Heart injury following intestinal ischemia reperfusion in rats is attenuated by association of ischemic preconditioning and adenosine

PURPOSE: To investigate the effect of ischemic preconditioning (IPC) and adenosine as strategies to protect cardiac injury caused by intestinal IR in rats, based on increasing in adenosine bioavailability and improvement of cell energy state by IPC. METHODS: Male Wistar rats were submitted to 60 minutes of intestinal ischemia and 120 minutes of reperfusion. Intravenous injections of saline or Adenosine (AD) was administered five minutes before ischemia, five minutes before reperfusion and after 55 minutes reperfusion. Cardiac samples were obtained, fixed in formalin solution, embedded in paraffin, and sections of 5 μm were stained by hematoxylin-eosin. Histological analysis of myocardium was performed according occurrence of necrosis signs: piknosis, band contraction, eosinophilic cytoplasm, karyorrhexis and vacuolization (score - zero to 5). RESULTS: The groups submitted to ischemia alone (I=4.0), and reperfusion (IR=4.5) showed highest level of lesion compared to the others (I+IPC=3.3, IR+IPC=3.6, I+AD=3.0, IR+AD=3.8). The most interesting result was association of IPC and AD in IR model (IR+IPC+AD=1.2, p=0.002), showing preservation of the heart tissue, with fibers showing typical cross-striations and nuclei characteristics. Rare and small areas of tissue necrosis was observed and suggestion of capillaries congestion. CONCLUSION: Intestinal ischemia reperfusion promotes cardiac tissue injury. Ischemic preconditioning in association with adenosine is an efficient strategy to protect the heart against ischemia and reperfusion injury. .

Receptores plaquetários P2Y12: importância na intervenção coronariana percutânea / P2Y12 platelet receptors: importance in percutaneous coronary intervention

As plaquetas estão envolvidas em vários processos biológicos, desde o combate a agentes infecciosos até a coordenação do controle da permeabilidade vascular e angiogênese. Entretanto, o seu principal foco de ação consiste na modulação da cascata de coagulação. A intervenção coronariana percutânea é um procedimento com alto risco trombogênico, que induz a ativação plaquetária e de monócitos, devido à lesão direta do endotélio e pelo contato de estruturas trombogênicas com o sangue, levando ao aumento da atividade inflamatória, tanto no local do dano vascular coronariano como de forma sistêmica. Os receptores plaquetários P2Y12 desempenham papel central na amplificação da agregação induzida por todos os agonistas plaquetários, como a adenosina difosfato, o colágeno, tromboxano A2, adrenalina e serotonina. Por esse motivo, têm sido o principal alvo das drogas antiplaquetárias. Apesar de atuarem no mesmo receptor, características farmacocinéticas e farmacodinâmicas distintas conferem peculiaridades a cada agente.

Apart from their role in hemostasis and thrombosis, platelets are involved in many other biological processes such as wound healing and angiogenesis. Percutaneous coronary intervention is a highly thrombogenic procedure inducing platelets and monocytes activation through endothelial trauma and contact activation by intravascular devices. Platelet P2Y12 receptor activation by adenosine diphosphate facilitates non-ADP agonist-mediated platelet aggregation, dense granule secretion, procoagulant activity, and the phosphorylation of several intraplatelet proteins, making it an ideal drug target. However, not all compounds that target the P2Y12 receptor have similar efficacy and safety profiles. Despite targeting the same receptor, the unique pharmacologic properties of each of these P2Y12 receptor-directed compounds can lead to very different clinical effects.

Effects of ischemic preconditioning associated to different preservation solutions in protecting the intestinal graft / Efeitos do precondicionamento isquêmico associado a diferentes soluções de preservação na proteção do enxerto intestinal

PURPOSE: To evaluate the effects of ischemic preconditioning (IPC) associate with different preservation solutions, in the protecting of gut. METHODS: Four groups of 14 rats underwent laparotomy and collecting 20 cm of ileum, for preservation, at 4ºC, in Belzer (Belz), Ringer (RL), Celsior (Cs) and Custodiol (Cust) solutions, for 24 hours. Prior to collection, half of the animals in each group were subjected to IPC. During preservation, in the periods of zero, 12, 18 and 24 hours, were conducted evaluating the degree of mucosal injury and dosage of malondialdehyde acid (MDA). RESULTS: In all periods the RL group, with and without IPC, presented MDA values higher than the Belz and Cs. The degree of mucosal injury in the non-ipc RLgroup with 12h preservation was higher than the others; with 18 and 24h, the RL and Cust had higher degrees of damage than Cs and Belz. With IPC, in all periods, the group Cs and Belz had lower degrees of injury. CONCLUSION: The Celsior and Belzer solutions had better protective effects on the gut and these effects were enhanced by IPC.

OBJETIVO: Avaliar os efeitos do precondicionamento isquêmico (PCI) associado a diferentes soluções de preservação, na proteção do intestino delgado. MÉTODOS: Quatro grupos de 14 ratos Wistar, foram submetidos à laparotomia e coleta de 20 cm de íleo, para preservação, a 4ºC, nas soluções de Belzer (Belz), Ringer (RL), Celsior (Cs) e Custodiol (Cust) por 24 horas. Previamente à coleta, em metade dos animais de cada grupo, o intestino foi submetido ao PCI. Durante a preservação, nos períodos de Zero, 12, 18 e 24 horas, foram realizados avaliação do grau de lesão da mucosa e dosagem do ácido malondialdeído (MDA). RESULTADOS: Em todos os períodos o grupo RL, sem e com pci, apresentou valores maiores de MDA do que o Belz e Cs. O grau de lesão da mucosa nos grupos sem pci com preservação de 12h, no grupo RL, foi maior que nos demais; com 18h e 24h o grupo RL e Cust apresentaram maiores graus de lesão do que Cs e Belz. Com o pci, em todos os períodos, os grupos Belz e Cs apresentaram menores graus de lesão CONCLUSÃO: As Soluções Celsior e Belzer tiveram melhores efeitos na proteção do intestino e estes efeitos foram incrementados pelo precondicionamento isquêmico.

Vasorreactividad a adenosina en los pacientes con hipertensión pulmonar arterial: prevalencia y respuesta clínica, funcional y hemodinámica al tratamiento con diltiazem / Acute vasodilatador test using adenosine in patients with pulmonary arterial hypertension: prevalence and clinical, functional and hemodynamic response after diltiazem treatment

Pulmonary arterial hypertension (PAH) is a severe and progressive disease. Invasive hemodynamic study (HS) is required to confirm the diagnosis of PAH and to perform the vasodilator test (VT) with adenosine. Vasodilator acute responders (VAR) may have a sustained benefit with diltiazem. There is not national information regarding these issues. All patients with probable PAH were evaluated with HS and VT. VAR were treated with diltiazem and followed up with functional class score (FC) and 6 minute walk test. After 6 months, a second HS was performed. Results: Between 2003 and 2008, 6/54 (11%) were VAR. All were women, 45 +/- 14 years old, 4 with idiopathic PAH, 4 in FCIII and 2 in FCII. After two years of treatment, all patients clinically improved. Walked distance significantly increased by 83 and 87 m at month 12 and 24 respectively. Hemodynamic parameters also improved. Therapy with diltiazem is effective in VAR patients supporting the convenience to perform the VT.

La Hipertensión Pulmonar Arterial (HAP) es una entidad grave y progresiva. El estudio hemodinámica (EH) permite certificar el diagnóstico y evaluar la vasorreactividad mediante adenosina. Los pacientes vaso-reactivos podrían responder a terapia con diltiazem. No existe información nacional al respecto. En nuestro programa todo paciente con sospecha de HAP es sometido a EH diagnóstico y de vasorreactividad. Los positivos son tratados con diltiazem y seguidos semestralmente según capacidad funcional (CF) y con test de caminata. Al 6º mes se efectúa un 2º EH. Entre 2003-2008, 6/54 (11%) de los pacientes con HAP fueron vasorreactivos. Todas mujeres, 45 +/- 14 años, 4 con HPA idiopática, 4 en CFIII y 2 en CFII. A los 2 años, todos mejoraron clínicamente. La distancia recorrida aumentó significativamente en los meses 12 y 24 en 83 y 87 m respectivamente. Todas las variables hemodinámicas mejoraron. La terapia con diltiazem es efectiva en los pacientes vaso-reactivos lo que justifica usar el test de vasorreactividad.

Effects of adenosine on the organ injury and dysfunction caused by hemorrhagic shock

Adenosine has been shown in animal and human studies to decrease the post-ischemic myocardial injury by lowering the levels of tumor necrosis factor-a. The objectives of the study was to examine the protective effects of adenosine on the organ injury [liver, kidney, pancreas] associated with hemorrhagic shock in rats. The study was conducted at Cardiovascular Physiology laboratory, King Saud University, Riyadh in 2007-2008. Anesthetized male Sprague- Dawley rats were assigned to hemorrhage and resuscitation treated with 20mM adenosine, untreated, or similar time matched control groups [n=6 per group]. Rats were hemorrhaged for one hour using a reservoir model. Arterial blood pressure was monitored for one hour, and maintained at a mean arterial blood pressure of 40 mmHg. Adenosine 20mM was injected intra-arterially, before resuscitation in the adenosine treated group. Resuscitation was performed by reinfusion of the sheded blood for 30 minutes. Arterial blood samples were analyzed for biochemical indicators of multiple organ injury: 1] liver function: aspartate aminotransferase [AST], alanine aminotransferase [ALT], 2] renal function: urea and creatinine, 3] pancreatic function: amylase. In the control group there was no significant rise in the serum levels of [i] urea and creatinine, [ii] aspartate aminotransferase [AST] and alanine aminotransferase [ALT], [iii] amylase. While in the adenosine treated group, resuscitation from one hour of hemorrhagic shock resulted in significant rises in the serum levels of [i] urea and creatinine, [ii] aspartate aminotransferase [AST] and alanine aminotransferase [ALT], [iii] amylase. Treatment of rats with 20mM adenosine before resuscitation following one hour of hemorrhagic shock decreased the multiple organ injury and dysfunction caused by hemorrhagic shock. Adenosine attenuated the renal, liver and pancreatic injury caused by hemorrhagic shock and resuscitation in rats. Thus, the inflammatory response to shock may contribute to the multiple organ failure developed after hemorrhagic shock and resuscitation

Endothelial and non-endothelial coronary blood flow reserve and left ventricular dysfunction in systemic hypertension

OBJECTIVES: We evaluated the impairment of endothelium-dependent and endothelium-independent coronary blood flow reserve after administration of intracoronary acetylcholine and adenosine, and its association with hypertensive cardiac disease. INTRODUCTION: Coronary blood flow reserve reduction has been proposed as a mechanism for the progression of compensated left ventricular hypertrophy to ventricular dysfunction. METHODS: Eighteen hypertensive patients with normal epicardial coronary arteries on angiography were divided into two groups according to left ventricular fractional shortening (FS). Group 1 (FS >0.25): n=8, FS=0.29 ± 0.03; Group 2 (FS <0.25): n=10, FS= 0.17 ± 0.03. RESULTS: Baseline coronary blood flow was similar in both groups (Group 1: 80.15 ± 26.41 mL/min, Group 2: 100.09 ± 21.51 mL/min, p=NS). In response to adenosine, coronary blood flow increased to 265.1 ± 100.2 mL/min in Group 1 and to 300.8 ± 113.6 mL/min (p <0.05) in Group 2. Endothelium-independent coronary blood flow reserve was similar in both groups (Group 1: 3.31 ± 0.68 and Group 2: 2.97 ± 0.80, p=NS). In response to acetylcholine, coronary blood flow increased to 156.08 ± 36.79 mL/min in Group 1 and to 177.8 ± 83.6 mL/min in Group 2 (p <0.05). Endothelium-dependent coronary blood flow reserve was similar in the two groups (Group 1: 2.08 ± 0.74 and group Group 2: 1.76 ± 0.61, p=NS). Peak acetylcholine/peak adenosine coronary blood flow response (Group 1: 0.65 ± 0.27 and Group 2: 0.60 ± 0.17) and minimal coronary vascular resistance (Group 1: 0.48 ± 0.21 mmHg/mL/min and Group 2: 0.34 ± 0.12 mmHg/mL/min) were similar in both groups (p= NS). Casual diastolic blood pressure and end-systolic left ventricular stress were independently associated with FS. CONCLUSIONS: In our hypertensive patients, endothelium-dependent and endothelium-independent coronary blood flow reserve vasodilator administrations had similar effects in patients with either normal or decreased ...

Lead acetate induced contraction in rat tracheal smooth muscle is independent of epithelium.

Airways are the primary target of lead exposure from atmospheric pollution, its effect on airway smooth muscle and their responsiveness to bronchoactive agents is not clearly understood. In the present investigation the effect of lead on the isolated airway smooth muscle activity was studied in organ bath set-up. Further the involvement of airway epithelium was examined and the responsiveness of airway smooth muscle to adenosine, acetylcholine (bronchoconstrictors) and isoproterenol (bronchodilator) was also investigated. Lead in concentration of 10(-12) M to 10(-4) M produced concentration-dependant contractile response in rat tracheal rings. Acetylcholine and adenosine induced concentration-dependent contractile response was slightly inhibited after lead exposure. The relaxant response to isoproterenol was also inhibited in lead exposed tissues. Epithelium removal did not significantly change the contractile response to lead suggesting that the lead induced contraction of airway smooth muscle is epithelium independent.

Adenosine A1 receptor-mediated inhibition of in vitro prolactin secretion from the rat anterior pituitary

In previous studies, we demonstrated biphasic purinergic effects on prolactin (PRL) secretion stimulated by an adenosine A2 agonist. In the present study, we investigated the role of the activation of adenosine A1 receptors by (R)-N6-(2-phenylisopropyl)adenosine (R-PIA) at the pituitary level in in vitro PRL secretion. Hemipituitaries (one per cuvette in five replicates) from adult male rats were incubated. Administration of R-PIA (0.001, 0.01, 0.1, 1, and 10 æM) induced a reduction of PRL secretion into the medium in a U-shaped dose-response curve. The maximal reduction was obtained with 0.1 æM R-PIA (mean ± SEM, 36.01 ± 5.53 ng/mg tissue weight (t.w.)) treatment compared to control (264.56 ± 15.46 ng/mg t.w.). R-PIA inhibition (0.01 æM = 141.97 ± 15.79 vs control = 244.77 ± 13.79 ng/mg t.w.) of PRL release was blocked by 1 æM cyclopentyltheophylline, a specific A1 receptor antagonist (1 æM = 212.360 ± 26.560 ng/mg t.w.), whereas cyclopentyltheophylline alone (0.01, 0.1, 1 æM) had no effect. R-PIA (0.001, 0.01, 0.1, 1 æM) produced inhibition of PRL secretion stimulated by both phospholipase C (0.5 IU/mL; 977.44 ± 76.17 ng/mg t.w.) and dibutyryl cAMP (1 mM; 415.93 ± 37.66 ng/mg t.w.) with nadir established at the dose of 0.1 æM (225.55 ± 71.42 and 201.9 ± 19.08 ng/mg t.w., respectively). Similarly, R-PIA (0.01 æM) decreased (242.00 ± 24.00 ng/mg t.w.) the PRL secretion stimulated by cholera toxin (0.5 mg/mL; 1050.00 ± 70.00 ng/mg t.w.). In contrast, R-PIA had no effect (468.00 ± 34.00 ng/mg t.w.) on PRL secretion stimulation by pertussis toxin (0.5 mg/mL; 430.00 ± 26.00 ng/mg t.w.). These results suggest that inhibition of PRL secretion after A1 receptor activation by R-PIA is mediated by a Gi protein-dependent mechanism.

Effect of some adenosine compounds on smooth muscles of the sheep bladder Osteius ovis L.

Purines have widespread and specific extracellular signalling actions in the regulation of a variety of functions in many tissues of both invertebrates and vertebrates. The effect of some adenosine compound on sheep bladder smooth muscle contraction induced by KCI and ACh was investigated invitro. Preparations were prepreated with adenosine or ATP befor agonist exposure. It was found that adenosine inhibited K- induced contracture and enhanced Ach-induced contracture. These actions were blocked by P[1] antagonist theophylline. The results also show that ATP potentiated both KCI and ACh induced contracture. Theses actions antagonized by P[2] receptor antagonist Quinidine. These results suggest that blader smoth muscle may have A[1], A[2] and P[2x] receptors

Influence of influenza viral infection on airway smooth muscle activity.

The contractility of airway smooth muscle (ASM) plays an important role in pathophysiology of several bronchial disorders. Increased contraction of ASM during asthma and respiratory viral infection has been attributed to the release of mediators acting through different receptors. In the present study, influence of influenza type A virus (H1N1) infection has been examined on ASM responsiveness to various bronchoactive agents e.g. adenosine, histamine, 5-hydroxytryptamine (5-HT) and isoproterenol in an organ bath set up for isolated tissue preparation. The contractile effect of adenosine, histamine and 5-HT was enhanced, however, relaxant response of isoproterenol was attenuated with the duration following viral exposure. The most prominent response was observed 48 to 72 hr after infection and tissues from multiple exposure to virus infected animals showed the maximum contractile response. Results demonstrated the deleterious effect of viral infection on ASM function and the findings will be helpful in understanding the mechanism of influenza virus induced bronchoconstriction.

La activación de los receptores A1 de adenosina atenua el atontamiento de miocardio en el conejo / The activation of A1 adenosine receptors attenuates myocardial stunning in the rabbit

Los corazones expuestos a un período prolongado de isquemia (ü 30 minutos) presentan un menor tamaño de infarto cuando son reperfundidos en presencia de adenosina. Sin embargo, cuando el período de isquemia es menor, estas áreas de infarto son poco significativas, quedando en forma transitoria un cuadro de disfunción ventricular postisquémica. El objetivo del presente trabajo fue determinar el efecto de la adenosina, (administrada solamente en la reperfusión) sobre las alteraciones sistólicas y diastólicas presentes en la disfunción ventricular postisquémica así como también determinar sí en dicho efecto están involucrados los receptores A1. Corazones aislados e isovolúmicos de conejo, fueron sometidos a isquemia global de 15 minutos y reperfusión de 30 minutos. Durante la reperfusión se evaluó la función ventricular. En el grupo control, la presión desarrollada (PDVI) se recuperó hasta un 56ñ2% a los 30 minutos de la reperfusión, mientras que con la administración de adenosina alcanza un 75ñ3% (P<0.05 vs. control) Sin embargo, cuando se administró la adenosina junto con el bloqueante selectivo del receptor A1 (DPCPX) la PDVI alcanzó un 50ñ2% (P<0.05 vs. control). La presión diastólica final (PDFVI) (rigidez diastólica) en el grupo control, aumentó un 293ñ4%, a los 30 minutos de la reperfusión, mientras que con la administración de adenosina, la PDFVI alcanzó un 15ñ8% (P<0.05 vs. control). La reperfusión en presencia de adenosina más DPCPX no logró atenuar el aumento de la rigidez diastólica, alcanzando un 493ñ9 % (P<0.05 vs. control). La adenosina atenuó las alteraciones sistólicas y la rigidez diastólica de la disfunción postisquémica. Este efecto protector fue abolido por el bloqueante de los receptores A1, sugiriendo un rol de estos receptores en la protección inducida por adenosina

Modelo de hipofuncao adenossinergica para esquizofrenia: interacao entre os sistemas purinergico, glutamatergico e dopaminergico / Model of adenosinergic hypofunction for schizophrenia: interactions between purinergic, glutamatergic and dopaminergic systems

Os modelos fisiopatologicos da esquizofrenia classicamente tem abordado diversos neurotransmissores, como a dopamina, a serotonina e o glutamato. Neste trabalho, propomos que alteracoes envolvendo o sistema purinergico...

Possible involvement of A1 receptors in the inhibition of gonadotropin secretion induced by adenosine in rat hemipituitaries in vitro

We investigated the participation of A1 or A2 receptors in the gonadotrope and their role in the regulation of LH and FSH secretion in adult rat hemipituitary preparations, using adenosine analogues. A dose-dependent inhibition of LH and FSH secretion was observed after the administration of graded doses of the R-isomer of phenylisopropyladenosine (R-PIA; 1 nM, 10 nM, 100 nM, 1 µM and 10 µM). The effect of R-PIA (10 nM) was blocked by the addition of 8-cyclopentyltheophylline (CPT), a selective A1 adenosine receptor antagonist, at the dose of 1 µM. The addition of an A2 receptor-specific agonist, 5-N-methylcarboxamidoadenosine (MECA), at the doses of 1 nM to 1 µM had no significant effect on LH or FSH secretion, suggesting the absence of this receptor subtype in the gonadotrope. However, a sharp inhibition of the basal secretion of these gonadotropins was observed after the administration of 10 µM MECA. This effect mimicked the inhibition induced by R-PIA, supporting the hypothesis of the presence of A1 receptors in the gonadotrope. R-PIA (1 nM to 1 µM) also inhibited the secretion of LH and FSH induced by phospholipase C (0.5 IU/ml) in a dose-dependent manner. These results suggest the presence of A1 receptors and the absence of A2 receptors in the gonadotrope. It is possible that the inhibition of LH and FSH secretion resulting from the activation of A1 receptors may have occurred independently of the increase in membrane phosphoinositide synthesis

Purification and characterization of a type II phosphatidylinositol 4-kinase from rat spleen and comparison with a PtdIns 4-kinase from lymphocytes.

A PtdIns 4-kinase from rat spleen particulate fraction was purified to homogeneity and its molecular properties were compared with a PtdIns 4-kinase from splenic lymphocytes. The enzyme activity was solubilized from spleen particulate fraction with Triton X-100 and chromatographed sequentially on phosphocellulose, DEAE-sephacel, heparin acrylamide and hydroxyapatite columns. The purified enzyme preparation showed a 55 kDa band on SDS-PAGE with silver staining. Renaturation of the enzyme activity from SDS-PAGE showed that it comigrated with the 55 kDa protein. Characterization of the enzyme showed that it was a type II PtdIns 4-kinase. Polyclonal antibodies raised against PtdIns 4-kinase inhibited the enzyme activity in in vitro assays. Analysis of adult rat tissue particulate fractions on immunoblots showed restricted immunoreactivity among PtdIns 4-kinases. However, the immunoreactivity is conserved in lymphoid tissues from mouse to human, suggesting that lymphoid tissue has a distinct PtdIns 4-kinase. Activation of rat splenocytes with Con A showed two fold increase in PtdIns 4-kinase activity. Comparison of PtdIns 4-kinases from spleen and splenic lymphocytes showed identical chromatographic behaviour, molecular mass, immunoreactivity, K(m) values for PtdIns and inhibition by adenosine.

Adenosina exógena y disfunción postisquémica en el corazón aislado de conejo / Exogenous adenosine and postischemic dysfunction in the isolated rabbit heart

Es conocido que la adenosina atenúa las alteraciones sistólicas de la disfunción ventricular postisquémica ("miocardio atontado"), pero poco se conoce acerca de los efectos de este compuesto sobre las alteraciones diastólicas y, por otra parte, existe controversia sobre la importancia del momento de su administración. El objetivo del presente trabajo fue determinar los efectos de la adenosina cuando es administrada: a) desde antes de la isquemia y b) a partir del inicio de la reperfusión, sobre la función sistólica y diastólica del "miocardio atontado". Un objetivo adicional fue determinar se la adenosina modifica la liberación de creatinfosfokinasa (CPK) y lacticodeshidrogenasa (LDH) que ocurre en el "miocardio atontado". Se utilizaron corazones aislados isovolúmicos de conejo, perfundidos según la técnica modificada de Langendorff, y sometidos a isquemia global de 15 minutos y reperfusión de 30 minutos. La colocación de un balón de látex en el ventrículo izquierdo, conectado a un transductor de presión, permitió registrar la presión intraventricular izquierda, su primera derivada (dP/dt) y la presión de perfusión coronaria (PP). Se midieron, la presión diastólica final (rigidez diastólica), la PP y la máxima velocidad de ascenso y de descenso de la presión (+dP/dtmáx y -dP/dtmáx, respectivamente). Se calculó la presión desarrollada de ventrículo isquierdo, el cociente entre la +dP/dtmáx y dP/dtmáx (+P/-P) y la constante de tiempo de decaimiento de la presión ventricular durante la fase de relajación isovolúmica (t, Tau). La adenosina, adminstrada tanto antes del período de isquemia como al comienzo de la reperfusión, atenuó las alteraciones sistólicas y la rigidez diastólica sin modificar la relajación isovolúmica. Asimismo, la adenosina no modificó significativamente la liberación de CPK y LDH.

Papel de la adenosina sobre la acción antiarrítmica de los digitálicos / Role of adenosine on the antiarrhythmic action of digitalis

La acción de la adenosina sobre el periodo refractario funcional de los tejidos auriculares y en la cancelación del flutter auricular, es semejante a la de los digitálicos. Tal hecho sugiere la posible existencia de una participación adenílica en la acción digitálica. Por ello medimos las concentraciones plasmáticas de adenosina al infundir ouabaína, e investigamos el efecto del digitálico sobre el periodo refractario de tejidos auriculares y sobre el flutter en condiciones de inhibición colinérgico y bloqueo purinérgico. En perros, se administró ouabaína hasta inducir fibrilación ventricular. Se obtuvo sangre del seno coronario y de la vena femoral, midiendo la adenosina por cromatagrafía de líquidos. El periodo refractario se midió con la ténica del estímulo extra acoplado. El flutter se indujo al estimular el haz internodal posterior. Los resultados muestran que la concentración de adenosina se elevó más de 100 por ciento en plama de seno coronario; el efecto de la ouabaína sobre el periodo refractario no se modificó con la inhibición colinérgica, pero sí fue inhibido por aminofilina; el digitálico modificó su acción en la cancelación del flutter en presencia de aminofilina. Conclusión: en la acción antiarrítmica de los digitálicos parece participar un componente adenílico que resulta de la liberación de adenosina del corazón

Inhibitory effects of Diazepam in rat Vas Deferens: role of Calcium

Diazepam and Ro5-4864 effects on noradrenaline-induced rat vas deferend contractions were studied. We investigated whether central or peripheral type benzodiazepine receptors were involved, by studying the effects of the selective central or peripheral benzodiazepine receptor antagonists, flumazenil (Ro 151788) or PK 11195 respectively. Diazepam interactions with GABA, adenosine, theophylline, and hypercalcic medium (3.5mM) were studied. Also, we investigate diazepam effect on KC1 depolarized vas deferens. Results showed that diazepam (10(-4) to 1.7x10(-4) M)) and Ro 5-4864 (10(-5) to 5.5x10(-5)M) inhibited NA-induced vas deferens contractions and that neither flumazenil nor PK 11195 antagonized diazepam or Ro 5-4864 inhibitory effects respectively. GABA, adenosine and theophylline did not modify neither NA vas deferens response nor diazepam inhibitory action. Diazepam effect was significantly reduced in an 3.5 mM calcium medium and KC1 vas deferense was inhibited by diazepam 1.3x10(-5) and 1.3 x 10(-4) M. It is concluded that in rat vas deferens diazepam effect seems to be related with calcium mobilization.

Uso de la adenosina en la taquicardia paroxística supraventricular / Use of adenosine in paroxysmal supraventricular tachycardia

Los autores presentan cuatro casos de pacientes ingresados al Centro de Cuidados Intensivos del Hospital Central de las Fuerzas Armadas, con diagnóstico de taquicardia paroxística supraventricular. En todos los casos se les realizó maniobras vagales, las que fueron inefectivas para yugular dicha arritmia; a un paciente se le realizó verapamil sin éxito. Todos fueron tratados con adenosina, lográndose excelente respuesta terapéutica, no constatándose efectos secundarios en la utilización de dicho fármaco. Si bien el número de casos no es significativo, se plantea el uso de dicho fármaco en la taquicardia paroxística supraventricular en la cual el nodo aurículo ventricular forma parte del circuito de dicha arritmia.Se realiza una revisión bibliográfica de dicho fármaco, planteándose un protocolo para su utilización