Ischemic preconditioning: infarct size is a more reliable endpoint than functional recovery.
ABSTRACT The search for the mechanism of preconditioning-induced cardioprotection has been hampered by controversial results obtained by workers using different animal species, experimental models, protocols and endpoints. The aim of this study was to evaluate the role of the perfusion model (retrograde vs working), the infarct size and severity of ischaemia (regional vs global) as well as the endpoint (functional recovery vs infarct size) in preconditioning. The isolated perfused rat heart was preconditioned by 3 x 5 min global ischaemia, followed by different periods of regional or global ischaemia and reperfusion. Ischaemic preconditioning of working hearts resulted in increased functional recovery after 25-35 min global ischaemia, while retrogradely perfused hearts showed no significant improvement (except after 30 min global ischaemia). In addition, the percentage reduction in functional performance during reperfusion observed in the latter group was significantly less than in working hearts. Hearts were also subjected to regional ischaemia, perfused in either retrograde or working mode and infarct size determined. Regionally ischaemic working as well as retrogradely perfused hearts when preconditioned showed a significant increase in functional recovery after 35 min ischaemia only. In contrast to global ischaemia, the percentage recovery in mechanical performance of regionally ischaemic hearts was not affected by the mode of perfusion. Preconditioning of working hearts caused a significant reduction in infarct size after both 30 and 35 min ischaemia. However, preconditioned retrogradely perfused hearts showed a significant decline in infarct size after 35 min regional ischaemia only. In conclusion, the effect of the perfusion mode on functional recovery is dependent on the size and severity of ischaemia. It also affects the ischaemic time at which infarct size reduction by prior preconditioning occurs in the retrogradely perfused heart.
Article: Polyphenol (-)-epigallocatechin gallate during ischemia limits infarct size via mitochondrial K(ATP) channel activation in isolated rat hearts.[show abstract] [hide abstract]
ABSTRACT: Polyphenol (-)-epigallocatechin gallate (EGCG), the most abundant catechin of green tea, appears to attenuate myocardial ischemia/reperfusion injury. We investigated the involvement of ATP-sensitive potassium (K(ATP)) channels in EGCG-induced cardioprotection. Isolated rat hearts were subjected to 30 min of regional ischemia and 2 hr of reperfusion. EGCG was perfused for 40 min, from 10 min before to the end of index ischemia. A nonselective K(ATP) channel blocker glibenclamide (GLI) and a selective mitochondrial K(ATP) (mK(ATP)) channel blocker 5-hydroxydecanoate (HD) were perfused in EGCG-treated hearts. There were no differences in coronary flow and cardiodynamics including heart rate, left ventricular developed pressure, rate-pressure product, +dP/dt(max), and -dP/dt(min) throughout the experiments among groups. EGCG-treatment significantly reduced myocardial infarction (14.5+/-2.5% in EGCG 1 microM and 4.0+/-1.7% in EGCG 10 microM, P<0.001 vs. control 27.2+/-1.4%). This anti-infarct effect was totally abrogated by 10 microM GLI (24.6+/-1.5%, P<0.001 vs. EGCG). Similarly, 100 microM HD also aborted the anti-infarct effect of EGCG (24.1+/-1.2%, P<0.001 vs. EGCG ). These data support a role for the K(ATP) channels in EGCG-induced cardioprotection. The mK(ATP) channels play a crucial role in the cardioprotection by EGCG.Journal of Korean medical science 03/2010; 25(3):380-6. · 0.84 Impact Factor
Article: Effects of postconditioning with N,N,N'N'-tetrakis-[2-pyridylmethyl]-ethylenediamine in isolated rat hearts.[show abstract] [hide abstract]
ABSTRACT: It was reported that N,N,N'N'-tetrakis-[2-pyridylmethyl]-ethylenediamine (TPEN), a transition metal chelator, confers cardioprotection against myocardial ischemic injury. In this study, we investigated the effect of TPEN targeting reperfusion period in isolated rat hearts. Langendorff perfused rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Hearts were randomly assigned to either control (n = 9) or 10 microM of TPEN (n = 8) groups. TPEN was perfused for a period of 5 min before and 30 min after reperfusion. The ratio of infarct area/ischemic area (AN/AR) was significantly reduced in TPEN treated hearts (6.9 +/- 1.7%, P < 0.001) compared to control hearts (29.5 +/- 3.2%). Recovery of left ventricular developed pressure (LVDP), rate-pressure product (RPP), +dP/dt(max), and -dP/dt(min) in the control group after reperfusion were 53.8 +/- 6.2%, 51.0 +/- 6.3%, 51.9 +/- 5.7%, and 51.4 +/- 5.7%, respectively, of the baseline levels. In the TPEN group, LVDP, RPP, +dP/dt(max), and -dP/dt(min) returned to 58.5 +/- 4.6%, 54.8 +/- 6.4%, 61.7 +/- 4.9%, and 53.4 +/- 3.9%, respectively, of the baseline levels. There were no significant differences in the cardiodynamic variables between the two groups (P > 0.05). Pharmacological postconditioning with TPEN reduces myocardial infarction however, TPEN does not modify post-ischemic systolic dysfunction in isolated rat hearts.Korean journal of anesthesiology 03/2010; 58(3):290-5.
Article: Polyphenol (-)-epigallocatechin gallate targeting myocardial reperfusion limits infarct size and improves cardiac function.[show abstract] [hide abstract]
ABSTRACT: This experiment was performed to determine the effect of polyphenolic (-)-epigallocatechin (EGCG), the most abundant catechin of green tea, given at reperfusion period. Isolated rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Green tea extract (GT) was perfused with the following concentrations; 0, 0.5, and 1 microM (GT-O, GT-0.5, and GT-1, respectively). In a next experiment, hearts were assigned randomly to one of the following groups; Control, EGCG-1 (1 microM of EGCG), and EGCG-10 (10 microM of EGCG). GT and EGCG were perfused for a period of 5 min before and 30 min after reperfusion. For comparison of cardioprotection among groups, morphometric measurement was performed by 2,3,5-triphenyltetrazolium chloride staning. GT 1 microM (10.3 +/- 2.1%, P < 0.05) significantly reduced infarct volume as a percentage of ischemic volume compared to untreated hearts (27.4 +/- 1.1%). EGCG 10 microM (13.2 +/- 4.0%) significantly reduced myocardial infarction compared to control hearts (27.2 +/- 1.4%, P = 0.002). After 2 h of reperfusion, cardiodynamic variables, including left ventricular developed pressure, rate-pressure produce, +dP/dt(max), and -dP/dt(min) were significantly improved by 10 microM of EGCG compared to control hearts (P = 0.01, 0.016, 0.009, and 0.019, respectively). EGCG treatment at an early reperfusion period reduces myocardial infarction and improves cardiodynamics in isolated rat hearts.Korean journal of anesthesiology 02/2010; 58(2):169-75.