Early preconditioning protection against stunning in conscious sheep. Role of KATP channels.

The aim of this study was to assess early preconditioning protection against stunning in conscious sheep and analyze the role of ATP-dependent potassium (KATP) channels in the protective mechanism. Chronically instrumented animals were submitted to a 12 min reversible ischemia and 2 h reperfusion. Early preconditioning, consisting of six 5 min occlusion-5 min reperfusion periods, followed by 45 min normoperfusion before the prolonged ischemia protected against stunning (P < 0.01). In these experimental conditions, current agents used to analyze sarcolemmal (sKATP) and mitochondrial (mKATP) KATP channels could not clearly establish their participation in the protective mechanism. At doses that inhibit sKATP channels they were unable to block preconditioning protection against stunning (glibenclamide) or conversely, blocked preconditioning at doses that do not inhibit these channels (HMR1098). Moreover, both mKATP channel agonists (diazoxide) and antagonists (5HD) protected against stunning, a response that could be due to their effect via an alternative mitochondrial pathway.

Expression of the MDR-1 gene-encoded P-glycoprotein in cardiomyocytes of conscious sheep undergoing acute myocardial ischemia followed by reperfusion.

We have recently reported that in chronic myocardial ischemia, adult mammalian cardiomyocytes express P-glycoprotein (P-gp). We now investigate if P-gp is also expressed in acute regional ischemia followed by reperfusion. Adult conscious sheep underwent 12-min occlusion of the mid-left anterior descending artery (inflatable cuff). Successful ischemia-reperfusion was confirmed by monitoring percent systolic left ventricular anterior wall thickening (sonomicrometry) during the whole ischemic period and every 10 min over 2 hr following cuff deflation. At 3, 24, and 48 hr after reperfusion, P-gp expression was investigated by immunohistochemistry and Western blot and MDR-1 mRNA by RT-PCR. Cardiomyocytes in the occluded artery territory (but not those in remote areas) consistently expressed P-gp at their sarcolemma. Whereas at 3 and 24 hr P-gp was mainly observed in the T tubules, at 48 hr it predominated in intercalated discs and gap junctions. RT-PCR and Western blot revealed higher expression in ischemic than in control myocardium. We conclude that in adult sheep with acute myocardial ischemia, the MDR-1 gene-encoded P-gp is expressed at the sarcolemma of the cardiomyocytes from 3 hr up to at least 48 hr after reperfusion.

Role of the cyclooxygenase pathway in the protection against postischemic stunning in conscious sheep.

OBJECTIVE: There are controversial reports in conscious animals regarding the role of cyclooxygenase-2 in late preconditioning (LP). This study analyzed the effect of COX-2 involvement in non-preconditioned hearts (NP) and in mediation of LP protection against stunning in conscious sheep submitted to a prolonged reversible ischemia. METHODS: Six groups were considered: NP: 12 min ischemia and 120 min reperfusion; LP consisting of six periods of 5 min-ischemia-5 min reperfusion 24 h before the 12 min ischemia; NP and LP with either the non-selective COX-1 and COX-2 inhibitor, aspirin (20 mg/kg), or the specific COX-2 inhibitor, celecoxib (3 mg/kg) before the 12 min ischemic period. RESULTS: Mean postischemic wall thickening fraction (as % of preischemic values) improved from 49.6 +/- 4.0% in NP to 72.5 +/- 3.5% in LP (p < 0.01) and a similar protection was obtained with aspirin and celecoxib in NP hearts (p < 0.01). Neither aspirin nor celecoxib administration prior to the prolonged ischemia on day 2 abrogated LP improvement of postischemic dysfunction. Moreover, LP with aspirin improved the protective response (80.7 +/- 2.6%) over that obtained with aspirin in NP hearts (66.6 +/- 4.7%, p < 0.05). This effect was not obtained with celecoxib. CONCLUSIONS: Aspirin and celecoxib showed that COX-2 has a detrimental effect on mechanical cardioprotection in NP hearts of conscious sheep submitted to a prolonged reversible ischemia, and does not seem to participate as mediator of LP. Aspirin revealed a similar COX-1 deleterious action, since only when both COX-1 and COX-2 were inhibited, LP was put in evidence adding functional improvement over that obtained in NP hearts treated with aspirin.

Effects of short-term inhaled nitric oxide on interleukin-8 release after single-lung transplantation in pigs.

BACKGROUND: Lung transplantation has evolved to become an effective treatment for a variety of end-stage lung diseases. However, severe reperfusion injury is still a major cause for postoperative morbidity and mortality. Although lung reperfusion injury is complex and has not been fully comprehended yet, neutrophil infiltration and cytokine activation have been postulated to play a main role. Recent studies showed that nitric oxide (NO) therapy has salutary effects on lung chronic and acute pathologies because it inhibits interleukin-8 (IL-8) release, but no data have been found on its effects during organ harvest. The aim of this study was to assess whether low doses of inhaled NO pre-treatment at the time of harvesting improves allograft function during early reperfusion in a porcine model. METHODS: Twenty-two Landrace pigs were randomly assigned to NO-treated and control groups. In NO-treated pigs, NO at 20 ppm was administered 30 min before harvest. During the early allograft reperfusion period IL-8 content, dynamic and static compliance and gas exchange (Pa/FiO2 and PaO2) were measured in both control and NO-treated lungs. RESULTS: Pre-treatment with NO at the time of harvesting showed improvement of allograft function in terms of dynamic (92 +/- 8% in NO vs 72 +/- 7% in the control group, p < .05) and static (83 +/- 8% in NO vs 63 +/- 7% in the control group, p < 0.05) compliance and gas exchange (PaO2: 96 +/- 4% in NO vs 74 +/- 4.5% in the control group, p < 0.01; Pa/FiO2: 97 +/- 5% in NO vs 74 +/- 5% in the control group, p < 0.01) by diminishing IL-8 (66.5 +/- 4.7 pg/ml in NO versus 208 +/- 43 pg/ml in the control group, p < 0.05) release in pigs. CONCLUSION: These results show for the first time that NO pre-treatment at the time of harvesting reduces allograft reperfusion injury in part due to its effects on IL-8 release.

[Effect of different doses of aspirin on preconditioning against stunning in conscious sheep]. / Efecto de diferentes dosis de aspirina sobre el precondicionamiento contra el atontamiento en ovejas.

UNLABELLED: Non-steroid antiinflammatory drugs, inhibitors of cyclooxigenase (COX), have been postulated to have deletereous effects on the heart. Recently, COX-2 inhibitors have also been found to block late preconditioning (LP) protection. Aspirin is the most widely clinically used non-steroid antiinflammatory drug; yet its effect on LP in big mammals has not been determined. It inhibits the two cyclooxigenase isoenzymes (COX-1 and COX-2), at high doses being used as an antiinflammatory drug and at low doses as an antithrombotic agent. The goal of this study was thus, to analyse the effect of different aspirin doses on LP protection against stunning and arrhythmias in a conscious sheep model. The animals were divided in 5 groups: control (C): 12 min ischemia (I)-2 hr reperfusion (R); LP: 6 periods of 5 min I-5 min R, 24 hr before 12 min I, and three groups same as LP, but with 1.5 (LPA1.5), 8 (LPA8) and 20 (LPA20) mg/kg aspirin respectively, administered 10 min before the first preconditioning I. Results showed that the antiinflammatory dose of aspirin (20 mg/kg) was able to inhibit LP against stunning (C vs LPA20, NS), whereas low (1.5 mg/kg) and intermediate (8 mg/kg) doses did not interfere with the protection (C vs LP, LPA1.5 and LPA8, p < 0.01). Moreover, no dose altered the protection against arrhythmias. CONCLUSION: Antithrombotic aspirin doses would not inhibit LP protection against stunning, whereas high antiinflammatory doses would be potentially deletereous. Since high doses of aspirin blocked LP when administered before the triggering episodes, our results show that the COX pathway might be involved as a trigger of LP against stunning.

Acción protectora de la nitroglicerina en el precondicionamiento tardío contra las arritmias / Protective function of nitroglycerin in late myocardial preconditioning against arrhythmias

In this reportthe protective function of nitroglycerin in late myocardial preconditioning against arrhytmias is considered. The results obtained in this study demonstrte thar the reatment with nitroglycerin instead of the preconditioning periods decreases the incidence of arrhythmic episodes similary to the late preconditioning. This is the first report that proves that the late preconditioning against arrhythmias can mimetize pharmacologically with supply of a giver of nitric oxide

Efecto de diferentes dosis de asoirina sobre el precondocionamiento contra el atontamiento en ovejas / Effect of different doses of aspirin on preconditioning against stunning in conscious sheep

Se ha postulado que los antiinflamatorios no esteroides que actuan inhibiendo la ciclooxigenasa (COX) podrían tener efectos nocivos sobre el corazón. Recientemente se ha demostrado que los inhibidores de la COX-2 bloquean la protección por precondicionamiento tardío (PT). Se desconoce sin embargo, el efecto que pudiera tener la aspirina, el antiinflamatorio no esteroide más ampliamente utilizado en la clínica, sobre el PT en mamíferos grandes. La aspirina actúa inhibiendo las dos isoenzimas de la ciclooxigenasa (COX-1 y COX-2), siendo empleada en dosis altas como droga antiinflamatoria y en dosis bajas como agente antitrombótico.El propósito de este estudio fue analizar qué efecto tienen distintas dosis de aspirina sobre la protección delPT contra el atontamiento y las arritmias en ovejas conscientes. Se consideraron 5 grupos; control (C): 12 minde isquemia (I) y 2 hr de reperfusión (R); PT: 6 períodos de 5 min I-5 min R, 24 hr antes de la I de 12 min, ytres grupos igual que PT, pero con 1.5 (PTA1.5), 8 (PTA8) y 20 (PTA20) mg/kg de aspirina respectivamente, administrados 10 min antes de la primera I de precondicionamiento. Los resultados demostraron que la dosis antiinflamatoria de aspirina (20 mg/kg) fue capaz de inhibir el PT contra el atontamiento (C vs PTA20, NS),mientras que las dosis bajas (1.5 mg/kg) e intermedia (8 mg/kg) no afectaron la protección (C vs PT, PT1.5 yPT8, p<0.01). Asimismo, ninguna de las tres dosis alteró la protección contra las arritmias. Conclusión: Lasdosis antiagregantes plaquetarias de aspirina no producirían riesgo de inhibir la protección contra el atontamiento por PT, mientras que dosis antiinflamatorias elevadas serían perjudiciales. Como la aspirina se administró antes de los períodos precondicionantes, la inhibición de la cardioprotección sugiere que la COX actúacomo mecanismo gatillador del PT contra el atontamiento.

Efecto de diferentes dosis de asoirina sobre el precondocionamiento contra el atontamiento en ovejas / Effect of different doses of aspirin on preconditioning against stunning in conscious sheep

Se ha postulado que los antiinflamatorios no esteroides que actuan inhibiendo la ciclooxigenasa (COX) podrían tener efectos nocivos sobre el corazón. Recientemente se ha demostrado que los inhibidores de la COX-2 bloquean la protección por precondicionamiento tardío (PT). Se desconoce sin embargo, el efecto que pudiera tener la aspirina, el antiinflamatorio no esteroide más ampliamente utilizado en la clínica, sobre el PT en mamíferos grandes. La aspirina actúa inhibiendo las dos isoenzimas de la ciclooxigenasa (COX-1 y COX-2), siendo empleada en dosis altas como droga antiinflamatoria y en dosis bajas como agente antitrombótico.El propósito de este estudio fue analizar qué efecto tienen distintas dosis de aspirina sobre la protección delPT contra el atontamiento y las arritmias en ovejas conscientes. Se consideraron 5 grupos; control (C): 12 minde isquemia (I) y 2 hr de reperfusión (R); PT: 6 períodos de 5 min I-5 min R, 24 hr antes de la I de 12 min, ytres grupos igual que PT, pero con 1.5 (PTA1.5), 8 (PTA8) y 20 (PTA20) mg/kg de aspirina respectivamente, administrados 10 min antes de la primera I de precondicionamiento. Los resultados demostraron que la dosis antiinflamatoria de aspirina (20 mg/kg) fue capaz de inhibir el PT contra el atontamiento (C vs PTA20, NS),mientras que las dosis bajas (1.5 mg/kg) e intermedia (8 mg/kg) no afectaron la protección (C vs PT, PT1.5 yPT8, p<0.01). Asimismo, ninguna de las tres dosis alteró la protección contra las arritmias. Conclusión: Lasdosis antiagregantes plaquetarias de aspirina no producirían riesgo de inhibir la protección contra el atontamiento por PT, mientras que dosis antiinflamatorias elevadas serían perjudiciales. Como la aspirina se administró antes de los períodos precondicionantes, la inhibición de la cardioprotección sugiere que la COX actúacomo mecanismo gatillador del PT contra el atontamiento.(AU)

Acción protectora de la nitroglicerina en el precondicionamiento tardío contra las arritmias / Protective function of nitroglycerin in late myocardial preconditioning against arrhythmias

In this reportthe protective function of nitroglycerin in late myocardial preconditioning against arrhytmias is considered. The results obtained in this study demonstrte thar the reatment with nitroglycerin instead of the preconditioning periods decreases the incidence of arrhythmic episodes similary to the late preconditioning. This is the first report that proves that the late preconditioning against arrhythmias can mimetize pharmacologically with supply of a giver of nitric oxide

Efecto de diferentes dosis de aspirina sobre el precondicionamiento contra el atontamiento en ovejas. / [Effect of different doses of aspirin on preconditioning against stunning in conscious sheep]

Non-steroid antiinflammatory drugs, inhibitors of cyclooxigenase (COX), have been postulated to have deletereous effects on the heart. Recently, COX-2 inhibitors have also been found to block late preconditioning (LP) protection. Aspirin is the most widely clinically used non-steroid antiinflammatory drug; yet its effect on LP in big mammals has not been determined. It inhibits the two cyclooxigenase isoenzymes (COX-1 and COX-2), at high doses being used as an antiinflammatory drug and at low doses as an antithrombotic agent. The goal of this study was thus, to analyse the effect of different aspirin doses on LP protection against stunning and arrhythmias in a conscious sheep model. The animals were divided in 5 groups: control (C): 12 min ischemia (I)-2 hr reperfusion (R); LP: 6 periods of 5 min I-5 min R, 24 hr before 12 min I, and three groups same as LP, but with 1.5 (LPA1.5), 8 (LPA8) and 20 (LPA20) mg/kg aspirin respectively, administered 10 min before the first preconditioning I. Results showed that the antiinflammatory dose of aspirin (20 mg/kg) was able to inhibit LP against stunning (C vs LPA20, NS), whereas low (1.5 mg/kg) and intermediate (8 mg/kg) doses did not interfere with the protection (C vs LP, LPA1.5 and LPA8, p < 0.01). Moreover, no dose altered the protection against arrhythmias. CONCLUSION: Antithrombotic aspirin doses would not inhibit LP protection against stunning, whereas high antiinflammatory doses would be potentially deletereous. Since high doses of aspirin blocked LP when administered before the triggering episodes, our results show that the COX pathway might be involved as a trigger of LP against stunning.

Absence of ischemic preconditioning protection in diabetic sheep hearts: role of sarcolemmal KATP channel dysfunction.

Sarcolemmal ATP-sensitive potassium (KATP) channels have been mentioned to participate in preconditioning protection. Since these channels are altered in diabetes, it would be possible that preconditioning does not develop in diabetic (D) hearts. The purpose of this study was to assess whether early (EP) and late (LP) ischemic preconditioning protect diabetic hearts against stunning in a conscious diabetic sheep model and whether diabetes might have altered KATP channel functioning. Sheep received alloxan monohydrate (1 g) and were ascribed to three experimental groups: control (DC, 12 min of ischemia (I) followed by 2 h of reperfusion (R)), early preconditioning (DEP, six 5 min I-5 min R periods were performed before the 12 min I) and late preconditioning (DLP, same as DEP except that the preconditioning stimulus was performed 24 h before the 12 min I). Regional mechanics during reperfusion was evaluated as the percent recovery of wall thickening fraction (%WTH) expressed as percentage of basal values (100%) and KATP behaviour was indirectly assessed by monophasic action potential duration (MAPD) and sensitivity to glibenclamide blockade (0.1 and 0.4 mg/Kg). The results were compared to those obtained in normal (N) sheep. EP and LP protected against stunning in normal sheep (%WTH: NC = 63 +/- 3.7, NLP = 80 +/- 5**, NEP = 78 +/- 3*, *p < 0.05 and **p < 0.01 against NC) whereas contrary results occurred in diabetic ones, where DLP (%WTH = 60 +/- 4) afforded a similar recovery to DC (%WTH = 54 +/- 5) and DEP surprisingly worsened instead of improving mechanical function (%WTH = 38 +/- 6, p < 0.01 against DC). KATP channel behaviour appeared altered in diabetic hearts as shown by MAPD during ischemia in normal sheep (153 +/- 9 msec) compared to diabetic ones (128 +/- 11 msec, p < 0.05) and by the sensitivity to glibenclamide (while 0.4 mg/Kg blocked action potential shortening in normal and diabetic animals, 0.1 mg/Kg completely blocked KATP in diabetic but not in normal hearts, p < 0.05). A sarcolemmal KATP channel dysfunction might afford a primary approach to explain the absence of ischemic preconditioning protection against stunning in diabetic sheep.

Ischemic shortening of action potential duration as a result of KATP channel opening attenuates myocardial stunning by reducing calcium influx.

Action potential duration (APD) shortening due to opening of sarcolemmal ATP-dependent potassium (KATP) channels has been postulated to protect the myocardium against postischemic damage by reducing Ca2+ influx. This hypothesis was assessed, assuming that increased postischemic stunning due to KATP channel inhibition with glibenclamide could be reverted by the addition of the Ca2+ channel blocker diltiazem. Percent wall thickening fraction (%WTh, conscious sheep) and APD (open-chest sheep) were obtained from the following groups: control: 12 min ischemia by anterior descending coronary artery occlusion followed by 2 h reperfusion; glibenclamide: same as control, with glibenclamide (0.4 mg/kg) infused 30 min before ischemia; diltiazem: same as control, with diltiazem (100 microg/kg) administered prior to ischemia; glibenclamide+diltiazem: both drugs infused as in glibenclamide and diltiazem groups. APD was reduced in control ischemia. Conversely, KATP-channel blockade by glibenclamide lengthened APD and increased postischemic stunning (p < 0.01 vs. control); glibenclamide+diltiazem did not shorten APD but enhanced functional recovery (p < 0.01 vs. glibenclamide). Ca2+ channel blockade improvement of increased stunning provoked by KATP channel inhibition supports the hypothesis that APD shortening due to opening of KATP channels protects against postischemic stunning by limiting Ca2+ influx.

Ischemic preconditioning protection against stunning in conscious diabetic sheep: role of glucose, insulin, sarcolemmal and mitochondrial KATP channels.

INTRODUCTION: Sarcolemmal and mitochondrial ATP-sensitive potassium (KATP) channels have been postulated to participate in preconditioning protection against infarction and stunning. However, these structures appear to be altered in diabetes and thus, it would be possible that preconditioning does not develop in diabetic hearts. OBJECTIVE: The purpose of this study was to know whether early (EP) and late (LP) ischemic preconditioning against stunning develop in conscious diabetic (D) sheep and whether diabetes affects KATP channel function. METHODS: Male castrated sheep received alloxan monohydrate (1 g) and were ascribed to three experimental groups: control [DC, 12 min of ischemia (i) followed by 2 h of reperfusion (r)], early preconditioning (DEP, six 5 min i-5 min r periods were performed 45 min before the 12 min i) and late preconditioning (DLP, same as DEP except that the preconditioning stimulus was performed 24 h before the 12 min i). Regional mechanics during reperfusion was evaluated by wall thickening fraction (%WTH) and expressed as percentage of basal values (100%), and KATP channel behavior was indirectly assessed by monophasic action potential duration (MAPD) in relation to its sensitivity to glibenclamide blockade (0.1 and 0.4 mg/kg). The results were compared to those obtained in normal (N) sheep. The effects of sarcolemmal and mitochondrial KATP channel blockade on recovery from stunning were assessed by administration of glibenclamide (0.1 and 0.4 mg/kg) and 5-hydroxydecanoate (5-HD, 5 mg/kg i.v.) and/or diazoxide (10 microg/kg/min over 90 min). Whether acute hyperglycemia (H) in normal animals and insulin (I) treatment in diabetic sheep affected preconditioning protection and KATP channel behavior were also evaluated. RESULTS: Results expressed as mean % recovery of %WTH showed that preconditioning protected against stunning in normal sheep (NC=65+/-3.5, NLP=82+/-6**, NEP=76+/-4*, *P<0.05 and **P<0.01 against NC) while this did not occur in diabetic ones, where DLP (58+/-7.6) afforded a similar recovery to DC (54+/-5) and DEP worsened instead of improving mechanical function (37+/-9, P<0.01 against DC). Acute hyperglycemia did not affect preconditioning development (NEPH=72+/-3 and NLPH=80+/-4) and insulin treatment reverted the lack of early and late preconditioning protection in diabetic hearts (DEPI=72+/-4* and DLPI=76+/-3*, P<0.05 against DC). Sarcolemmal KATP channel behavior appeared altered in diabetic hearts as shown by MAPD in normal sheep (276+10 ms) compared to diabetic ones (365+9 ms, P<0.05) and by the sensitivity to glibenclamide [0.1 mg/kg completely blocked KATP channels in diabetic (P<0.05) but not in normal hearts]. Insulin also restored MAPD in diabetic heart. Mitochondrial KATP channels appeared not to account for the reported results in diabetes, since glibenclamide (%WTH=40+/-4, P<0.01 vs. NC), but not 5HD nor diazoxide affected myocardial functional recovery during reperfusion. CONCLUSIONS: Sarcolemmal KATP channel dysfunction due to the lack of insulin affords a primary approach to explain the absence of preconditioning protection against stunning in diabetic sheep hearts.

ATP-sensitive potassium channels do not have a main role in mediating late preconditioning protection against arrhythmias and stunning in conscious sheep.

OBJECTIVE: Although late preconditioning protects against stunning following several short periods of ischemia-reperfusion, it is not clear if it confers protection against stunning and malignant arrhythmias after a sustained reversible ischemia, and whether KATP channels are involved as triggers and/or end effectors of the protective mechanism. The purpose of this work was thus to test these issues in conscious sheep. METHODS: Five groups were considered: CONT (control): the animals were submitted to 12 min ischemia followed by 2 h reperfusion; SWOP (late preconditioning): on the first day, the animals were preconditioned with 6 periods of 5 min ischemia 5 min reperfusion and 24 h later they were submitted to 12 min ischemia followed by 2 h reperfusion; GLIB: same as CONT with the KATP channel inhibitor glibenclamide (0.4 mg/kg) infused 30 min prior to the 12 min ischemia; SWOPG2: same as SWOP with glibenclamide before the 12 min ischemia; SWOPG1: same as SWOP with glibenclamide prior to the preconditioning stimulus. RESULTS: Percent reperfusion recovery of wall thickening fraction (% WTh) showed late preconditioning protection against stunning throughout reperfusion (SWOP vs CONT, p < 0.01). Arrhythmia severity index (ASI) also demonstrated that late preconditioning protects against malignant arrhythmias at the onset of reperfusion (CONT: 4.87 +/- 1.62 vs SWOP: 1.39 +/- 0.93, p < 0.01). Glibenclamide was unable to prevent preconditioning, both against stunning and arrhythmia incidence, when administered either before the preconditioning stimulus (SWOPG1 vs CONT, p < 0.01) or before the sustained ischemia (SWOPG2 vs GLI, p < 0.01). CONCLUSIONS: Results indicate that late preconditioning protects against stunning and arrhythmias following a reversible, sustained ischemia in conscious sheep and that KATP channel participation is negligible as triggers and end effectors of both types of protection.

Atontamiento y preacondicionamiento isquémico en ovinos diabéticos conscientes. Rol de la hiperglucemia, hipoinsulinemia y de los canales de K+ dependientes de ATP / Stupefaction and ischemic preparation in conscious diabetic ovines. Role of hyperglycemia, hypoinsulinemia and of the K+ channels dependent of ATP

Introducción: los canales de potasio dependientes de ATP (KATP) del sercolema participan de la protección por preacondicionamiento contra el infarto y el atontamiento. Sin embargo, estas estructuras parecen estar alteradas en la diabetes y por lo tanto, es probable que el preacondicionamiento no se desarrolle en el miocardio diabético. La hiperglucemia y la hipoinsulinemia han demostrado afectar la función del canal KATP y en consecuencia podrían también jugar un rol en la respuesta del miocardio diabético a eventos de isquemia y reperfusión. Objetivo: la finalidad de este estudio fue saber si el preacondicionamiento isquémico temprano o primera ventana de protección (P) y el preacondicionamiento tardío o segunda ventana de protección (S) protegen contra el atontamiento en ovejas diabéticas (D) conscientes, determinar si la diabetes afecta la función de los canales de KATP y analizar cómo la hipoinsulinemia y/o la hiperglucemia afectan el desarrollo de preacondicionamiento. Métodos: ovinos machos castrados recibieron monohidrato de aloxán (1 gr) y posteriormente fueron asignados a tres grupos experimentales: a) control (C) [CD, 12 min de isquemia (i) y 2 hs de reperfusión (r)], b) preacondicionamiento temprano (PD, con seis episodios de 5 min i/5 min de r realizados 45 min antes de los 12 min de i) y c) preacondicionamiento tardío (SD, igual que PD excepto que el estímulo preacondicionante se realizó 24 hs antes de los 12 min de i). la mecánica regional durante la reperfusión fue evaluada mediante el cálculo de la fracción de espesamiento parietal (porcientoEP) que fue expresada en porcentaje respecto del valor basal considerado como cien por cien. Los resultados mecánicos se compararon con aquellos obtenidos en iguales protocolos experimentales en animales normales (N). El comportamiento de los canales KATP se determinó indirectamente midiendo la duración del potencial de acción monofásico (PAM) y la sensibilidad del mismo bloqueo con glibenclamida (G) 0,1 y 0,4 mg/kg enovejas normales y diabéticas a tórax abierto. La participación de los canales KATP sarcolemales en la recuperación del atontamiento también se evaluo en animales conscientes mediante la adminsitración de glibenclamida en iguales dosis a las utilizadas para el estudio de los PAM... (TRUNCADO)

Atontamiento y preacondicionamiento isquémico en ovinos diabéticos conscientes. Rol de la hiperglucemia, hipoinsulinemia y de los canales de K+ dependientes de ATP / Stupefaction and ischemic preparation in conscious diabetic ovines. Role of hyperglycemia, hypoinsulinemia and of the K+ channels dependent of ATP

Introducción: los canales de potasio dependientes de ATP (KATP) del sercolema participan de la protección por preacondicionamiento contra el infarto y el atontamiento. Sin embargo, estas estructuras parecen estar alteradas en la diabetes y por lo tanto, es probable que el preacondicionamiento no se desarrolle en el miocardio diabético. La hiperglucemia y la hipoinsulinemia han demostrado afectar la función del canal KATP y en consecuencia podrían también jugar un rol en la respuesta del miocardio diabético a eventos de isquemia y reperfusión. Objetivo: la finalidad de este estudio fue saber si el preacondicionamiento isquémico temprano o primera ventana de protección (P) y el preacondicionamiento tardío o segunda ventana de protección (S) protegen contra el atontamiento en ovejas diabéticas (D) conscientes, determinar si la diabetes afecta la función de los canales de KATP y analizar cómo la hipoinsulinemia y/o la hiperglucemia afectan el desarrollo de preacondicionamiento. Métodos: ovinos machos castrados recibieron monohidrato de aloxán (1 gr) y posteriormente fueron asignados a tres grupos experimentales: a) control (C) [CD, 12 min de isquemia (i) y 2 hs de reperfusión (r)], b) preacondicionamiento temprano (PD, con seis episodios de 5 min i/5 min de r realizados 45 min antes de los 12 min de i) y c) preacondicionamiento tardío (SD, igual que PD excepto que el estímulo preacondicionante se realizó 24 hs antes de los 12 min de i). la mecánica regional durante la reperfusión fue evaluada mediante el cálculo de la fracción de espesamiento parietal (porcientoEP) que fue expresada en porcentaje respecto del valor basal considerado como cien por cien. Los resultados mecánicos se compararon con aquellos obtenidos en iguales protocolos experimentales en animales normales (N). El comportamiento de los canales KATP se determinó indirectamente midiendo la duración del potencial de acción monofásico (PAM) y la sensibilidad del mismo bloqueo con glibenclamida (G) 0,1 y 0,4 mg/kg enovejas normales y diabéticas a tórax abierto. La participación de los canales KATP sarcolemales en la recuperación del atontamiento también se evaluo en animales conscientes mediante la adminsitración de glibenclamida en iguales dosis a las utilizadas para el estudio de los PAM... (TRUNCADO) (AU)

Estudio y caracterización de la aptitud agrícola de los suelos y calidad de las aguas en el Valle El Maitén-Chubut-Argentina

Presenta estudios físicos necesarios para el aprovechamiento ordenado con fines de irrigación contemplado en el desarrollo de zonas áridas-semiáridas de los suelos del Alto Río Chubut