Ischemic preconditioning (IP) protects the heart against subsequent prolonged ischemia. Whether the β-adrenoceptor/adenylate cyclase pathway contributes to this cardioprotection is not yet fully known. Using enzyme catalytic cytochemistry we studied the adenylate cyclase activity and its distribution in the preconditioned rat heart. Adenylate cyclase activity was examined in Langendorff-perfused rat hearts subjected to the following conditions: control perfusion; 30 min regional ischemia; 5 min occlusion and 10 min reperfusion (IP); IP followed by ischemia. Ischemia-induced arrhythmias and the effect of ischemic preconditioning on the incidence of arrhythmias were analyzed. At the end of experiment the heart was shortly prefixed with glutaraldehyde. Tissue samples from the left ventricle were incubated in a medium containing the specific substate AMP-PNP for adenylate cyclase and then routinely processed for electron microscopy. Adenylate cyclase activity was cytochemically demonstrated in the sarcolemma and the junctional sarcoplasmic reliculum (JSR) in control hearts, while it was absent after test ischemia. The highest activity of the precipitate was observed after ischemic preconditioning. In the preconditioned hearts followed by test ischemia, adenylate cyclase activity in the precipitate was preserved in sarcolemma and even more in JSR. Protective effect of ischemic preconditioning was manifested by the suppression of severe arrhythmias. These rresults indicate the involvement of the adenylate cyclase system in mechanisms underlying ischemic preconditioning., Ľ. Okruhlicová, T. Ravingerová, D. Pancza, N. Tribulová, J. Styk, R. Štetka., and Obsahuje bibliografii
Although both lipophilic and more hydrophilic statins share the same pathway of the inhibition of HMG-CoA reductase, their pleiotropic cardioprotective effects associated with the ability to cross cellular membranes, including membranes of heart cells, may differ. To test this hypothesis, isolated rat hearts were Langendorff-perfused either with simvastatin (S, 10 μ mol/l) or pravastatin (P, 30 μ mol/l), 15 min prior to ischemia. Control untreated hearts (C) were perfused with perfusion medium only. Postischemic contractile dysfunction, reperfusion-induced ventricular arrhythmias and infarct size were investigated after exposure of the hearts to 30- min global isch emia and 2-h reperfusion. Both lipophilic S and hydrophilic P reduced the severity of ventricular arrhythmias (arrhythmia score) from 4.3±0.2 in C to 3.0±0 and 2.7±0.2 in S and P, respectively, (both P<0.05), decreased the duration of ventricular tachycardia and suppressed ventricular fibrillation. Likewise, the extent of lethal injury (infarct size) determined by tetrazolium staining and expressed in percentage of risk area, was significantly lower in both treated groups, moreover, the effect of P was more pronounced (27±2 % and 10±2 % in S and P groups, respectively, vs. 42±1 % in C; P<0.05). In contrast, only S, but not P, was able to improve postischemic recovery of left ventricular developed pressure (LVDP; 48±12 % of preischemic values vs. 25±4 % in C and 21± 7 % in P groups; P<0.05). Our results suggest that differences in water solubility of statins indicating a different ability to cross cardiac membranes may underlie their distinct cardioprot ective effects on myocardial stunning and lethal injury induced by ischemia/reperfusion., S. Čarnická ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
a1_Ischemic preconditioning (I-PC) induced by brief episodes of ischemia and reperfusion (I/R) protects the heart against sustained I/R. Although activation of mitochondrial K ATP channels (mitoK ATP) interacting with reactive oxygen species (ROS) has been proposed as a key event in this process, their role in the antiarrhythmic effect is not clear. This study was designed: 1) to investigate the involvement of mito K ATP opening in the effect of I-PC (1 cycle of I/R, 5 min each) on ventricular arrhythmias during test ischemia (TI, 30-min LAD coronary artery occlusion) in Langendorff-perfused rat hearts and subsequent postischemic contractile dysfunction, and 2) to characterize potential mechanisms of protection confer red by I-PC and pharmacological PC induced by mito K ATP opener diazoxide (DZX), with particular regards to the modulation of ROS generation. Lipid peroxidation (an indicator of increased ROS production) was determined by measurement of myocardial concentration of conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in non-ischemic controls, non-preconditi oned and preconditioned hearts exposed to TI, I-PC alone, as well as after pretreatment with DZX, mito K ATP blocker 5-hydroxydecanoate (5-HD) and antioxidant N-acetylcysteine (NAC)., a2_Total number of ventricular premature beats (VPB) that occurred in the control hearts (518±71) was significantly (P<0.05) reduced by I-PC (195±40), NAC (290±56) and DZX (168±22). I-PC and NAC suppressed an increase in CD and TBARS caused by ischemia indicating lower production of ROS. On the other hand, I-PC and DZX themselves moderately enhanced ROS generation, prior to TI. Bracketing of I-PC with 5-HD suppressed both, ROS production during PC and its cardioprotective effect. In conclusion, potential mechanisms of protection conferred by mito K ATP opening in the rat heart might involve a temporal increase in ROS production in the preconditioning phase triggering changes in the pro/antioxidant balance in the myocardium and attenuating ROS production during subsequent prolonged ischemia., J. Matejíková ... [et al.]., and Obsahuje seznam literatury
We examined the involvement of phosphatidylinositol 3-kinase (PI3K) and its effector protein ki nase B (Akt) in cardioprotective effects of ischemic preconditioning (PC) with particular regards to its role in the protection against ischemia-induced arrhythmias in isolated perfused rat heart. PI3K/Akt inhibitor wortmannin (100 nM) was administered 15 min prior to 30-min regional (left anterior descending coronary artery occlusion) ischemia for the study of ischemic arrhythmias in the hearts perfused at constant coronary flow or prior to 30-min global ischemia followed by 2-h reperfusion for the infarct size (IS) determination (tetrazolium staining) in the hearts perfused at constant pressure. PC procedure (one cycle of isch emia/reperfusion, 5 min each) significantly reduced the total number of ventricular premature complexes (PVC) and severity of arrhythmias (arrhythmia score; AS) over the whole period of left anterior descending coronary artery occlusion in comparison with non-PC controls (PVC 166±40; AS 1.6±0.2 vs . 550±60 and 3.2±0.2; respectively; P<0.05). In a setting of global ischemia/reperfusion, PC decreased IS (in % of the left ventricle, LV) by 73 %. Pretreatment with wortmannin modified neither arrhythmogenesis nor IS in the non-PC hearts. Bracketing of PC with wortmannin did not abolish antiarrhythmic protection (PVC 92±25; AS 1.7±0.2; P<0.05 vs . non-PC hearts). On the other hand, wortmannin increased IS/LV in the PC hearts to 24±1.2 % as compared with 9 ± 0.6 % in the untreated ones (P<0.05). In conclusion, PI3K/Akt inhibition did not affect reduced arrhythmogenesis during ischemia in the PC hearts indicating that in contrast to its positive role in the irreversible myocardial injury, PI3K/Akt activity is not required for protection induced by PC against ischemic arrhythmias in the rat heart., T. Ravingerová, J. Matejíková, D. Pancza, F. Kolář., and Obsahuje bibliografii
The aim of our study was to characterize resistance to ischemia/reperfusion (I/R) injury in Langendorff-perfused rat hearts and effectivity of ischemic preconditioning (PC) under condition of simulated acute hyperglycemia (SAHG) by perfusion of the hearts with Krebs-Henseleit (KH) solution with elevated glucose concentration (22 mmol/l). I/R injury was induced by 30- min coronary occlusion followed by 120-min reperfusion and PC by two cycles of 5-min occlusion/5-min reperfusion, prior to I/R. The severity of I/R injury was characterized by determination of the size of infarction (IS, expressed in % of area at risk size) and the amount of heart-type fatty acid binding protein (h-FABP, a marker of cell injury) released from the hearts to the effluent. Significantly smaller IS (8.8±1 %) and lower total amount of released h-FABP (1808±660 pmol) in PC group compared with IS 17.1±1.2 % (p<0.01) and amount of h-FABP (8803±2415 pmol, p<0.05) in the non-PC control hearts perfused with standard KH solution (glucose 11 mmol/l) confirmed protective effects of PC. In contrast, in SAHG groups, PC enhanced IS (21.4±2.2 vs. 14.3±1.3 %, p<0.05) and increased total amount of h-FABP (5541±229 vs. 3458±283 pmol, p<0.05) compared with respective non-PC controls. Results suggest that PC has negative effect on resistance of the hearts to I/R injury under conditions of elevated glucose in vitro., M. Zálešák, P. Blažíček, D. Pancza, V. Ledvényiová, M. Barteková, M. Nemčeková, S. Čarnická, A. Ziegelhöffer, T. Ravingerová., and Obsahuje bibliografii
a1_Statins, the inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are most frequently used drugs in the prevention of coronary artery disease due to their cholesterol- lowering activity. However, it is not exactly known whether these effects of statins or those independent of cholesterol decrease account for the protection ag ainst myocardial ischemia- reperfusion (I/R) injury. In this study, we investigated the effect of 5-day treatment with simvastatin (10 mg/kg) in Langendorff- perfused hearts of healthy control (C) and diabetic- hypercholesterolemic (D-H; strept ozotocin + high fat-cholesterol diet, 5 days) rats subjected to 30-min global ischemia followed by 40-min reperfusion for the examination of postischemic contractile dysfunction and reperfusion-induced ventricular arrhythmias or to 30-min (left anterior descending) coronary artery occlusion and 2-h reperfusion for the infarct size determination (IS; tetrazolium stai ning). Postischemic recovery of left ventricular developed pressu re (LVDP) in animals with D-H was improved by simvastatin therapy (62.7±18.2 % of preischemic values vs. 30.3±5.7 % in the untreated D-H; P<0.05), similar to the values in the simvastatin-treated C group, which were 2.5-fold higher than those in the untreated C group. No ventricular fibrillation occurred in the simvastatin-treated C and D-H animals during reperf usion. Likewise, simvastatin shortened the duration of ventri cular tachycardia (10.2±8.1 s and 57.8±29.3 s in C and D-H vs. 143.6±28.6 s and 159.3±44.3 s in untreated C and D-H, respectively, both P<0.05). The decreased arrhythmogenesis in the simvastatin-treated groups correlated with the limitation of IS (in % of risk area) by 66 % and 62 % in C and D-H groups, respectively. However, simvastatin treatment decreased plasma cholesterol levels neither in the D-H animals nor in C., a2_The results indicate that other effects of statins (independent of cholesterol lowering) are involved in the improvement of contractile recovery and attenuation of lethal I/R injury in both, healthy and diseased individuals., A. Adameová, A. Harčárová, J. Matejíková, D. Pancza, M. Kuželová, S. Čarnická, P. Švec, M. Barteková, J. Styk, T. Ravingerová., and Obsahuje bibliografii
Diabetic heart is suggested to exhibit either increased or decreased resistance to ischemic injury. Ischemic preconditioning suppresses arrhythmias in the normal heart, whereas relatively little is known about its effects in the diseased myocardium. Our objective was to investigate whether development of diabetes mellitus modifies the susceptibility to ischemia-induced arrhythmias and affects preconditioning in the rat heart. Following 1 and 9 weeks of streptozotocin-induced (45 mg/kg, i.v.) diabetes, the hearts were Langendorff-perfused at constant pressure of 70 mm Hg and subjected to test ischemia induced by 30 min occlusion of the left anterior descending (LAD) coronary artery. Preconditioning consisted of one cycle of 5 min ischemia and 10 min reperfusion, prior to test ischemia. Susceptibility to ischemia-induced arrhythmias was lower in 1-week diabetics: only 42 % of diabetic hearts exhibited ventricular tachycardia (VT) and 16 % had short episodes of ventricular fibrillation (VF) as compared to VT 100 % and VF 70 % (including sustained VF 36 %) in the non-diabetics (P<0.05). Development of the disease was associated with an increased incidence of VT (VT 92 %, not significantly different from non-diabetics) and longer total duration of VT and VF at 9-weeks, as compared to 1-week diabetics. Preconditioning effectively suppressed arrhythmias in the normal hearts (VT 33 %, VF 0 %). However, it did not provide any additional antiarrhythmic protection in the acute diabetes. On the other hand, in the preconditioned 9-weeks diabetic hearts, the incidence of arrhythmias tended to decrease (VT 50 %, transient VF 10 %) and their severity was reduced. Diabetic rat hearts are thus less susceptible to ischemia-induced arrhythmias in the acute phase of the disease. Development of diabetes attenuates increased ischemic tolerance, however, diabetic hearts in the chronic phase can benefit more from ischem preconditioning, due to its persisting influence., T. Ravingerová, R. Štetka, D. Pancza, O. Uličná, A. Ziegelhöffer, J. Styk., and Obsahuje bibliografii
Contrary to clinical trials, experimental studies revealed that diabetes mellitus (DM) may initiate, besides increased myocardial vulnerability to ischemia-reperfusion injury (I/R) and pro/antioxidant dysbalance, development of adaptation leading to an enhanced tolerance to I/R. The aims were to characterize 1) susceptibility to ischemia-induced ventricular arrhythmias in the diabetic rat heart 2) its response to antioxidant N-acetylcysteine (NAC ) and a NOS inhibitor L-NAME, and 3) the effect of DM on endogenous antioxidant systems. Seven days after streptozotocin injection (65 mg/kg, i.p.), Langendorff-perfused control (C) and DM hearts were subjected to 30-min occlusion of the LAD coronary artery with or without prior 15-min treatment with L-NAME (100 μM) or NAC (4 mM). Total number of ventricular premature beats (VPB), as well the total duration of ventricular tachycardia (VT) were reduced in the DM group (from 533±58 and 37.9±10.2 s to 224.3±52.6 and 19±13.5 s; P<0.05). In contrast to the antiarrhythmic effects of L-NAME and NAC in controls group (VPB 290±56 and 74±36, respectively; P<0.01 vs. control hearts), application of both drugs in the diabetics did not modify arrhythmogenesis (L-NAME: VPB 345±136, VT 25±13 s; NAC: VPB 207±50, VT 12±3.9 s; P>0.05 vs non-treated diabetic hearts). Diabetic state was associated with significantly elevated levels of CoQ 10 and CoQ 9 (19.6±0.8 and 217.3±9.5 vs. 17.4± 0. 5 and 185.0±5.0 nmol/g, respectively, in controls; P<0.05), as well as α-tocopherol (38.6±0.7 vs. 31.5±2.1 nmol/g in controls; P<0.01) in the myocardial tissue. It is concluded that early period of DM is associated with enhanced resistance to ischemia-induced arrhythmias. Diabetes mellitus might induce adaptive processes in the myocardium leading to lower susceptibility to antioxidant and L-NAME treatment., J. Matejíková, J. Kucharská, D. Pancza, T. Ravingerová., and Obsahuje bibliografii a bibliografické odkazy