| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Departments of 1Physiology II and 2Thoracic-Cardiovascular Surgery, Nara Medical University, Kashihara, Nara; and 3Department of Neurology and Neurosurgery, Kanazawa Medical University, Kahoku-gun, Ishikawa, Japan
Submitted 6 July 2004 ; accepted in final form 31 October 2004
 |
ABSTRACT |
|---|
 TOP ABSTRACT METHODSRESULTSDISCUSSIONREFERENCES |
|---|
-fodrin. To test this hypothesis, we investigated the effect of calpain inhibitor-1 on LV mechanical work and energetics in the cross-circulated rat hearts that underwent 15-min global ischemia and 60-min reperfusion (n = 9). After ischemia-reperfusion with calpain inhibitor-1, mean end-systolic pressure at midrange LV volume and systolic pressure-volume area (PVA) at midrange LV volume (total mechanical energy per beat) were hardly changed, although they were significantly (P < 0.01) decreased after ischemia-reperfusion without calpain inhibitor-1. Mean myocardial oxygen consumption per beat (VO2) intercepts (PVA-independent VO2; VO2 for the total Ca2+ handling in excitation-contraction coupling and basal metabolism) of VO2-PVA linear relations were also unchanged after ischemia-reperfusion with calpain inhibitor-1, although they were significantly (P < 0.01) decreased after ischemia-reperfusion without calpain inhibitor-1. There were no significant differences in O2 costs of LV PVA and contractility among the hearts in control (or normal) postischemia-reperfusion and postischemia-reperfusion with calpain inhibitor-1. Western blot analysis of -fodrin and the immunostaining of 150-kDa products of -fodrin confirmed that calpain inhibitor-1 almost completely protected the proteolysis of -fodrin. Our results indicate that calpain inhibitor-1 prevents the heart from ischemia-reperfusion injury associated with the impairment of total Ca2+ handling by directly inhibiting the proteolysis of -fodrin.
cardiac function; systolic pressure-volume area; oxygen consumption; -fodrin
-fodrin by blocking Ca2+ overload and consequent activation of calpain, a neutral protease. Activation of calpain results in the proteolysis of several cellular proteins associated mostly with the cellular membrane, including cytoskeleton proteins (e.g., spectrin, fodrin, and microtubule-associated proteins), membrane proteins, enzymes, cytokines, and transcription factors. Although many of these might be implicated in mechanisms contributing to I/R injury, the exact role of calpain activation in postischemia tissues has not been clearly defined (22).
We have previously reported that high Ca2+ intracoronary infusion causes Ca2+ overload-induced cardiac dysfunction and that a calpain inhibitor protects the formation of such acute failing hearts. Proteolysis of cytoskeleton protein -fodrin was found in these acute failing hearts without proteolysis of ankyrin, connexin43, and troponin I and was inhibited by a calpain inhibitor (32, 36). Although mechanisms other than Ca2+ overload also contribute to I/R injury (2, 5, 7, 25, 34), a calpain inhibitor could protect the heart against I/R injury. We hypothesized that calpain inhibitor-1 (CI) protected left ventricular (LV) function from I/R injury by inhibiting the proteolysis of -fodrin.
To test this hypothesis, we investigated the effect of CI on LV mechanical work and energetics in the cross-circulated rat heart preparations that underwent 15-min global ischemia and 60-min reperfusion. We evaluated LV function using 1) LV end-systolic pressure-volume relation (ESPVR), 2) linear relation of myocardial oxygen consumption per beat (VO2) and systolic pressure-volume area (PVA, total mechanical energy per beat), and 3) O2 cost of equivalent maximal elastance (eEmax; an index for contractility) for Ca2+. Mean VO2 intercept [PVA-independent VO2; VO2 for the total Ca2+ handling in the excitation-contraction (E-C) coupling and basal metabolism] of VO2-PVA linear relationships significantly (P < 0.01) decreased after I/R with unchanged mean slope, whereas the mean VO2 intercept did not decrease after CI and I/R with the unchanged mean slope. The Western blot analysis and immunohistochemical staining of -fodrin and its proteolytic products revealed that CI protected proteolysis of -fodrin. Our results indicate that total Ca2+ handling in the E-C coupling is impaired after I/R, whereas treatment with CI prevents cardiac dysfunction induced by the impairment of Ca2+ handling mediated via inhibition of proteolysis of membrane -fodrin without blockade of the more energy-consuming processes, i.e., extrusion of Ca2+ mediated via forward mode NCX and Na+-K+ pump coupled to NCX (1 ATP:1 Ca2+) where energy demand is twofold of that for uptake of Ca2+ by sarco(endo)plasmic reticulum Ca2+ pump (SERCA2a) (1 ATP:2 Ca2+) (28) during the initial reperfusion.
|
METHODS |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Surgical preparation. Experiments were performed on 24 excised, cross-circulated rat heart preparations, as reported previously (10, 11, 32, 33). In each experiment, three retired breeder male crj:Wistar rats weighing 526 ± 69 g (16–25 wk of age), purchased from Charles River Japan (Yokohama, Japan), were anesthetized with pentobarbital sodium (50 mg/kg ip) and used as blood supplier and metabolic supporter rats, respectively. One Wistar rat was used as a blood supplier. All rats were heparinized (1,000 units iv). The beating heart was excised from one retired rat without interruption of coronary perfusion and supported by cross circulation with the other metabolic supporter rat as previously reported in detail (10). The excised heart was maintained at 37°C.
A thin latex balloon (balloon material volume, 0.08 ml) fitted into the LV was connected to a pressure transducer (Life Kit DX-312, Nihon Kohden, Tokyo, Japan) and a 0.5-ml precision glass syringe with fine scales (minimum scale: 0.005 ml). The maximum unstretched balloon volume was below 
0.20–0.25 ml. Thus LV volume (LVV) was changed and measured by adjusting the intraballoon water volume with the syringe in 0.05-ml steps between 0.08 and 0.23 ml.
Systolic unstressed volume (V0) was determined by filling the balloon to the level where peak isovolumic pressure and hence PVA (see Data analysis) were zero. The sum of intraballoon water volume and balloon material volume (0.08 ml) was used as an initial estimate of V0. This procedure was repeated during different LVV loading runs. V0 was then finally determined as the volume-axis intercept of the best-fit ESPVR. We obtained the best-fit ESPVR with Eq. 1 shown in Table 1 by means of the least-squares method (Delta-Graph, DeltaPoint; Monterey, CA) on a personal computer (1, 10, 11, 21, 32, 33). Correlation coefficients of the best-fit ESPVRs were higher than 0.98 (Table 1).
|
Oxygen consumption. Myocardial oxygen consumption was obtained as the product of coronary flow and coronary arteriovenous O2 content difference (AVO2D) (10, 33). Total coronary blood flow (CF) was continuously measured with an electromagnetic flowmeter (MFV-3100, Nihon Kohden, Tokyo, Japan) placed in the middle of the coronary venous drainage tubing from the right ventricle. LV thebesian flow was negligible. The coronary AVO2D was continuously measured by passing all the arterial and venous cross-circulation blood through the cuvettes of a custom-made AVO2D analyzer (PWA-200S, Shoe Technica; Chiba, Japan) as previously reported in detail (10, 33). The mean concentration of hemoglobin in the perfused blood was 14.0 ± 1.2 mg/dl.
As shown previously (1, 10, 11, 33), the VO2-PVA relationship was linear in the rat LV. Its slope represents the O2 cost of PVA, and its VO2 intercept represents the PVA-independent VO2. The PVA-independent VO2 is composed of VO2 in E-C coupling (29) and basal metabolism (21, 28). The right ventricle was kept collapsed by continuous hydrostatic drainage of the coronary venous return so that the right ventricular PVA and hence PVA-dependent VO2 were assumed to be negligible (10, 33). The right ventricular PVA-independent VO2 (10, 11, 32, 33) was subtracted from the total VO2 to yield LV VO2. The LV (including the septum) and the right ventricle were weighed for normalization of LVV. They were 1.05 ± 0.15 and 0.30 ± 0.05 g (n = 9) in the control I/R group and 1.06 ± 0.19 and 0.28 ± 0.07 g (n = 9) in the CI-treated I/R (CI + I/R) group. There were no significant differences in left and right ventricular weights between the two groups.
Experimental protocol. LV pressure (LVP), VO2, and PVA data during isovolumic contractions were simultaneously obtained at six to seven different LVVs in each rat heart (vol-run). All hearts except for six normal hearts underwent 15-min global ischemia (37°C) and 60- min reperfusion. Cardiac arrest was found after 8.0 ± 1.5 min (6–12 min) of global ischemia. At the onset of reperfusion, 3 ml of the blood remaining in the coronary circulation system during ischemia were removed from the venous return tube. After 60-min reperfusion with and without infusion of 10 µmol/l CI, the vol-runs were performed again: post-I/R and post-CI + I/R vol-runs, as shown in Fig. 1.
|
To measure basal metabolic O2 consumption, cardiac arrest was induced by infusing KCl (0.5 mol/l) into the coronary perfusion tubing at 10 ml/h (n = 3 each) that was adjusted to abolish electrical excitation under monitoring ventricular electrocardiograms but not to generate any KCl-induced constrictions of coronary vessels. VO2 and PVA data were obtained by minimal volume loading to avoid volume-loading effects, if any, on VO2 data. In each steady state, data were sampled at 500 Hz for 3 s, and sampling was usually repeated three times at intervals of 0.5–1 min.
A synthetic CI, N-acetyl-leucine-leucine-lorleucinal (ALLNoL, purchased from Chemicon), was dissolved in DMSO at 12 mmol/l and was diluted to 600 µmol/l in 5% DMSO. We adjusted the blood concentration of CI at 10 µmol/l by changing the infusion rate (1.2–5.8 ml/h) under monitoring the real-time CF. Intracoronary infusion of CI was started 1 min before ischemia and continued for 60–120 min during reperfusion (n = 9) (Fig. 1). DMSO at 0.1% had no significant effect on cardiac function or on the proteolysis of -fodrin.
Data analysis. We attempted to fit experimentally obtained LV pressure-volume data to the exponential equations to obtain ESPVRs (see Table 1) and end-diastolic pressure-volume relationships (EDPVRs) and thus determine PVA by the same method as described previously in detail (10, 11, 32, 33). On the basis of our previous proposal (10, 11, 16, 27, 33), we obtained control ESPVR and calculated end-systolic pressure at mLVV (ESPmLVV) and PVA mLVV (PVAmLVV) to assess LV mechanical work and energetics in the two groups. Mean values for mLVV and V0 (normalized for LV 1 g) were 0.15 ± 0.03 and 0.08 ± 0.01 ml/g, respectively (n = 24).
Oxygen cost of LV contractility. We obtained the specific best-fit curves for the observed ESPmLVV and ESP (0 mmHg at V0) with ESPVR function in the control vol-run by the least-squares method, and we calculated PVAmLVV during Ca2+ infusion on a personal computer (23, 26, 32, 33). The parallelism of the VO2-PVA linear relation during Ca2+ infusion has been confirmed in normal hearts (26) and also was confirmed in the present I/R hearts (n = 3). From this parallelism, the lines including all VO2-PVA data obtained during Ca2+ infusion in steps at mLVV were drawn in parallel to the control VO2-PVA relation line, as described previously (10, 23, 26, 33). The gradually increased VO2 intercept values (PVA-independent VO2 values) of the lines proportional to the enhanced LV contractility induced by Ca2+ were obtained by this procedure.
Our recently proposed index for LV contractility (i.e., eEmax) was calculated from a triangular area equivalent to PVAmLVV (26, 33). The O2 cost of LV contractility was the slope of the relationship between PVA-independent VO2 and eEmax (26, 33).
Polyacrylamide gel electrophoresis and immunoblotting of 150-kDa and 145-kDa fragment of -fodrin (240-kDa).
We have previously reported that in high-Ca2+ infusion-induced Ca2+-overloaded contractile failure associated with the impairment of the total Ca2+ handling in the E-C coupling, proteolysis of -fodrin, a cytoskeleton protein, is found without proteolysis of ankyrin, connexin43, and troponin I (32). It seems likely that -fodrin is the most sensitive membrane protein to Ca2+ overload. To compare with this contractile failure, we focused on proteolysis of -fodrin in the present I/R-induced contractile failure because there is a close correlation between the membrane -fodrin proteolysis and the impairment of the total Ca2+ handling (the decreased VO2 intercept and unchanged slope of VO2-PVA linear relation).
LV myocardium from each heart was frozen and stored at –80°C after the mechanoenergetic studies. The frozen hearts were homogenized in sucrose-Tris-EGTA buffer. The P2 fractions (membrane fractions) (20 µg protein/lane) were subjected to SDS-PAGE by the method of Laemmli (14), followed by immunoblotting according to the method of Towbin et al. (31) with modifications (37). The blots were blocked with 5% skim milk in a buffer containing 150 mmol/l NaCl, 10 mmol/l Tris·HCl (pH 7.4), and 0.05% Tween-20 and incubated with 2,000-fold diluted antibody against anti--fodrin (Biohit, Genex) for 1 h at room temperature. An ECL Western blotting detection kit visualized the protein. The amounts of the 150-kDa fragment of -fodrin were measured with an image analyzer (Densitography AE 6900, Atto) (36). The intensity of bands was expressed in arbitrary units. The statistical difference was evaluated by ANOVA with Bonferroni's post hoc analysis.
Histochemical and immunohistochemical studies. LV myocardium from each heart was frozen rapidly in isopentane chilled in dry ice and stored at –80°C before the study. For immunohistochemistry, 5-µm serial heart sections were fixed in acetone for 10 min at 4°C, rinsed in 0.01 M phosphate-buffered saline (PBS) (pH 7.2) for 15 min, and then incubated for 30 min in blocking solution containing 2% bovine serum albumin and 5% normal goat serum, as described previously (18, 36).
All sections were incubated with mouse monoclonal antibodies against -fodrin [1:1,500 (vol/vol), Affiniti, AA6]. We also used two different rabbit polyclonal antibodies against SBDP150. SBDP150 (Y1176) antibody was made at Senju pharmaceuticals (Kobe, Japan) against the new NH2-terminal of SBDP150 (H2N-Gly-Met-Met-Pro-Arg) and diluted 1:1,000 vol/vol. SBDP150 (D1185) antibody (Cell Signaling Technology) was produced with a synthetic peptide corresponding to residues surrounding Asp1185 of human -fodrin and diluted 1:100 vol/vol. After a 30-min wash in PBS, the sections were incubated with biotinylated goat anti-rabbit IgG for m-calpain, SBDP150 (Y1176), and SBDP150 (D1185) or goat anti-mouse IgG for the other antibodies and then with fluorescein isothiocynate Avidin D.
Serial sections consecutive to those processed as described were stained with hematoxylin and eosin. Normal mouse IgG and rabbit serum, diluted to the same concentration as primary mouse and rabbit antibodies, were used for negative control. The sections were photographed with Zeiss epifluorescence microscope with an appropriate filter system.
Statistics. Comparison of paired and unpaired individual values was performed by the paired and unpaired t-test, respectively. An analysis of covariance (ANCOVA) was applied to compare the two regression lines of LV VO2 on PVA in each heart between control and postischemic vol-runs. Multiple comparisons were performed by one-way or repeated-measures ANOVA with post hoc Bonferroni's test or exceptionally Dunnett's test. A value of P < 0.05 was considered statistically significant. All data are expressed as the means ± SD.
|
RESULTS |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Figure 2 shows a representative control and post-I/R set of ESPVRs and EDPVRs and VO2-PVA relations without CI (Fig. 2, A and B) and with CI (Fig. 2, C and D). Post-I/R curvilinear ESPVR markedly shifted downward, and EDPVR slightly shifted upward (Fig. 2A). Each post-I/R PVA and VO2 value at each LVV was markedly smaller than each control value, and the post-I/R VO2-PVA linear relation shifted downward without changes in the slope (Fig. 2B). On the other hand, the post-CI + I/R set of ESPVR and EDPVR only slightly shifted downward (Fig. 2C), and the post-CI + I/R VO2-PVA linear relation hardly changed; the control and post-CI + I/R VO2-PVA relations could be superimposed; neither slope nor VO2 intercept changed (Fig. 2D).
|
|
|
|
Basal metabolic oxygen consumption did not change 60 min after reperfusion in the I/R and CI + I/R groups compared with that in the normal hearts (I/R: 31.7 ± 7.2 O2·min–1·g–1, CI + I/R: 30.2 ± 5.4 µl O2·min–1·g–1, normal hearts: 30.4 ± 10.1 µl O2·min–1·g–1). Therefore, the result indicated the decrease of VO2 intercept was due to the decrease of VO2 utilized for Ca2+ handling in E-C coupling.
Polyacrylamide gel electrophoresis and immunoblotting of the 150-kDa and 145-kDa fragment of -fodrin (240 kDa).
In the I/R group, amounts of 150- and 145-kDa fragments were significantly larger than those in normal hearts and those in CI + I/R group. There was no significant difference between the normal and the CI + I/R group (Fig. 3C). Figure 3D shows two representative sets of 240-kDa -fodrin and 150- and 145-kDa -fodrin proteolytic products in the I/R and CI + I/R group hearts compared with a normal heart. Mean percent changes in PVAmLVV and VO2 intercept contrasted with changes in the amounts of -fodrin products. Percent decreases in PVAmLVV and VO2 intercept seemed to be causally related to increases of the proteolysis of -fodrin (Fig. 3, A–C).
Time course of changes in the ratio of PVA-independent VO2 to control. On the other hand, time courses of changes in the ratio of PVA-independent VO2 to each control (=1.0) for 60 min after reperfusion in I/R and CI + I/R groups were not significantly different. Each ratio of PVA-independent VO2 at 10 and 15 min after reperfusion in the I/R group and that at 15 min after reperfusion in the CI + I/R group was significantly higher than the control, whereas the ratio of PVA-independent VO2 was unchanged during the initial reperfusion for 5 min. The more energy-consuming process was not affected by treatment with CI (Fig. 4). SD values at 10 and 15 min after reperfusion in I/R and CI + I/R groups were much larger than others, indicating that variable but transient energy-consuming processes responded to I/R and CI + I/R. The ratio of PVA-independent VO2 in the I/R group gradually decreased from the control between 20 and 60 min, whereas the ratio in the CI + I/R group did not significantly decrease from the control at any time. Finally at 60 min after reperfusion, there was a significant difference in the ratio between the I/R and CI + I/R group hearts (Fig. 4).
|
The linear relations of PVA-independent VO2 and eEmax obtained during the Ca2+ infusion in the normal, I/R, and CI + I/R group hearts could be superimposed (data not shown). Mean oxygen costs of LV eEmax (the slope of PVA-independent VO2 and eEmax relation) for Ca2 in the normal, I/R, and CI + I/R group hearts are shown in Fig. 5. There were no significant differences in oxygen costs of LV contractility among the three groups. This indicated that VO2 used for Ca2+ handling in E-C coupling per unit changes in LV contractility was unchanged among the three groups.
|
Histochemical and immunohistochemical studies.
The result of histochemical studies by hematoxylin and eosin staining and immunostaining is shown in Fig. 6. -Fodrin (240 kDa) was located at the inner cell membrane (Fig. 6, D–F), and the 150-kDa -fodrin fragment was not detected in the normal heart without any treatments (Fig. 6G). In contrast to the normal heart, the 150-kDa -fodrin fragment has markedly spread over the cytoplasm in the I/R group (Fig. 6H). In the CI + I/R group, 240-kDa -fodrin was located at the cell membrane and 150-kDa -fodrin fragment has hardly spread over the cytoplasm (Fig. 6I), although the enlargement of cardiac myocytes probably due to the swelling was identified as in I/R group (Fig. 6, C vs. B).
|
-fodrin, although it seems unlikely that CI blocked the swelling of cardiac myocytes. |
DISCUSSION |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
The present results in the I/R group hearts revealed LV contractile dysfunction associated with decreased Ca2+ handling VO2 and unchanged oxygen costs of PVA and LV contractility (28, 32), indicating the decreased total amounts of Ca2+ handled in E-C coupling with unchanged contractile efficiency, sensitivity of the contractile machinery for Ca2+, Ca2+-to-ATP ratio in total Ca2+ handling, and ATP-to-VO2 ratio in the mitochondria. Therefore, the present decreased total amount of Ca2+ handled in E-C coupling after I/R is likely to be due to a suppression of the transsarcolemmal Ca2+ influx via L-type Ca2+ channel as in high-Ca2+-induced Ca2+ overload failing hearts (32).
As shown in Fig. 4, the time course of changes in the ratio of PVA-independent VO2 to control during CI + I/R was markedly different from those during KBR + I/R (see Fig. 4 in our companion paper; Ref. 9). The ratio of PVA-independent VO2 in both I/R and CI + I/R group hearts was maximally and significantly increased 15 min after reperfusion from the control, indicating that CI did not block the more energy-consuming processes. However, the ratio of PVA-independent VO2 in the I/R group hearts gradually decreased between 20 and 60 min to below the control level, whereas the ratio was unchanged in the CI + I/R group hearts. CI per se did not affect PVA-independent VO2 and thus treatment with CI antagonized the decrease of PVA-independent VO2 after I/R.
Changes in PVA-independent VO2 correspond to changes in VO2 for total Ca2+ handling, because basal metabolism was constant among normal, I/R, and CI + I/R group hearts. The increase in VO2 for total Ca2+ handling after I/R seems to result from transsarcolemmal forward-mode NCX and Na+-K+-ATPase coupled to NCX (9, 13, 24, 30), because these ionic pump and exchangers consume twofold energy of SERCA2a that has a key role in the total Ca2+ handling in normal rat hearts (3, 17, 20, 28, 29). The extremely large SD at 10 and 15 min after I/R reflects the largely varied balance between SERCA2a and forward-mode NCX plus Na+-K+-ATPase coupled to NCX in each heart. These Ca2+-extruding mechanisms fail to respond sufficiently to the increased cytosolic Ca2+ concentration, resulting in the transient Ca2+ overload and thus proteolysis of membrane -fodrin by a Ca2+-dependent protease, calpain activated by the transient Ca2+ overload (2, 12).
CI directly blocked the activation of calpain and prevented the heart against the proteolysis of -fodrin, although CI may not protect the heart from other I/R injury. It has been proposed that fodrin maintains the integrity of the plasma membranes as a constituent of the membrane skeleton (4, 15). Therefore, it seems likely that the degradation of fodrin in membrane fractions would alter the properties of ion channels (36). The present results showing decreased Ca2+ handling VO2 in E-C coupling with unchanged oxygen costs of PVA and LV contractility probably reflect the decreased total amount of Ca2+ handled, which may be due to a suppression of the transsarcolemmal Ca2+ influx. The possibility that disruption of cytoskeletal proteins inactivate L-type Ca2+ channels has been reported (8, 19). We speculate that the linkage of the L-type Ca2+ channel to the membrane fodrin acts to tether the channel in place, which somehow modulates the basal activity of the channel, and a loss of the linkage may impair its regulation. Therefore, CI did not induce any conformational changes of the L-type Ca2+ channel at the cell membrane (8, 19), resulting in protection of LV function associated with no impairment of the L-type Ca2+ channel function.
CI almost completely blocked the proteolysis of 240-kDa -fodrin but did not block the enlargement of cardiac myocytes probably due to swelling caused by I/R injury. However, CI more completely blocked LV contractile failure rather than KBR. Therefore, CI may have other beneficial effects than inhibition of calpain activity (12).
Calpains are ubiquitous neutral cysteine proteases. Although their physiological role has not been completely clarified yet, calpains seem to be involved in the expression of cell adhesion molecules. Ikeda et al. (12) recently have reported that another selective calpain inhibitor (Z-Leu-Leu-CHO) significantly reduced polymorphonuclear leukocyte-induced myocardial I/R injury by inhibiting the expression of P-selectin. Therefore, this mechanism may partially contribute to the beneficial effects in the present study.
Although we did not confirm exactly how long Ca2+ overload after I/R activated calpain, Ca2+ overload appeared to be initiated for 5 min (24, 36) and persist for another 10 min after I/R according to the present study (see Fig. 4) and the companion paper by Hagihara et al. (9). However, we performed CI infusion throughout the experiment not to activate calpain, if any, because CI per se does not have any negative inotropic actions.
We concluded that calpain inhibitor protected the heart against I/R injury associated with blockade of the proteolysis of -fodrin and with the resultant blockade of the impairment of total Ca2+ handling in excitation-contraction coupling in the blood-perfused rat heart preparation, although it did not block the more energy-consuming process during 15-min reperfusion.
The present calpain inhibitor may not be effective to prevent lethal arrhythmia during I/R, because it cannot prevent energy-consuming processes to be activated and Ca2+ overload in cardiac myocytes in contrast to the Na+/Ca2+ exchanger inhibitor KBR. On the other hand, several calpain inhibitors have been reported to reduce systemic I/R injury in the brain, liver, and kidney (6, 15, 35). Therefore, as a beneficial medicine to reduce systemic I/R injury, some calpain inhibitors, including the present one, would be promising.
|
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 |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  J. P. French, K. L. Hamilton, J. C. Quindry, Y. Lee, P. A. Upchurch, and S. K. Powers Exercise-induced protection against myocardial apoptosis and necrosis: MnSOD, calcium-handling proteins, and calpain FASEB J, August 1, 2008; 22(8): 2862 - 2871. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Jung, A. S. Martins, E. Niggli, and N. Shirokova Dystrophic cardiomyopathy: amplification of cellular damage by Ca2+ signalling and reactive oxygen species-generating pathways Cardiovasc Res, March 1, 2008; 77(4): 766 - 773. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. P. French, J. C. Quindry, D. J. Falk, J. L. Staib, Y. Lee, K. K. W. Wang, and S. K. Powers Ischemia-reperfusion-induced calpain activation and SERCA2a degradation are attenuated by exercise training and calpain inhibition Am J Physiol Heart Circ Physiol, January 1, 2006; 290(1): H128 - H136. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Nakajima-Takenaka, S. Sakata, S. Kato, Y. Ohga, K.-y. Murata, S. Taniguchi, and M. Takaki Detrimental effects after dobutamine infusion on rat left ventricular function: mechanical work and energetics Exp Physiol, July 1, 2005; 90(4): 635 - 644. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
P < 0.05 vs. I/R.
