The aim of the study was to examine the potential role of mitochondrial permeability transition pore (mPTP) in the cardioprotective effect of chronic continuous hypoxia (CH) against acute myocardial ischemia/reperfusion (I/R) injury. Adult male Wistar rats were adapted to CH for 3 weeks, while their controls were kept under normoxic conditions. Subsequently, they were subjected to I/R insult while being administered with mPTP inhibitor, cyclosporin A (CsA). Infarct size and incidence of ischemic and reperfusion arrhythmias were determined. Our results showed that adaptation to CH as well as CsA administration reduced myocardial infarct size in comparison to the corresponding control groups. However, administration of CsA did not amplify the beneficial effect of CH, suggesting that inhibition of mPTP opening contributes to the protective character of CH.

• MeSH
• chronická nemoc MeSH
• cyklosporin * farmakologie   MeSH
• hypoxie * metabolismus   MeSH
• infarkt myokardu metabolismus   patologie   prevence a kontrola   MeSH
• krysa rodu Rattus MeSH
• potkani Wistar * MeSH
• přechodový pór mitochondriální permeability * metabolismus   MeSH
• reperfuzní poškození myokardu * metabolismus   prevence a kontrola   patologie   MeSH
• srdeční mitochondrie metabolismus   účinky léků   patologie   MeSH
• transportní proteiny mitochondriální membrány metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cyklosporin * MeSH
• přechodový pór mitochondriální permeability * MeSH
• transportní proteiny mitochondriální membrány MeSH

Adaptation to chronic hypoxia renders the heart more tolerant to ischemia/reperfusion injury. To evaluate changes in gene expression after adaptation to chronic hypoxia by RT-qPCR, it is essential to select suitable reference genes. In a chronically hypoxic rat model, no specific reference genes have been identified in the myocardium. This study aimed to select the best reference genes in the left (LV) and right (RV) ventricles of chronically hypoxic and normoxic rats. Sprague-Dawley rats were adapted to continuous normobaric hypoxia (CNH; 12% O2 or 10% O2) for 3 weeks. The expression levels of candidate genes were assessed by RT-qPCR. The stability of genes was evaluated by NormFinder, geNorm and BestKeeper algorithms. The best five reference genes in the LV were Top1, Nupl2, Rplp1, Ywhaz, Hprt1 for the milder CNH and Top1, Ywhaz, Sdha, Nupl2, Tomm22 for the stronger CNH. In the RV, the top five genes were Hprt1, Nupl2, Gapdh, Top1, Rplp1 for the milder CNH and Tomm22, Gapdh, Hprt1, Nupl2, Top1 for the stronger CNH. This study provides validation of reference genes in LV and RV of CNH rats and shows that suitable reference genes differ in the two ventricles and depend on experimental protocol.

• Klíčová slova
• Chronic hypoxia, Heart, Left ventricle, RT-qPCR, Rat, Reference genes,
• MeSH
• chronická nemoc MeSH
• hypoxie genetika   MeSH
• myokard metabolismus   patologie   MeSH
• potkani Sprague-Dawley MeSH
• referenční standardy MeSH
• regulace genové exprese * MeSH
• srdeční komory metabolismus   patologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Remodeling of the cellular distribution of gap junctions formed mainly by connexin-43 (Cx43) can be related to the increased incidence of cardiac arrhythmias. It has been shown that adaptation to chronic intermittent hypobaric hypoxia (IHH) attenuates the incidence and severity of ischemic and reperfusion ventricular arrhythmias and increases the proportion of anti-arrhythmic n-3 polyunsaturated fatty acids (n-3 PUFA) in heart phospholipids. Wistar rats were exposed to simulated IHH (7,000 m, 8-h/day, 35 exposures) and compared with normoxic controls (N). Cx43 expression, phosphorylation, localization and n-3 PUFA proportion were analyzed in left ventricular myocardium. Compared to N, IHH led to higher expression of total Cx43, its variant phosphorylated at Ser368 [p-Cx43(Ser368)], which maintains "end to end" communication, as well as p-Cx43(Ser364/365), which facilitates conductivity. By contrast, expression of non-phosphorylated Cx43 and p-Cx43(Ser278/289), attenuating intercellular communication, was lower in IHH than in N. IHH also resulted in increased expression of protein kinase A and protein kinase G while casein kinase 1 did not change compared to N. In IHH group, which exhibited reduced incidence of ischemic ventricular arrhythmias, Cx43 and p-Cx43(Ser368) were more abundant at "end to end" gap junctions than in N group and this difference was preserved after acute regional ischemia (10 min). We further confirmed higher n-3 PUFA proportion in heart phospholipids after adaptation to IHH, which was even further increased by ischemia. Our results suggest that adaptation to IHH alters expression, phosphorylation and distribution of Cx43 as well as cardioprotective n-3PUFA proportion suggesting that the anti-arrhythmic phenotype elicited by IHH can be at least partly related to the stabilization of the "end to end" conductivity between cardiomyocytes during brief ischemia.

• Klíčová slova
• arrhythmia, brief ischemia, chronic hypoxia, connexin-43, heart, n-3 PUFA,
• Publikační typ
• časopisecké články MeSH

Chronic hypoxia protects the heart against injury caused by acute oxygen deprivation, but its salutary mechanism is poorly understood. The aim was to find out whether cardiomyocytes isolated from chronically hypoxic hearts retain the improved resistance to injury and whether the mitochondrial large-conductance Ca2+-activated K+ (BKCa) channels contribute to the protective effect. Adult male rats were adapted to continuous normobaric hypoxia (inspired O2 fraction 0.10) for 3 wk or kept at room air (normoxic controls). Myocytes, isolated separately from the left ventricle (LVM), septum (SEPM), and right ventricle, were exposed to 25-min metabolic inhibition with sodium cyanide, followed by 30-min reenergization (MI/R). Some LVM were treated with either 30 μM NS-1619 (BKCa opener), or 2 μM paxilline (BKCa blocker), starting 25 min before metabolic inhibition. Cell injury was detected by Trypan blue exclusion and lactate dehydrogenase (LDH) release. Chronic hypoxia doubled the number of rod-shaped LVM and SEPM surviving the MI/R insult and reduced LDH release. While NS-1619 protected cells from normoxic rats, it had no additive salutary effect in the hypoxic group. Paxilline attenuated the improved resistance of cells from hypoxic animals without affecting normoxic controls; it also abolished the protective effect of NS-1619 on LDH release in the normoxic group. While chronic hypoxia did not affect protein abundance of the BKCa channel regulatory β1-subunit, it markedly decreased its glycosylation level. It is concluded that ventricular myocytes isolated from chronically hypoxic rats retain the improved resistance against injury caused by MI/R. Activation of the mitochondrial BKCa channel likely contributes to this protective effect.

• MeSH
• benzimidazoly farmakologie   MeSH
• blokátory draslíkových kanálů farmakologie   MeSH
• chronická nemoc MeSH
• glykosylace MeSH
• hypoxie patofyziologie   MeSH
• indoly farmakologie   MeSH
• ischemické přivykání MeSH
• kardiomyocyty účinky léků   fyziologie   MeSH
• krysa rodu Rattus MeSH
• kultivované buňky MeSH
• L-laktátdehydrogenasa metabolismus   MeSH
• potkani Wistar MeSH
• reperfuzní poškození myokardu patofyziologie   prevence a kontrola   MeSH
• separace buněk MeSH
• srdeční mitochondrie účinky léků   fyziologie   MeSH
• vápníkem aktivované draslíkové kanály s vysokou vodivostí - beta-podjednotky fyziologie   MeSH
• vápníkem aktivované draslíkové kanály s vysokou vodivostí antagonisté a inhibitory   fyziologie   MeSH
• viabilita buněk MeSH
• western blotting MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• benzimidazoly MeSH
• blokátory draslíkových kanálů MeSH
• indoly MeSH
• L-laktátdehydrogenasa MeSH
• NS 1619 MeSH Prohlížeč
• paxilline MeSH Prohlížeč
• vápníkem aktivované draslíkové kanály s vysokou vodivostí - beta-podjednotky MeSH
• vápníkem aktivované draslíkové kanály s vysokou vodivostí MeSH