em Patologia Molecular, 2016.

Postnatal Evaluation and Outcome of Prenatal Hydronephrosis

Background: Prenatal hydronephrosis (PNH) is dilation in urinary collecting system and is the most frequent neonatal urinary tract abnormality with an incidence of 1% to 5% of all pregnancies. PNH is defined as anteroposterior diameter (APD) of renal pelvis ≥ 4 mm at gestational age (GA) of < 33 weeks and APD ≥ 7 mm at GA of ≥ 33 weeks to 2 months after birth. All patients need to be evaluated after birth by postnatal renal ultrasonography (US). In the vast majority of cases, watchful waiting is the only thing to do; others need medical or surgical therapy. Objectives: There is a direct relationship between APD of renal pelvis and outcome of PNH. Therefore we were to find the best cutoff point APD of renal pelvis which leads to surgical outcome. Patients and Methods: In this retrospective cohort study we followed 200 patients 1 to 60 days old with diagnosis of PNH based on before or after birth ultrasonography; as a prenatal or postnatal detected, respectively. These patients were referred to the nephrology clinic in Zahedan Iran during 2011 to 2013. The first step of investigation was a postnatal renal US, by the same expert radiologist and classifying the patients into 3 groups; normal, mild/moderate and severe. The second step was to perform voiding cystourethrogram (VCUG) for mild/moderate to severe cases at 4 - 6 weeks of life. Tc-diethylene triamine-pentaacetic acid (DTPA) was the last step and for those with normal VCUG who did not show improvement in follow-up examination, US to evaluate obstruction and renal function. Finally all patients with mild/moderate to severe PNH received conservative therapy and surgery was preserved only for progressive cases, obstruction or renal function ≤35%. All patients’ data and radiologic information was recorded in separate data forms, and then analyzed by SPSS (version 22). Results: 200 screened PNH patients with male to female ratio 3.5:1 underwent first postnatal control US, of whom 65% had normal, 18% mild/moderate and 17% severe hydronephrosis. 167 patients had VCUG of whom 20.82% with VUR. 112 patients performed DTPA with following results: 50 patients had obstruction and 62 patients showed no obstructive finding. Finally 54% of 200 patients recovered by conservative therapy, 12.5% by surgery and remaining improved without any surgical intervention. Conclusions: The best cutoff point of anteroposterior renal pelvis diameter that led to surgery was 15 mm, with sensitivity 88% and specificity 74%.

Caractérisation de différents mécanismes immunologiques conduisant au dommage glomérulaire chez le greffé rénal avec rejet humoral; les effets des anticorps anti-HLA sur l’expression endothéliale et les niveaux sériques de thrombomoduline chez les patients transplantés

La greffe rénale est le meilleur traitement de l’insuffisance rénale terminale. Par contre, la perte prématurée du greffon est un problème majeur chez les greffés qui est due majoritairement au rejet. La classification de Banff reconnait 2 catégories de rejets : une réaction médiée par les anticorps (ABMR) et/ou une réaction cellulaire (TCMR). L’ABMR est caractérisé par le développement de novo d’anticorps contre le donneur (DSA) en circulation et des dommages histologiques, comme la glomérulopathie du transplant. De novo, les DSA anti-HLA-II sont plus fréquemment associés à la glomérulopathie du transplant que les anti-HLA-I et sont associés à un moins bon pronostic clinique. Toutefois, le mécanisme par lequel les anti-HLA-II sont plus dommageables demeure mal connu. Mon hypothèse est que les anticorps anti-HLA sont suffisants pour perturber l’hémostase de l’endothélium glomérulaire. Plus particulièrement, nous croyons que les anticorps anti-HLA-II, diminuent l’expression de la thrombomoduline (TBM), ce qui pourrait mener aux lésions endothéliales glomérulaires associées à la glomérulopathie du transplant. Pour évaluer cette hypothèse, j’ai utilisé un modèle in vitro d’endothélium glomérulaire humain et du sérum de patients transplantés rénaux. Nous avons observé que l’expression membranaire de la TBM augmentait de manière dosedépendante en présence d‘anti-HLA-I, mais pas anti-HLA-II. Toutefois, lors de la mesure intracellulaire nous avons observé une accumulation cytosolique en réponse à une stimulation par les anti-HLA-II. De plus, nous avons observé une association significative entre la présence de DSA circulants anti-HLA-II dans les patients transplantés rénaux et un faible taux de TBM sérique. Ces résultats indiquent que la liaison des anticorps anti-HLA-I et II produit des effets différents sur l’expression endothéliale de la TBM. Les anticorps anti-HLA-II pourraient être associés à un état prothrombotique qui pourrait expliquer l’occurrence plus élevée de lésions microangiopathiques dans l’allogreffe et la moins bonne condition observée chez les patients ayant ces anticorps.

New prophylactic and therapeutic treatments to combat pathogenic Enterohaemorrhagic Escherichia coli

Bacterial diarrhoeal diseases have significant influence on global human health, and are a leading cause of preventable death in the developing world. Enterohaemorrhagic Escherichia coli (EHEC), pathogenic strains of E. coli that carry potent toxins, have been associated with a high number of large-scale outbreaks caused by contaminated food and water sources. This pathotype produces diarrhoea and haemorrhagic colitis in infected humans, and in some patients leads to the development of haemolytic uremic syndrome (HUS), which can result in mortality and chronic kidney disease. A major obstacle to the treatment of EHEC infections is the increased risk of HUS development that is associated with antibiotic treatment, and rehydration and renal support are often the only options available. New treatments designed to prevent or clear E. coli infections and reduce symptoms of illness would therefore have large public health and economic impacts. The three main aims of this thesis were: to explore mouse models for pre-clinical evaluation in vivo of small compounds that inhibit a major EHEC colonisation factor, to assess the production and role of two proteins considered promising candidates for a broad-spectrum vaccine against pathogenic E. coli, and to investigate a novel compound that has recently been identified as a potential inhibitor of EHEC toxin production. As EHEC cannot be safely tested in humans due to the risk of HUS development, appropriate small animal models are required for in vivo testing of new drugs. A number of different mouse models have been developed to replicate different features of EHEC pathogenesis, several of which we investigated with a focus on colonisation mediated by the Type III Secretion System (T3SS), a needle-like structure that translocates bacterial proteins into host cells, resulting in a tight, intimate attachment between pathogen and host, aiding colonisation of the gastrointestinal tract. As E. coli models were found not to depend significantly on the T3SS for colonisation, the Citrobacter rodentium model, a natural mouse pathogen closely related to E. coli, was deemed the most suitable mouse model currently available for in vivo testing of T3SS-targeting compounds. Two bacterial proteins, EaeH (an outer membrane adhesin) and YghJ (a putative secreted lipoprotein), highly conserved surface-associated proteins recently identified as III protective antigens against E. coli infection of mice, were explored in order to determine their suitability as candidates for a human vaccine against pathogenic E. coli. We focused on the expression and function of these proteins in the EHEC O157:H7 EDL933 strain and the adherent-invasive E. coli (AIEC) LF82 strain. Although expression of EaeH by other E. coli pathotypes has recently been shown to be upregulated upon contact with host intestinal cells, no evidence of this upregulation could be demonstrated in our strains. Additionally, while YghJ was produced by the AIEC strain, it was not secreted by bacteria under conditions that other YghJ-expressing E. coli pathotypes do, despite the AIEC strain carrying all the genes required to encode the secretion system it is associated with. While our findings indicate that a vaccine that raises antibodies against EaeH and YghJ may have limited effect on the EHEC and AIEC strains we used, recent studies into these proteins in different E. coli pathogens have suggested they are still excellent candidates for a broadly effective vaccine against E. coli. Finally, we characterised a small lead compound, identified by high-throughput screening as a possible inhibitor of Shiga toxin expression. Shiga toxin production causes both the symptoms of illness and development of HUS, and thus reduction of toxin production, release, or binding to host receptors could therefore be an effective way to treat infections and decrease the risk of HUS. Inhibition of Shiga toxin production by this compound was confirmed, and was shown to be caused by an inhibitory effect on activation of the bacterial SOS response rather than on the Shiga toxin genes themselves. The bacterial target of this compound was identified as RecA, a major regulator of the SOS response, and we hypothesise that the compound binds covalently to its target, preventing oligomerisation of RecA into an activated filament. Altogether, the results presented here provide an improved understanding of these different approaches to combating EHEC infection, which will aid the development of safe and effective vaccines and anti-virulence treatments against EHEC.

Perfil epidemiológico y análisis de la formulación antibiótica en pacientes con infección urinaria nosocomial en la Fundación Cardioinfantil en el año 2014

Introducción: La IVU es muy frecuenten en la (FCI - IC), Alrededor el 60% de los pacientes con diagnóstico de IVU nosocomial corresponden a gérmenes resistente, Desde el año 2010 el CLSI disminuyó los puntos de corte de sensibilidad en las enterobacteriaceae y removió la necesidad de tamizaje y confirmación de (BLEE), en el presente trabajo se pretende determinar el perfil epidemiológico de la formulación antibiótica en pacientes con IVU nosocomial. Diseño: Se realizó un estudio observacional analítico de corte transversal. Métodos: Se realizó un análisis univariado, bivariado y multivariado. El análisis bivariado y multivariado se realizó para determinar la medida de asociación teniendo en cuenta la formulación de Carbapenemico la variable dependiente, evaluándose mediante chi cuadrado. Resultados: Se revisaron 131 urocultivos, se incluyeron 116. Los aislamientos microbiológicos más frecuentemente encontrados fueron E. Coli y K. Pneumoniae, el 43.4% de los aislamientos, presentaron expresión de BLEE, 90% de los aislamientos fueron sensibles a Cefepime. La mayoría de los modelos obtenidos mostraron una fuerte asociación entre el reporte de BLEE en antibiograma con la formulación de carbapenémicos como terapia final OR 33,12 IC 95% (2,90 – 337,4). Conclusión: La epidemiologia de la IVU nosocomial en la FCI-IC no difiere de las referencias internacionales, no hay adherencia a las guías de manejo intrahospitalario y el reporte de la palabra BLEE en el antibiograma predice la formulación de antibiótico carbapenémico por el médico que lee el urocultivo

Impacto de los Niveles de Tacrolimus en el Rechazo al Injerto y la Tasa de Filtración Glomerular en Pacientes con Trasplante Hepático realizado en la FCI-IC entre 2009 y 2014

Introducción: El tacrolimus es el medicamento de elección para evitar el rechazo al injerto hepático. Su dosis se ajusta a partir de los niveles séricos que se toman periódicamente para asegurar rango terapéutico. Además, niveles elevados se asocian con disfunción renal postrasplante. Sin embargo, no hay consenso frente a los niveles adecuados para pacientes con trasplante hepático. Objetivo: Determinar la relación entre los niveles de tacrolimus y la presencia de rechazo agudo al injerto hepático en pacientes con trasplante hepático realizado en la Fundación Cardioinfantil – Instituto de Cardiología (FCI-IC). Determinar la relación entre los niveles de tacrolimus y la TFG en pacientes con trasplante hepático realizado en la FCI-IC. Métodos: Estudio observacional tipo cohorte histórica en pacientes adultos con trasplante hepático realizado en la FCI-IC entre 2009-2014. Resultados: No se encontró una asociación estadísticamente significativa entre los niveles de tacrolimus y la presencia de rechazo agudo, en sus diferentes definiciones (OR=1,02, p=0,14 y OR=1,01, p=0,29) incluso al ajustar por otras covariables (OR=1,03, p=0,10 y OR=1,02, p=0,25). No fue posible corroborar el diagnóstico con biopsia porque no todos la tenían. Si bien la relación entre los niveles de tacrolimus y la TFG fue estadísticamente significativa (p≤0,001), tiene bajo impacto clínico, pues la TFG disminuyó menos de un punto por cada incremento en 1 ng/ml en los niveles de tacrolimus. Conclusiones: Se necesitan más estudios para establecer la relación entre la exposición a tacrolimus y estos desenlaces para definir si es seguro disminuir su dosis con el fin de reducir los eventos adversos.

Tratamiento del rechazo mediado por anticuerpos en pacientes trasplantados renales revisión sistemática

Antecedentes: El trasplante renal es la mejor alternativa terapéutica para la enfermedad renal crónica terminal. Los medicamentos inmunosupresores previenen el rechazo. El rechazo mediado por anticuerpos es frecuente y disminuye la función y duración del injerto. Objetivo: Evaluar sistemáticamente la evidencia disponible relacionada con la eficacia y seguridad del tratamiento para el rechazo mediado por anticuerpos en pacientes trasplantados renales. Metodologia: Revisión sistemática en bases de datos MEDLINE, EMBASE, Scopus y Biblioteca virtual de la salud. Literatura gris google scholar, google academico, www.clinicaltrialsregister.eu, and https://clinicaltrials.gov/. Búsqueda manual referencias artículos pre-seleccionados así como de revisiones previamente publicadas. Se siguieron las recomendacioes guia PRISMA para la identificacion de artículos potenciales, tamizaje y selección teniendo en cuenta los criterios de inclusion. Extracción datos de acuerdo a las variables, revisión calidad de los artículos elegidos utilizando evaluación riesgo de segos de Cochrane. Resultados: Se seleccionaron 9 ensayos clínicos publicados entre 1980 y 2016, incluyeron 222 pacientes (113 brazo de intervención y 109 en el control), seguimiento promedio 16 meses. Intervenciones evaluadas plasmaféresis, inmunoadsorción y rituximab. Hubo una amplia heterogeneidad en la definición de criterios de inclusión, criterios diagnósticos de rechazo y medidas de evaluación de eficacia de las intervenciones. Tres estudios encontraron diferencias estadísticamente significativas entre los grupos de tratamiento. Conclusiones: La evidencia sobre la eficacia de los tratamientos del rechazo mediado por anticuerpos en injertos renales es de baja calidad. Son necesarios ensayos clínicos controlados para poder definir el tratamiento óptimo de estos pacientes.

Cork oak transplant: A new reality? A Physiological Approach to maximize sucess rate.

Cork oak tree (Quercus suber L.), in Portugal, is considered the national tree and have special demands and legal protection when dealing with silviculture management (pruning, debarking, thinning). Being a species of slow growth, cork oak transplanting procedures can be a valuable asset either from the economic or ecological rationales to relocate trees, re-populate areas affected by high tree mortality, increase tree density to control erosion on montado ecosystems or landscape design. This study focuses the impacts and physiological responses of ten juvenile rain fed cork oak trees (with diameter at breast height between 6 and 16cm), when subjected to transplant operations. The work was conducted in a cork oak woodland experimental plot at the campus of the University of Évora (SW Portugal), during the year of 2015. Tree’s transplants were performed with a truck-mounted hydraulic spade transplanter coupled with a proposed methodology to maximize tree survival rates, addressing techniques to limit canopy transpiration and to improve root systems prior to transplant. Tree ecophysiological indicators (sap flow, leaf water potentials and stomatal conductance) were monitored comprising the periods before and after transplant operations, and water stress avoidance practices were established to promote post-transplant tree status recovery, including irrigation to match average daily accumulated sap flow. Transplant operations were considered successful when the tree's water uptake inferred from sap flow exhibited a high correlation with solar radiation and returned to its undisturbed or pre-transplant water potential gradients in the following 2 to 3 weeks. The post-transplant tree nourishment follow up included permanent sap flow measurements and identified the time elapsed after transplantation from which the tree recovers its normal transpiration thresholds and response. Our results suggest that by following the proposed methodology the sampled cork oak trees exhibited a transplant success rate of 90%.

Multi-organ support device for combined extracorporeal carbon dioxide removal and hemofiltration treatments with pump-free solution for ultrafiltration

The use of extracorporeal organ support (ECOS) devices is increasingly widespread, to temporarily sustain or replace the functions of impaired organs in critically ill patients. Among ECOS, respiratory functions are supplied by extracorporeal life support (ECLS) therapies like extracorporeal membrane oxygenation (ECMO) and extracorporeal carbon dioxide removal (ECCO2R), and renal replacement therapies (RRT) are used to support kidney functions. However, the leading cause of mortality in critically ill patients is multi-organ dysfunction syndrome (MODS), which requires a complex therapeutic strategy where extracorporeal treatments are often integrated to pharmacological approach. Recently, the concept of multi-organ support therapy (MOST) has been introduced, and several forms of isolated ECOS devices are sequentially connected to provide simultaneous support to different organ systems. The future of critical illness goes towards the development of extracorporeal devices offering multiple organ support therapies on demand by a single hardware platform, where treatment lines can be used alternately or in conjunction. The aim of this industrial PhD project is to design and validate a device for multi-organ support, developing an auxiliary line for renal replacement therapy (hemofiltration) to be integrated on a platform for ECCO2R. The intended purpose of the ancillary line, which can be connected on demand, is to remove excess fluids by ultrafiltration and achieve volume control by the infusion of a replacement solution, as patients undergoing respiratory support are particularly prone to develop fluid overload. Furthermore, an ultrafiltration regulation system shall be developed using a powered and software-modulated pinch-valve on the effluent line of the hemofilter, proposed as an alternative to the state-of-the-art solution with peristaltic pump.

Rat Atrial Responses To Bothrops Jararacussu (jararacuçu) Snake Venom.

Envenoming by the pitviper Bothrops jararacussu produces cardiovascular alterations, including coagulopathy, systemic hemorrhage, hypotension, circulatory shock and renal failure. In this work, we examined the activity of this venom in rat isolated right atria. Incubation with venom (0.025, 0.05, 0.1 and 0.2mg/ml) caused concentration-dependent muscle contracture that was not reversed by washing. Muscle damage was seen histologically and confirmed by quantification of creatine kinase-MB (CK-MB) release. Heating and preincubation of venom with p-bromophenacyl bromide (a phospholipase A2 inhibitor) abolished the venom-induced contracture and muscle damage. In contrast, indomethacin, a non-selective inhibitor of cyclooxygenase, and verapamil, a voltage-gated Ca(2+) channel blocker, did not affect the responses to venom. Preincubation of venom with Bothrops or Bothrops/Crotalus antivenom or the addition of antivenom soon after venom attenuated the venom-induced changes in atrial function and tissue damage. These results indicate that B. jararacussu venom adversely affected rat atrial contractile activity and muscle organization through the action of venom PLA2; these venom-induced alterations were attenuated by antivenom.