Comparison of the protective effects of ischemic preconditioning and the Na+ /H+ exchanger blockade

The protective effects of ischemic preconditioning (IP) and Na+/H+ exchanger blockade (NHEb) by two blockers [ethylisopropylamiloride (EIPA) and HOE 642] were compared in the isovolumic perfused rat heart. The impairment in systolic and diastolic function detected in control ischemic hearts (C) exposed to 20 min of ischemia and 30 min of reperfusion was diminished in similar extent by IP and by NHEb with EIPA and HOE 642. At the end of the reperfusion period +dP/dtmax values were 57±9% in C hearts and 94±6%, 82±6% and 104±6% after IP and NHEb with EIPA and HOE 642, respectively. A depletion of ATP levels detected in C hearts after reperfusion (from 20.2±0.8 µmol/g dry weight before ischemia to 6.9±0.7 µmol/g dry weight) was partially prevented by both IP and NHEb with EIPA (9.2±0.7 µmol/g dry weight and 11.1±0.5 µmol/g dry weight, respectively). The ischemic contracture (IC), assessed by the left ventricular end diastolic pressure (LVEDP), observed in C hearts (35±4 mmHg) was not decreased by IP (40±4 mmHg) but it was prevented by NHEb (18±4 mmHg and 10±3 mmHg with EIPA and HOE 642, respectively). The ATP levels at the end of the ischemic period were similar in C and IP hearts (4.1±0.2 µmol/g dry wt vs. 3.3±0.4 µmol/g dry wt) but they were significantly higher after NHEb with HOE 642 (7.0±1.0 µmol/g dry wt). PKC inhibition by chelerythrine abolished the protection induced by IP after reperfusion although not the improvement induced by NHEb with EIPA.Facultad de Ciencias Exacta

Data supporting the cardiac mitochondria calcium handling in female normotensive and spontaneously hypertensive rats

In association with the published article "Mitochondrial calcium handling in normotensive and spontaneously hypertensive rats: correlation with systolic blood pressure levels", this data article contains information about calcium handling of cardiac mitochondria isolated from female of both rats strains (WKY and SHR). Dataset of mitochondrial permeability transition pore (mPTP) resistance to opening Ca2+-mediated, Ca2+ retention capacity (CRC), time constants and mitochondrial membrane potential (ΔΨm) are showed.Centro de Investigaciones Cardiovasculare

Dissociation between myocardial relaxation and diastolic stiffness in the stunned heart: its prevention by ischemic preconditioning

The effects of myocardial stunning and ischemic preconditioning on left-ventricular developed pressure and end-diastolic pressure (diastolic stiffness) as well as on coronary-perfusion pressure were examined in isolated isovolumic rabbit hearts. The isovolumic relaxation was evaluated, and the time constant of pressure decay during the isovolumic period was calculated. Our experimental protocol comprised: 1) myocardial stunning-global ischemia (15 min) followed by reperfusion (30 min); 2) myocardial stunning-global ischemia (20 min) followed by reperfusion (30 min); and 3) ischemic preconditioning — a single cycle of brief global ischemia and reperfusion (5 min each), before a second ischemic period, of 20-min duration. There was no effect upon systolic and diastolic parameters when 15 and 20 minutes of ischemia were evaluated. In both stunned groups the left ventricular developed pressure first recovered to near control values, but then stabilized at only 60% of the control values. Whereas the isovolumic relaxation time constant was increased after 5 min of reperfusion, and return to control values at late reperfusion, the end diastolic pressure remained elevated during the entire period. Values of dP/dV calculated at common pressure levels, were used as a second index of diastolic stiffness. They were increased after stunning, as also was the coronary perfusion pressure. When the heart was preconditioned with a single episode of ischemia, the systolic and diastolic alterations were completely abolished. We thus concluded that diastolic abnormalities incurred by myocardial stunning consist in both an increase in diastolic stiffness and an early impairment of isovolumic relaxation. The increase in stiffness cannot result from incomplete relaxation since these two parameters become temporally dissociated during the reperfusion period.Centro de Investigaciones Cardiovasculare

NHE-1 and NHE-6 Activities : Ischemic and Reperfusion Injury

The study published in this issue of Circulation Research showing that a null mutation of NHE-1 improves the tolerance of the heart to ischemia and reperfusion (I/R) is an important contribution for the following reasons: (1) In the animals with null mutation, contracture during the ischemic period was less and ATP levels were preserved compared with wild-type animals. This observation, on the one hand, provides evidence that protection by downregulation of NHE-1 during the ischemic period itself is indeed possible and, on the other hand, it argues against the suggestion that the exchanger is inactive during this same period. (2) In contrast with chronic blockade of the NHE-1 by pharmacological interventions, the long-term absence of the exchanger does not elicit major compensatory changes that, in turn, might negate the cardioprotective effect of blocking its activity for a relative short term. This point is related to a recent publication showing that long-term treatment with the NHE-1 blocker cariporide is followed by an upregulation of the functional units of the exchanger in a similar way to the well-known tolerance phenomenon following β-adrenergic receptor blockade. The absence of such upregulation negates possible hypersensitivity to ischemia upon withdrawal of the medication. The risk is evident in hearts with upregulation of NHE-1, which gain Na+i more rapidly during ischemia, and show impaired recovery after reperfusion. (3) No additional protection was obtained by adding the NHE-1 blocker eniporide to the NHE-1 null mice, suggesting that there is not another NHE isoform that can be blocked with this compound to add additional protection; the findings additionally hint that the attenuation of the injury obtained by the absence of the sarcolemmal NHE-1 is maximal and, therefore, no further beneficial effect will be detected by blocking the mitochondrial NHE (MNHE).Facultad de Ciencias MédicasCentro de Investigaciones Cardiovasculare

Comparison of the protective effects of ischemic preconditioning and the Na+ /H+ exchanger blockade

The protective effects of ischemic preconditioning (IP) and Na+/H+ exchanger blockade (NHEb) by two blockers [ethylisopropylamiloride (EIPA) and HOE 642] were compared in the isovolumic perfused rat heart. The impairment in systolic and diastolic function detected in control ischemic hearts (C) exposed to 20 min of ischemia and 30 min of reperfusion was diminished in similar extent by IP and by NHEb with EIPA and HOE 642. At the end of the reperfusion period +dP/dtmax values were 57±9% in C hearts and 94±6%, 82±6% and 104±6% after IP and NHEb with EIPA and HOE 642, respectively. A depletion of ATP levels detected in C hearts after reperfusion (from 20.2±0.8 µmol/g dry weight before ischemia to 6.9±0.7 µmol/g dry weight) was partially prevented by both IP and NHEb with EIPA (9.2±0.7 µmol/g dry weight and 11.1±0.5 µmol/g dry weight, respectively). The ischemic contracture (IC), assessed by the left ventricular end diastolic pressure (LVEDP), observed in C hearts (35±4 mmHg) was not decreased by IP (40±4 mmHg) but it was prevented by NHEb (18±4 mmHg and 10±3 mmHg with EIPA and HOE 642, respectively). The ATP levels at the end of the ischemic period were similar in C and IP hearts (4.1±0.2 µmol/g dry wt vs. 3.3±0.4 µmol/g dry wt) but they were significantly higher after NHEb with HOE 642 (7.0±1.0 µmol/g dry wt). PKC inhibition by chelerythrine abolished the protection induced by IP after reperfusion although not the improvement induced by NHEb with EIPA.Facultad de Ciencias Exacta

Papel de la glucógeno sintetasa cinasa 3β (GSK-3β) en el pre y postacondicionamiento isquémicos en ratas hipertensas espontánea

Estudios recientes en animales normotensos muestran que la enzima glucógeno sintetasa cinasa 3β (GSK-3β) es una de las potenciales cinasas que pueden regular la formación y/o apertura del poro de transición mitocondrial (PTM). La GSK-3β es constitutivamente activa y es inactivada por fosforilación en Ser 9. En estas condiciones es capaz de interactuar con los principales componentes del PTM e impedir su apertura

Effects of ischemic postconditioning on isolated hearts of males and females

Nuestro objetivo fue determinar los efectos del posacondicionamiento isquémico (PCI) sobre las alteraciones miocárdicas producidas por la isquemia- reperfusión en ratas Wistar macho (M) y hembra (H). Los corazones aislados y perfundidos por el sistema de Langendorff, fueron asignados a los grupos: 1) Control no isquémico (C): perfusión durante 90 minutos (min); 2) Control isquémico (CI): 30 min de isquemia global (IG) y 60 min de reperfusión (R); 3) PCI: 3 ciclos de 30 segundos (s) de IG y 30 s de R se aplicaron al inicio de R. Se midió el tamaño del infarto (TI). La función sistólica se evaluó a través de la presión desarrollada del ventrículo izquierdo (PDVI) y la velocidad máxima de ascenso de la presión (+dP/dtmáx); la diastólica a través de la velocidad máxima de descenso de la presión (−dP/dtmáx), el tiempo hasta la mitad de la relajación (t50), la constante de tiempo de relajación (τ) y la presión diastólica final del ventrículo izquierdo (PDFVI). En CI el TI fue mayor en M que en H (40 ± 2% vs. 29 ± 4%, p<0,05). Los valores de PDVI y +dP/dtmáx fueron 19 ± 4% y 23 ± 5% en M y de 55 ± 3% y 59 ± 7% en H (p<0,05). La –dP/dtmáx fue 21 ± 4% para M y 54 ± 7% para H (p<0,05) y la PDFVI fue 50 ± 4 mmHg para M y 26 ± 8 mmHg para H (p<0,05). El t50 no mostró cambios: aumentó a los 5 y 10 min de R y se normalizó al final de R sólo en M. El PCI disminuyó el TI en M y H (16 ± 1% y 15 ± 1%, p<0,05), pero aumentó la recuperación posisquémica de la función miocárdica solo en M. Estos resultados muestran que: 1) el TI fue menor y la recuperación contráctil posisquémica fue mayor en H que en M; 2) el PCI disminuyó el TI en M y H, pero mejoró la respuesta contráctil posisquémica sólo en M. Estos datos sugieren que el PCI es una herramienta cardioprotectora más efectiva en M que en H.Our objective was to determine the effects of ischemic postconditioning (IPC) on myocardial alterations caused by ischemia-reperfusion in male (M) and female (F) young adult (4-5 months old) Wistar rats. After a 20-min stabilization period, isolated hearts perfused by the Langendorff system were assigned to the following experimental groups: 1) Non-ischemic control (NIC): perfusion for 90 min; 2) Ischemic control (IC): 30-min global ischemia (GI) and 60-min reperfusion (R); 3) IPC: 3 cycles of 30 sec of GI and 30 sec of R at the beginning of R. Infarction size (IS) was determined by TTC staining technique. Systolic function was assessed by the developed pressure of left ventricle (LVDP) and the maximum rate of rise of left ventricular pressure (+dP/dtmax). Diastolic function was measured using the maximum rate of decrease of left ventricular pressure (–dP/dtmax), half-relaxation time (t50), time constant of relaxation (τ) and left ventricular end diastolic pressure (LVEDP) as an index of diastolic stiffness. In the IC group the IS was significantly higher in M than F (40 ± 2% vs. 29 ± 4%, respectively; p&lt;0.05). At the end of R, LVDP and +dP/dtmax were higher in F compared to M. The values were 19 ± 4% and 23 ± 5% for M and 55 ± 3% and 59 ± 7% for F (p&lt;0.05). Similarly the –dP/dtmax was higher in F than M (54 ± 7% and 21 ± 4%, respectively; p&lt;0.05). LVEDP was 50 ± 4 mmHg for M and 26 ± 8 mmHg for F (p&lt;0.05). t50 did not change in M and F, increased at 5 and 10 min of R and normalized at the end of R only in M. IPC significantly decreased IS in hearts from both sexes (16 ± 1% and 15 ± 1% for M and F, respectively) but increased the post-ischemic recovery of systolic and diastolic myocardial function only in M. These results show that in Wistar rats young adults: 1) IS and post-ischemic myocardial function was significantly higher in M than F; 2) IPC decreased IS in hearts from both sexes; 3) IPC improved post-ischemic recovery of myocardial function in M but did not modify it in F. These data suggest that IPC is a more effective cardioprotective tool in M than in F.Centro de Investigaciones Cardiovasculare

Respuesta al calcio de mitocondrias de ratas normotensas e hipertensas espontáneas: relación con la presión arterial

Trabajos previos muestran que en animales hipertensos la homeostasis de Ca2+ está alterada, pero los mecanismos involucrados no están totalmente dilucidados. El objetivo fue evaluar la respuesta al Ca2+ de mitocondrias aisladas de ratas normotensas Wistar Kyoto (WKY) e hipertensas espontáneas (SHR) y establecer una posible relación con la presión arterial sistólica (PAS). Medimos la capacidad de retención de Ca2+ (CRC) por el método de Calcium green 5N, analizando el número de pulsos de Ca2+ (NP), el tiempo total (Tt, seg) y el tiempo de cada pulso (Tp, seg), necesarios para abrir el poro de permeabilidad transitoria de la mitocondria (PPTM).Facultad de Ciencias Médica

Respuesta al calcio de mitocondrias de ratas normotensas e hipertensas espontáneas: relación con la presión arterial

Trabajos previos muestran que en animales hipertensos la homeostasis de Ca2+ está alterada, pero los mecanismos involucrados no están totalmente dilucidados. El objetivo fue evaluar la respuesta al Ca2+ de mitocondrias aisladas de ratas normotensas Wistar Kyoto (WKY) e hipertensas espontáneas (SHR) y establecer una posible relación con la presión arterial sistólica (PAS). Medimos la capacidad de retención de Ca2+ (CRC) por el método de Calcium green 5N, analizando el número de pulsos de Ca2+ (NP), el tiempo total (Tt, seg) y el tiempo de cada pulso (Tp, seg), necesarios para abrir el poro de permeabilidad transitoria de la mitocondria (PPTM).Facultad de Ciencias Médica

Data supporting the cardiac mitochondria calcium handling in female normotensive and spontaneously hypertensive rats

In association with the published article "Mitochondrial calcium handling in normotensive and spontaneously hypertensive rats: correlation with systolic blood pressure levels", this data article contains information about calcium handling of cardiac mitochondria isolated from female of both rats strains (WKY and SHR). Dataset of mitochondrial permeability transition pore (mPTP) resistance to opening Ca2+-mediated, Ca2+ retention capacity (CRC), time constants and mitochondrial membrane potential (ΔΨm) are showed.Centro de Investigaciones Cardiovasculare