| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Laboratorio de Cardiología Experimental, Servicio de Cardiología, Hospital Vall d'Hebron, 08035 Barcelona, Spain
Submitted 12 May 2003 ; accepted in final form 9 July 2003
 |
ABSTRACT |
|---|
 TOP ABSTRACT MATERIALS AND METHODSRESULTSDISCUSSIONDISCLOSURESREFERENCES |
|---|
myocardial ischemia; gap junctions
and MAPKs seem to play a critical role (21, 22). However, very little is known on the end-effector mechanisms by which preconditioning prevents cell death.
It has been hypothesized that one of these end-effector mechanisms could involve gap junctions. This hypothesis is based in two lines of evidence. First, gap junctions have been shown to allow spreading of different types of cell death in different tissues under different conditions (8, 13, 24, 26, 32). In cardiomyocytes, gap junction-mediated communication allows cell-to-cell propagation of hypercontracture (36), and this phenomenon seems to significantly contribute to the final extent and geometry of cell death in reperfused infarcts (13). Gap junctions play a critical role in the propagation of electrical impulse in the heart, and its conductivity has been shown to be reduced and eventually abolished during ischemia (4, 11) and rapidly restored during reperfusion (33). Second, gap junction-mediated communication between cardiomyocytes is tightly regulated by changes in the phosphorylation state of connexin43 (Cx43), the protein of which gap junction channels connecting ventricular myocytes are made (42). Depending on the site, phosphorylation of Cx43 may increase or reduce gap junction conductance. In particular, PKC- and MAPKs, the most prominent kinases involved in the preconditioning cascade, are known to regulate Cx43 phosphorylation and function. The marked effects of IPC on Cx43 phosphorylation has been very recently demonstrated in two separate studies (19, 39). It appears thus plausible that IPC could exert its protective effect through a reduction in gap junction-mediated spreading of necrosis at the time of reperfusion.
In a recent study, Schwanke et al. (40) provided strong evidence for the involvement of Cx43 in the protective effect of preconditioning and suggested a role of this protein in cell volume regulation. This study convincingly shows that underexpression of Cx43 in a transgenic model does not modify the extent of necrosis induced by ischemia-reperfusion but completely abolishes preconditioning protection.
Other studies have suggested an involvement of gap junctions or Cx43 in ischemic preconditioning. Daleau et al. (9) described increased Cx43 levels in ischemic rabbit hearts compared with nonpreconditioned hearts. Li et al. (23) found that in isolated mice hearts, the administration of the gap junction blocker heptanol before preconditioning ischemia abolished its protective effect. However, it is also possible that the role of Cx43 in preconditioning is independent from gap junction-mediated communication. Recent proteomic studies have disclosed that Cx43 participates in the formation of signaling complexes that may play a critical role in the cellular response to PKC- activation (31). On the other hand, a very recent study by Lin et al. (25) clearly demonstrated that the forced expression of Cx43 has a protective effect against cell death secondary to different types of cell injury in astrocytes. This effect is independent of any effect of Cx43 overexpression on gap junction function (25).
The present study investigates whether the role of Cx43 in the protective effect of IPC is mediated by a reduction of gap junction permeability and a limited gap junction-mediated spreading of cell death during ischemia-reperfusion. To this purpose, myocardial electrical impedance and velocity of propagation of the transmembrane action potential (TAP) were analyzed in isolated rat hearts submitted to ischemia, and the observations on electrical impedance under in vivo conditions were validated in pigs submitted to transient coronary occlusion.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONDISCLOSURESREFERENCES |
|---|
TAP recordings. TAPs were recorded from the apical region of the heart with conventional glass microelectrodes filled with 3 M KCl, with a tip resitance of 30–40 M
. The microelectrodes were connected via Ag-AgCl interfaces to high-input impedance amplifiers (VF-102 and IS-100, Biologic; Claix, France), and the signal was displayed on a digital storage oscilloscope (CS-8010, Kenwood), digitized at 10 kHz, and stored for further analysis as previously described (33, 34). Conduction time was measured as the time between the stimulus and the onset of rapid depolarization of the action potential. The distance between the stimulating electrode and the recording microelectrode was 5–7 mm. Conduction block was defined as complete loss of excitability.
Myocardial electrical impedance. Tissue electrical impedance is better characterized by measuring its two components: the in-phase component of voltage (V) with respect to current intensity (I) (i.e., the tissue resistance, R) and the phase angle (
) (3). represents the time delay between the voltage and intensity waves because biological tissues are not purely resistive and the capacitance of cell membranes must be taken into account (Fig. 1). Myocardial impedance was measured by using a four-electrode probe (6) that was inserted in the septum. The probe had four platinum electrodes (length 5 mm, diameter 0.4 mm) that were separated 2.5 mm, one from each other. An alternating current (10 µA, 7 kHz) was applied through the outer pair of electrodes, and the inner pair of electrodes continuously recorded the components of voltage (model 5110; high-input impedance lock-in amplifier, Princeton Applied Research). The frequency of the applied current was 7 kHz because this frequency maximizes differences in between the normal and ischemic myocardium without impairing the discriminating value of resistance measurements (3). TAP recordings and analysis of electrical impedance were always performed far way from the incision made to expose the endocardial surface of the LV, and their normality and stability during the equilibration period were always checked before the experiment was started.
|
Analysis of rigor contracture and electrical uncoupling during ischemia. Rigor contracture was detected as an increase in resting tension during ischemia, and its onset was defined when its value reached an increase of 10% over its value at 10 min of ischemia (33). The effects of ischemia on myocardial tissue impedance had previously been characterized by the analysis of changes in measurements of R and (3, 6, 33). Ischemia induces a initial slight increase in R and corresponding decrease in , which is followed by a second phase of a sharp increase in R and decrease in (6). This second phase is related to cell-to-cell electrical uncoupling (20, 29). The time of onset of these abrupt changes was determined as the time of intersection of the two tangent lines superimposed on the original trace recording as previously described (33).
Experimental protocol. After 40 min of equilibration, 17 hearts were submitted to 1 h of no-flow ischemia, and the preparation was superfused with hypoxic Krebs solution (bubbled with 95% N2-5% CO2, pH 7.4) to maintain the temperature between 35.5 and 36°C. Eight hearts were submitted to two cycles of 5 min of ischemia followed by 5 min of reperfusion before the 1-h period of ischemia (IPC group). After the 60-min period of ischemia, all hearts were reperfused for 1 h, and lactate dehydrogenase release was determined in the effluent.
Studies in the in situ pig heart. Twenty-nine large white pigs (weight 40.1 ± 1.3 kg) were premedicated with 10 mg/kg im azaperone 30 min before being anesthetized with 30 mg/kg iv thiopental. Subsequently, they were intubated and mechanically ventilated with room air. One femoral artery and two femoral veins were catheterized with 5-Fr sheaths by the Seldinger method. Anesthesia was maintained with a continuous infusion of thiopental. A midline sternotomy was performed, and the left anterior descending coronary artery (LAD) was dissected free at its midpoint and surrounded by an elastic snare. To monitor regional myocardium contractility, two pairs of ultrasonic crystals were inserted into the inner third of the LV free wall: one pair in the territory depending of the LAD (area at risk) and the other one in the circumflex territory (control area) (15). End-diastolic segment length (EDSL) and end-systolic segment length (ESSL) were defined as the distance between crystals at end diastole and end systole, respectively. Systolic shortening (SS) was calculated as the difference between EDSL and ESSL divided by EDSL. A pressure transducer catheter (Mikro-tip, Millar Instruments) was advanced into the LV, and a transit time flow probe (T-106, Transonic Systems) was placed around the LAD in the point where it was dissected to monitor coronary blood flow. Myocardial electrical impedance was measured using the same four-electrode probe than in the isolated rat hearts. The probe was inserted in the area at risk, perpendicular to the LAD. The tips of the electrodes, with a length of 5 mm, allowed analysis of changes in the electrical impedance in the midmyocardial layer of the LV wall, a zone where the effects of IPC on myocardial salvage were most evident.
Arterial pH, PO2, and PCO2 were monitored, and ventilatory parameters were adjusted to keep them between normal limits. Body core temperature was measured using a thermometer placed in the eosophagus, and body temperature was maintained between 36.5°C and 37.5°C with the aid of an thermal blanket. Hematological and biochemical determinations were performed before sternotomy and at the end of the experiment. Lead II of the ECG, aortic pressure, left ventricular pressure, coronary blood flow, and ultrasonic crystals signals were amplified and digitized at a sampling rate of 100 Hz/channel (Power Lab/SP16 Hardward, ADInstruments; Castle Hill, Australia). The signals were continuously registered with the commercially available software Chart for Windows v3.4.6 (ADInstruments).
Study protocol. The animals were submitted to a 48-min coronary occlusion (CO) of the LAD followed by 2 h of reperfusion. Previously, the animals had been allocated to one of two groups of treatment: 1) control (n = 17); and 2) IPC (n = 12), in which the 48-min CO was immediately preceded by two periods of CO of 5 min, each of them followed by 5 min of reperfusion.
Ischemic rigor contracture and tissue impedance in vivo. The development of rigor contracture was studied by analyzing changes in the maximal amplitude of passive cyclic segment length changes in the ischemic myocardium, as previously described (12). Rigor onset was defined as the time at which this amplitude started to diminished and was less than the value measured 5 min after CO. R and measurements were performed every 10 s, and their values were recorded for later off-line analysis.
Area at risk and infarct size. After 2 h of reperfusion, the LAD was reoccluded, and 5 ml of 10% fluorescein were injected into the left atrium. The heart was excised, cooled at 4°C, and cut into 5- to 7-mm slices perpendicular to its long axis. The slices were weighted in a precision balance (Precisa 180 A; Zurich, Switzerland), and their basal face was illuminated under ultraviolet light to outline the area at risk. Digital photographs of the slices were obtained (Olympus Digital Camera C-1400L, Olympus Optical; Tokyo, Japan). The slices were immersed during 10 min in a 1% triphenyltetrazolium chloride (TTC) solution, buffered at pH 7.4, and they were imaged again under white light. The negative reaction to the TTC was identified as necrotic tissue. An investigator blinded to the procedure measured the area at risk and the necrotic myocardium by using the commercially available software MicroImage (Olympus Optical; Hamburg, Germany). The masses of the area at risk and necrotic myocardium were calculated from these measurements and from the weight of the slices.
Statistical analysis. Statistical analysis was performed using commercially available software (SPSS for Windows 8.0). The homogeneity between groups was tested by t-test for independent samples. Changes in segment length and physiological parameters were studied by means of the mean ANOVA test. Differences in qualitative variables were assessed by the 
2-test. A P value of 0.05 was used for all tests. Values are expressed as means ± SE.
|
RESULTS |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONDISCLOSURESREFERENCES |
|---|
Ischemia induced a progressive reduction in resting membrane potential, a decrease in the amplitude of the action potential, and a progressive decrease in conduction velocity, without differences between groups (Fig. 2). Conduction block occurred at 13.8 ± 1.0 min of ischemia in the control group and at 13.4 ± 0.7 min of ischemia in the preconditioned hearts (P = not significant, Fig. 3).
|
|
Myocardial impedance was markedly altered by ischemia. A significant increase in R was observed in the control and preconditioned hearts (from 93.6 ± 6.3 to 182.3 ± 11.2 · cm and from 94.4 ± 9.8 to 162.9 ± 20.6 · cm at 45 min of ischemia, respectively, P = not significant). experienced a significant reduction during ischemia (from –0.44 ± 0.3° to –4.59 ± 0.3° and from –0.85 ± 0.6° to –3.98 ± 0.7° in the control and IPC groups, respectively, P = not significant). Reperfusion was associated with a rapid return of R and to values close to those measured before ischemia, without between-groups differences.
Reperfusion-induced lactate dehydrogenase release was significantly reduced in the group with IPC (58.0 ± 13.6 vs. 169.7 ± 50.38 U · g dry tissue–1 · 30 min–1, P < 0.05).
Studies in the in situ pig heart. Two animals from the control group died due to intractable ventricular fibrillation (VF), one during ischemia and the other during reperfusion. Three animals from the IPC group developed reocclusion of the LAD during reperfusion and were excluded from final analysis.
There were no differences in body core temperature between control and preconditioned animals either at the onset of sustained CO (37.2 ± 0.2 vs. 37.1 ± 0.2°C), at the end of CO (37.1 ± 0.3 vs. 36.8 ± 0.3°C), or at the end of reperfusion (36.6 ± 0.1 vs. 36.8 ± 0.2°C). There were no significant between-group differences in heart rate, mean aortic pressure, or coronary blood flow, whereas LV diastolic pressure after 15 min of reperfusion was significantly lower in the IPC group with respect to the placebo (Table 1). EDSL in the area at risk showed a marked increase during ischemia and a rapid reduction on reperfusion, reflecting hypercontracture (1), without between-groups differences. Systolic shortening was abolished during ischemia and showed minimal or no recovery during reperfusion, independently of treatment.
|
The onset of ischemic rigor contracture occurred at 14.4 ± 1.5 and at 13.2 ± 2.7 min in control and preconditioned hearts, respectively (P = not signficant) (Fig. 4). At the end of CO, the amplitude of segment length was significantly reduced in both control and IPC groups (53.1 ± 6.1% and 60.6 ± 8.5% of its value at 5 min of CO) without differences between groups (Fig. 4). The preconditioning episodes had a slight effect on myocardial tissue impedance. During subsequent index ischemia, there was an increase in R and a decrease in (increase in time delay between V and current waves). The rate of these changes showed a marked acceleration at 15–25 min of CO (Fig. 5). The steep change in R started at 22.9 ± 1.0 min in controls and at 23.0 ± 0.8 min in preconditioned hearts (P = not signifcant, Fig. 5). The rapid fall in occurred at 23.5 ± 1.0 min in control animals and at 23.8 ± 1.0 min in the IPC group animals. There was a very close correlation between the occurrence of R and rapid changes (r = 0.996, P < 0.001). During early reperfusion, R and values rapidly recovered in both groups achieving values nearly identical to preischemic ones without differences between groups (Fig. 5).
|
|
Phase 1b ectopic ventricular beats (EVB) presented its maximal incidence around 25 min of occlusion in both groups. The total ischemic EVB were 24.8 ± 9.0 and 57.8 ± 18.7 for control and IPC groups, respectively (P = not significant). Four animals in the control group and four animals in the IPC group developed ventricular fibrillation (VF) during ischemia without significant differences between groups. During the first minutes of reperfusion 26.6% of control animals and 33.3% of preconditioned animals presented VF (P = not significant).
The area of myocardium at risk was nearly identical in both groups (12.5 ± 0.8 and 11.6 ± 0.8% of ventricular mass, for control and IPC groups, respectively, P = not significant), but infarct size was significantly reduced in the IPC group (16.1 ± 4.8% of the area at risk compared with 45.9 ± 9.1% in controls, P = 0.01).
|
DISCUSSION |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONDISCLOSURESREFERENCES |
|---|
It has been shown that the abrupt increase in tissue resistivity and phase angle shift observed in ischemic myocardium reflects the onset of cell-to-cell electrical uncoupling (20). This onset shows a close temporal correlation with the development of ischemic rigor contracture (4) and the initiation of the rise in cytosolic Ca2+ concentration in cardiomyocytes (11). The reduction in gap junction conductivity within a single cell appears to be progressive and has no significant effect on impulse propagation until it is severe (safety factor). Previous studies suggest that a certain gap junction permeability may persist far beyond the onset of rigor contracture and electrical uncoupling (37).
Previous studies. Other authors have analyzed the effect of IPC on the changes in myocardial electrical impedance induced by ischemia. Dekker et al. (11), by using the rabbit papillary muscle model, observed a slight delay in the onset of ischemic rigor contracture and electrical uncoupling in the preconditioned myocardium, an effect that was later attributed to Ca2+-dependent PKC activation (10). Another study by Tano et al. (41) in the rabbit papillary muscle found that preconditioning delayed the sharp increase in intracellular and total resistance during sustained ischemia without affecting conduction velocity. The reasons of the discrepancy between these studies and the present one are not clear. A potential explanation is the different animals (rabbit vs. rat) and models (papillary muscle vs. heart). Indeed, the delay in electrical uncoupling observed in the studies in the rabbit papillary muscle is consistent with the delay in the onset of rigor contracture observed in these studies, whereas the lack of delay observed in the present work is consistent with the observed lack of delay in the onset of rigor. This lack of protection of IPC against rigor contracture is consistent with previous studies in our laboratory in intact perfused rat hearts in which LV diastolic pressure was monitored with a LV balloon (18) and with many other studies in rat hearts (5, 16, 27). A very recent study (19) failed to detect a significant delay in the onset of uncoupling in preconditioned isolated rat hearts, although it described a slightly slower increase of electrical resistivity in preconditioned hearts with respect to controls, with a maximum nonsignificant difference of <5 min between the curves of resistance obtained in both groups.
A slight but statistically significant delay in the onset of uncoupling has been reported in an in situ pig heart model (6). In that study, 
-chloralose was used for anesthesia in contrast to our study in which deep thiopental anesthesia was used. Anesthesia with -chloralose increases the incidence of ventricular arrhythmias. More importantly, no control of body temperature was described. In the absence of such a control, the open-chest model induces a variable degree of hypothermia, which could explain the large interanimal variability in the onset of uncoupling observed in that study. In fact, the onset of uncoupling in the control group occurred 10 min later than in our study, in which temperature was strictly controlled and kept within narrow limits. The absence of significant effects of IPC on the time course of ischemic electrical uncoupling is in accordance with its small and variable effect (delay or acceleration) on rigor contracture (38), and it is in contrast with the marked delay in the onset of both changes induced by other protective interventions as hypothermia or Na+/H+ exchange inhibition (33).
In contrast to the effects of IPC on the time course of electrical uncoupling during ischemia, its effects on the recovery of electrical coupling during subsequent reperfusion have not been previously investigated. This information was very much needed because other studies have shown gap junction-mediated spreading of reperfusion-induced hypercontracture and a beneficial effect of pharmacological gap junction inhibition during early reperfusion on the final extent of myocardial necrosis (13). An effect of IPC on gap junction permeability was plausible because IPC induces changes in the phosphorylation status of many proteins (14), and the permeability of Cx43 gap junction channels is tightly regulated by phosphorylation at different sites (2, 21, 22). In fact, two very recent studies have clearly demonstrated that IPC attenuates the increase in nonphosphorylated Cx43 occurring during sustained ischemia in the pig (39) and the rat (19) myocardium. However, the present results clearly demonstrate the absence of any effect of IPC on myocardial electrical impedance during reperfusion and dissociate its protective effect against cell death from any effect on cell-to-cell spread of necrosis during this period.
Although the present study fails to detect any effect of IPC on cell-to-cell electrical coupling during sustained ischemia and subsequent reperfusion, it does not rule out the possibility that gap junction-mediated intercellular communication plays a role in the triggering of preconditioning during brief ischemic episodes. This possibility was recently suggested by Li et al. (23) by showing that administration of the gap junction uncoupler heptanol before a single episode of preconditioning ischemia abolishes protection in the mouse heart, whereas pretreatment with heptanol had no effect on infarct size in the absence of preconditioning ischemia (17).
Potential effects of Cx43 independent from gap junction-mediated communication. It has been suggested that the effect of IPC on Cx43 phosphorylation could contribute to protect myocytes during ischemia by preventing the opening of hemichannels that would allow water and Ca2+ influx (39, 40). Contreras et al. (7) described that metabolic inhibition resulted in opening of hemichannels in rat astrocytes, and they proposed that this could be an important mechanism of cell death under energy deprivation (7). The role of connexin hemichannels in the genesis of ischemic injury and the effect of IPC in this role remain to be elucidated.
According to the present results, the recently observed lack of inducibility of IPC protection in transgenic mice underexpressing Cx43 could be explained by other roles of Cx43 independent from cell-to-cell communication. Very recent observations in two separate lines of research support this hypothesis. Proteomic analysis has shown that Cx43 indeed participates in the formation of signaling complexes that may play a critical role in the cellular response to PKC- activation (31). On the other hand, Lin et al. (25) have shown that the forced expression of Cx43 has a protective effect against cell death secondary to different types of cell injury in astrocytes, including energy depletion (metabolic inhibition) and oxidative stress. This effect was preserved when cell-to-cell communication was prevented by the physical separation of cells, pharmacological inhibition of gap junction-mediated communication, or even when cells expressed mutant, nonfunctional Cx43. This observation supports the hypothesis that the protective effect of Cx43 overexpression is independent on any effect on gap-junction communication.
It has long been accepted that connexin synthesis, their intercellular traffic, and their function and degradation are intimately related to cell division, differentiation, and death (30, 35). Their role in cell survival during ischemia-reperfusion, and in particular, in the mechanism of the protection afforded by IPC needs to be investigated in depth.
|
DISCLOSURES |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONDISCLOSURESREFERENCES |
|---|
a SAF2002-00759 and Fondo de Investigación Sanitaria 01/3135. A. Rodriguez-Sinovas has a grant from the Ministerio de Sanidad y Consumo (99/3142). |
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
|
REFERENCES |
|---|
|
TOPABSTRACTMATERIALS AND METHODSRESULTSDISCUSSIONDISCLOSURESREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  M. Ruiz-Meana, A. Rodriguez-Sinovas, A. Cabestrero, K. Boengler, G. Heusch, and D. Garcia-Dorado Mitochondrial connexin43 as a new player in the pathophysiology of myocardial ischaemia-reperfusion injury Cardiovasc Res, January 15, 2008; 77(2): 325 - 333. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Miura, T. Yano, K. Naitoh, M. Nishihara, T. Miki, M. Tanno, and K. Shimamoto {delta}-Opioid receptor activation before ischemia reduces gap junction permeability in ischemic myocardium by PKC-{varepsilon}-mediated phosphorylation of connexin 43 Am J Physiol Heart Circ Physiol, September 1, 2007; 293(3): H1425 - H1431. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. C. Lascano and J. A. Negroni Gap junctions in preconditioning against arrhythmias Cardiovasc Res, June 1, 2007; 74(3): 341 - 342. [Full Text] [PDF]
|
|
|
|
|
|
K. Boengler, I. Konietzka, A. Buechert, Y. Heinen, D. Garcia-Dorado, G. Heusch, and R. Schulz Loss of ischemic preconditioning's cardioprotection in aged mouse hearts is associated with reduced gap junctional and mitochondrial levels of connexin 43 Am J Physiol Heart Circ Physiol, April 1, 2007; 292(4): H1764 - H1769. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Eckle, A. Grenz, D. Kohler, A. Redel, M. Falk, B. Rolauffs, H. Osswald, F. Kehl, and H. K. Eltzschig Systematic evaluation of a novel model for cardiac ischemic preconditioning in mice Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2533 - H2540. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Vetterlein, C. Muhlfeld, C. Cetegen, R. Volkmann, C. Schrader, and G. Hellige Redistribution of connexin43 in regional acute ischemic myocardium: influence of ischemic preconditioning Am J Physiol Heart Circ Physiol, August 1, 2006; 291(2): H813 - H819. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Rodriguez-Sinovas, K. Boengler, A. Cabestrero, P. Gres, M. Morente, M. Ruiz-Meana, I. Konietzka, E. Miro, A. Totzeck, G. Heusch, et al. Translocation of Connexin 43 to the Inner Mitochondrial Membrane of Cardiomyocytes Through the Heat Shock Protein 90-Dependent TOM Pathway and Its Importance for Cardioprotection Circ. Res., July 7, 2006; 99(1): 93 - 101. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Rodriguez-Sinovas, D. Garcia-Dorado, M. Ruiz-Meana, and J. Soler-Soler Protective effect of gap junction uncouplers given during hypoxia against reoxygenation injury in isolated rat hearts Am J Physiol Heart Circ Physiol, February 1, 2006; 290(2): H648 - H656. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Boengler, G. Dodoni, A. Rodriguez-Sinovas, A. Cabestrero, M. Ruiz-Meana, P. Gres, I. Konietzka, C. Lopez-Iglesias, D. Garcia-Dorado, F. Di Lisa, et al. Connexin 43 in cardiomyocyte mitochondria and its increase by ischemic preconditioning Cardiovasc Res, August 1, 2005; 67(2): 234 - 244. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Rodriguez-Sinovas, D. Garcia-Dorado, P. Pina, M. Ruiz-Meana, and J. Soler-Soler Effect of sarcolemmal rupture on myocardial electrical impedance during oxygen deprivation Am J Physiol Heart Circ Physiol, March 1, 2005; 288(3): H1396 - H1403. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. Turner, G. A. Haywood, P. Andreka, L. You, P. E. Martin, W. H. Evans, K. A. Webster, and N. H. Bishopric Reversible Connexin 43 Dephosphorylation During Hypoxia and Reoxygenation Is Linked to Cellular ATP Levels Circ. Res., October 1, 2004; 95(7): 726 - 733. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Rodriguez-Sinovas, D. Garcia-Dorado, M. Ruiz-Meana, and J. Soler-Soler Enhanced effect of gap junction uncouplers on macroscopic electrical properties of reperfused myocardium J. Physiol., August 15, 2004; 559(1): 245 - 257. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Schulz and G. Heusch Connexin 43 and ischemic preconditioning Cardiovasc Res, May 1, 2004; 62(2): 335 - 344. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||
t · f). t, time; f, frequency of the injected current; I, intensity of the current; Epi, epicardial; Endo, endocardium.
