Isolated rat ventricular myocytes retain protection afforded by in vivo hypoxic preconditioning or chronic hypoxia

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ABSTRACTS / Journal of Molecular and Cellular Cardiology 44 (2008) 711–825

of mRNA levels of type 1 IP3R — Ca2+ release channel. The changes were observed in both atria and ventricles and correlated well with contents of the IP3R1 protein. These results suggest that altered gene expression as well as posttranslational modifications of some SR Ca2+ handling proteins might affect intracellular calcium homeostasis and cardiac function during the aging process. This work was supported by grants VEGA SR 1/0027/08 and APVV 51-027404. Keywords: Aging; Sarcoplasmic reticulum; Gene expression doi:10.1016/j.yjmcc.2008.02.031

Abstract No. 31 Different modulation of type 1 and 2 IP3 receptors by stress and catecholamines Olga Krizanovaa,⁎, Silvia Pastorekovab, Richard Kvetnanskyc. a Institute of Molecular Physiology and Genetics, SAS, Vlarska 5, 833 34 Bratislava, Slovakia. bInstitute of Virology, SAS, Bratislava, Slovakia. cInstitute of Experimental Endocrinology, SAS, Bratislava, Slovakia ⁎ Corresponding author. Tel.: +421 254772211; fax: +421 254773666. E-mail address: [email protected] Inositol 1,4.5-triphosphate receptors are calcium release channels located in the endoplasmic/sarcoplasmic membrane of the cell. In the heart, both type 1 and 2 receptors are present, but differently localized. The type 1 IP3 receptors are most abundant in cardiac ganglia and type 2 IP3 receptors are prevalent in cardiomyocytes. In the heart, gene expression of type 1 IP3 receptor is modulated by catecholamines, while type 2 receptor is not affected. In this study, we compared the effect of two stressors – cold exposure and hypoxia – on the gene expression and protein levels of the type 1 and 2 IP3 receptors. We have shown that both types of IP3 receptors were increased by these stressors, although the response of the type 2 IP3 receptors was delayed. We propose that physiological importance of these types of IP3 receptors in the heart might differ in both, control conditions and during stress. This work was supported by following grants: APVT 51027404 and VEGA 2/6078. Keywords: IP3 receptors; Stress; Catecholamines doi:10.1016/j.yjmcc.2008.02.032

Portnichenko, Olexiy O. Moybenko. Bogomoletz Institute of Physiology, NAS of Ukraine, Kyiv, Ukraine. ICAMER, NAS of Ukraine, Kyiv, Ukraine ⁎ Corresponding author. 4 Bogomoletz Street, 01024 Kyiv, Ukraine. Tel.: +38 44 2562061; fax: +38 44 2562494. E-mail address: [email protected]

Earlier we established the ability of acute systemic (whole body) hypoxia to induce the phenomenon of delayed cardioprotection in rats (Portnychenko et al., 2002). This late hypoxic preconditioning led to infarct size, LDH release, and myocardial apoptosis reduction, as well as strongly prevented fatal arrhythmia incidence in ischemic and reperfused isolated hearts. Transcription factors involved were studied in adult male Wistar rats exposed to the hypoxic preconditioning (normobaric hypoxia with 10% O2 in air, 3 h, or hypobaric hypoxia in barochamber, 5600 m, 3 h). Expression of HIF-1α and HIF-3α mRNA was estimated by RTPCR, and expression of HIF-1α protein — by Western blotting. It was shown that initial HIF-3α mRNA expression was 9.0-fold higher than HIF-1α expression in both ventricles. In the right ventricles expression values were 4.0–8.0-fold higher, than in the left ones. In 24 h after the preconditioning, HIF-1α and HIF-3α mRNA expression strongly elevated (2.4–2.8-fold) in the left ventricles without HIF protein stabilization. The right ventricles demonstrated a significant increase only in HIF-3α mRNA expression (1.4-fold). Thus, the right ventricles have initial higher oxygen sensitivity and gene transcription ability (“native preconditioning”), and less reaction to hypoxical stimuli that is accompanied by more significantly delayed cardioprotection from infarction than in the left ventricles. HIF-3α seems to be more strongly involved in hypoxic preconditioning than HIF-1α. Keywords: Late hypoxic preconditioning; HIF-3α; Left and right ventricles doi:10.1016/j.yjmcc.2008.02.033

Abstract No. 33 Isolated rat ventricular myocytes retain protection afforded by in vivo hypoxic preconditioning or chronic hypoxia Gudrun H. Borchert⁎, Jan Kopecky, Frantisek Kolar. Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic. Centre for Cardiovascular Research, Prague, Czech Republic ⁎ Corresponding author. Tel.: +420 241062693; fax: +420 241062125. E-mail address: [email protected]

Abstract No. 32 Expression of HIF-1α and HIF-3α differentially changed in rat heart ventricles after hypoxic preconditioning Alla G. Portnychenko⁎, Viktor E. Dosenko, Volodymyr I.

Both hypoxic preconditioning (HP) and chronic hypoxia (CH) protect the heart against injury caused by acute oxygen deprivation. The aim of the study was to find out whether the protection was preserved in ventricular myocytes isolated after

ABSTRACTS / Journal of Molecular and Cellular Cardiology 44 (2008) 711–825

HP and CH of intact rats. Animals were exposed to normobaric hypoxia (10% O2) for 8, 24 h or 21 days followed by 24 h of normoxia. Myocytes were isolated from the left (LVM) and right (RVM) ventricles and the septum (SEPM), and subjected to 25 min of “anoxia” (metabolic inhibition) followed by 30 min of reoxygenation (A/R). Viability and LDH release were evaluated at the beginning of the experiment, after anoxia, and after reoxygenation. Neither HP nor CH affected the viability of the myocytes per se. Initial LDH (total and released) did not differ in LVM and SEPM from any hypoxic group; in contrast, CH doubled LDH in RVM. Both HP and CH increased the viability after A/R of LVM and SEPM more than twice compared to normoxic controls (HP: 80% and 83%, CH: 70% and 79%, controls: 33% and 39%, respectively). The RVM of the CH group exhibited a somewhat smaller protection (59% vs. 32% in the controls), possibly reflecting a negative influence of hypertrophy. Similar protective effects were observed when LDH release was measured just after anoxia. LDH release after A/R was significantly lower in HP groups compared to normoxic controls while protection afforded by CH was less pronounced (HP: 109%, 107% and 114%, CH: 117%, 125% and 125%, controls: 132%, 129% and 139% in LVM, SEPM and RVM, respectively). In conclusion, the protective effects of both HP and CH were retained in subsequently isolated cardiomyocytes subjected to an acute A/R protocol. Although the increase in viability was comparable, protection against irreversible A/R injury (LDH release) was somewhat greater in myocytes isolated from HP rats compared to CH animals. Supported by GA CR 305/07/0875 and 305/07/1008. Keywords: Chronic hypoxi a; Ventricula r myocy tes; LDH release doi:10.1016/j.yjmcc.2008.02.034

Abstract No. 34 Postconditioning as a trigger of preconditioning in a following prolonged ischemic insult Anastasia Zoga, Konstantinos Iliodromitis, Eftihios Prokovas, Theodora Manolaki, Theano Fotopoulou, Apostolos Papalois, Efstathios K. Iliodromitis⁎, Dimitrios Th. Kremastinos. 2nd University Department of Cardiology, Attikon Hospital, University of Athens, Greece ⁎ Corresponding author. Tel.: +30 210 5831249; fax: +30 210 5832351. E-mail address: [email protected] Preconditioning and postconditioning protect the ischemic and reperfused heart limiting the infarct size after a single episode of sustained ischemia. However, no data exist for the effectiveness of these protective mechanisms if a second episode of sustained ischemia follows the first. The aim of the present

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study is to test whether postconditioning after a prolonged ischemic insult may act as preconditioning stimulus in a subsequent second episode of sustained ischemia. In vivo New Zealand male white rabbits were divided into four groups (n = 5– 7/group) and were subjected to regional ischemia of the heart as follows: 20 min ischemia (Control A group), 20 min ischemia followed by postconditioning with 6 cycles of 10 s ischemia/ reperfusion (total time 2 min) applied at the beginning of reperfusion (PostC group), two periods of 20 min ischemia each, separated by 12 min of reperfusion (Control B group) and to postconditioning as previously described but followed by a second period of 20 min ischemia, 12 min after the first (PostCPC group). After the end of the prolonged ischemic periods all hearts were reperfused for 3 h. The infarct size was estimated as the ratio of the infarcted to risk zone in percent (%I/R). Results: %I/R was 24.2 ± 3.2 in Control A, 20.6 ± 2.2 in PostC ( p = NS), 38.1 ± 6.6 in Control B and 15.7 ± 1.9 in Post-PC ( p b 0.05 vs. Control B). We conclude that postconditioning has no effect after 20 min of ischemia but it acts as a trigger of preconditioning in a subsequent prolonged ischemic insult limiting the infarct size. Keywords: Preconditioning; Postconditioning; Protection doi:10.1016/j.yjmcc.2008.02.035

Abstract No. 35 KATP-mediated potassium effluxes in intact diabetic rat hearts Olga Jilkinaa,b,⁎, Bozena Kuzioa, Valery V. Kupriyanova,b. a Institute for Biodiagnostics, NRC, 435 Ellice Avenue, Winnipeg, Manitoba, Canada, R3B 1Y6. bUniversity of Manitoba, Winnipeg, Canada ⁎ Corresponding author. Institute for Biodiagnostics, NRC, 435 Ellice Avenue, Winnipeg, Manitoba, Canada R3B 1Y6. Tel.: +1 204 984 6558; fax: +1 204 984 7036. E-mail address: [email protected]

We investigated how metabolic changes developed during chronic (6–7 weeks) streptozotocin (STZ)-induced diabetes mellitus (DM) affect the function of cardiac sarcolemmal KATP channels. 87Rubidium (Rb+, a K+ tracer) MRS was used to assess K+ fluxes. Isolated rat hearts were loaded with Rb+ by perfusion with Krebs–Henseleit buffer (KHB) containing 50% Rb+ 50% K+. Rb+ efflux was initiated by changing perfusion to regular KHB. KATP channels were activated with 1) a mitochondrial uncoupler, DNP, that reduces [ATP]/[ADP] thus releasing inhibition of a K+-conducting subunit of the channel, Kir6.2 (metabolic effect); 2) P-1075 that interacts with the receptor subunit, SUR2A, and also produces mitochondrial uncoupling in beating rat hearts (pharmacological plus metabolic effect); and 3) in K+-arrested rat hearts, P-1075 does not cause mitochondrial uncoupling and the pure pharmacological