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Garrott K, Kuzmiak-Glancy S, Wengrowski A, Zhang H, Rogers J, Kay MW. K ATP channel inhibition blunts electromechanical decline during hypoxia in left ventricular working rabbit hearts. J Physiol 2017; 595:3799-3813. [PMID: 28177123 DOI: 10.1113/jp273873] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 02/01/2017] [Indexed: 12/25/2022] Open
Abstract
KEY POINTS Heart function is critically dependent upon the balance of energy production and utilization. Sarcolemmal ATP-sensitive potassium channels (KATP channels) in cardiac myocytes adjust contractile function to compensate for the level of available energy. Understanding the activation of KATP channels in working myocardium during high-stress situations is crucial to the treatment of cardiovascular disease, especially ischaemic heart disease. Using a new optical mapping approach, we measured action potentials from the surface of excised contracting rabbit hearts to assess when sarcolemmal KATP channels were activated during physiologically relevant workloads and during gradual reductions in myocardial oxygenation. We demonstrate that left ventricular pressure is closely linked to KATP channel activation and that KATP channel inhibition with a low concentration of tolbutamide prevents electromechanical decline when oxygen availability is reduced. As a result, KATP channel inhibition probably exacerbates a mismatch between energy demand and energy production when myocardial oxygenation is low. ABSTRACT Sarcolemmal ATP-sensitive potassium channel (KATP channel) activation in isolated cells is generally understood, although the relationship between myocardial oxygenation and KATP activation in excised working rabbit hearts remains unknown. We optically mapped action potentials (APs) in excised rabbit hearts to test the hypothesis that hypoxic changes would be more severe in left ventricular (LV) working hearts (LWHs) than Langendorff (LANG) perfused hearts. We further hypothesized that KATP inhibition would prevent those changes. Optical APs were mapped when measuring LV developed pressure (LVDP), coronary flow rate and oxygen consumption in LANG and LWHs. Hearts were paced to increase workload and perfusate was deoxygenated to study the effects of myocardial hypoxia. A subset of hearts was perfused with 1 μm tolbutamide (TOLB) to identify the level of AP duration (APD) shortening attributed to KATP channel activation. During sinus rhythm, APD was shorter in LWHs compared to LANG hearts. APD in both LWHs and LANG hearts dropped steadily during deoxygenation. With TOLB, APDs in LWHs were longer at all workloads and APD reductions during deoxygenation were blunted in both LWHs and LANG hearts. At 50% perfusate oxygenation, APD and LVDP were significantly higher in LWHs perfused with TOLB (199 ± 16 ms; 92 ± 5.3 mmHg) than in LWHs without TOLB (109 ± 14 ms, P = 0.005; 65 ± 6.5 mmHg, P = 0.01). Our results indicate that KATP channels are activated to a greater extent in perfused hearts when the LV performs pressure-volume work. The results of the present study demonstrate the critical role of KATP channels in modulating myocardial function over a wide range of physiological conditions.
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Affiliation(s)
- Kara Garrott
- Department of Biomedical Engineering, The George Washington University, Washington, DC, USA
| | - Sarah Kuzmiak-Glancy
- Department of Biomedical Engineering, The George Washington University, Washington, DC, USA
| | - Anastasia Wengrowski
- Department of Biomedical Engineering, The George Washington University, Washington, DC, USA
| | - Hanyu Zhang
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jack Rogers
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, Washington, DC, USA
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Abstract
KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.
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Affiliation(s)
- Monique N Foster
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - William A Coetzee
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
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Samokhvalov V, Alsaleh N, El-Sikhry HE, Jamieson KL, Chen CB, Lopaschuk DG, Carter C, Light PE, Manne R, Falck JR, Seubert JM. Epoxyeicosatrienoic acids protect cardiac cells during starvation by modulating an autophagic response. Cell Death Dis 2013; 4:e885. [PMID: 24157879 PMCID: PMC3920965 DOI: 10.1038/cddis.2013.418] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 09/21/2013] [Accepted: 09/26/2013] [Indexed: 12/25/2022]
Abstract
Epoxyeicosatrienoic acids (EETs) are cytochrome P450 epoxygenase metabolites of arachidonic acid involved in regulating pathways promoting cellular protection. We have previously shown that EETs trigger a protective response limiting mitochondrial dysfunction and reducing cellular death. Considering it is unknown how EETs regulate cell death processes, the major focus of the current study was to investigate their role in the autophagic response of HL-1 cells and neonatal cardiomyocytes (NCMs) during starvation. We employed a dual-acting synthetic analog UA-8 (13-(3-propylureido)tridec-8-enoic acid), possessing both EET-mimetic and soluble epoxide hydrolase (sEH) inhibitory properties, or 14,15-EET as model EET molecules. We demonstrated that EETs significantly improved viability and recovery of starved cardiac cells, whereas they lowered cellular stress responses such as caspase-3 and proteasome activities. Furthermore, treatment with EETs resulted in preservation of mitochondrial functional activity in starved cells. The protective effects of EETs were abolished by autophagy-related gene 7 (Atg7) short hairpin RNA (shRNA) or pharmacological inhibition of autophagy. Mechanistic evidence demonstrated that sarcolemmal ATP-sensitive potassium channels (pmKATP) and enhanced activation of AMP-activated protein kinase (AMPK) played a crucial role in the EET-mediated effect. Our data suggest that the protective effects of EETs involve regulating the autophagic response, which results in a healthier pool of mitochondria in the starved cardiac cells, thereby representing a novel mechanism of promoting survival of cardiac cells. Thus, we provide new evidence highlighting a central role of the autophagic response in linking EETs with promoting cell survival during deep metabolic stress such as starvation.
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Affiliation(s)
- V Samokhvalov
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
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Ke Q, Xiao YF, Bradbury JA, Graves JP, Degraff LM, Seubert JM, Zeldin DC. Electrophysiological properties of cardiomyocytes isolated from CYP2J2 transgenic mice. Mol Pharmacol 2007; 72:1063-73. [PMID: 17652182 PMCID: PMC2243182 DOI: 10.1124/mol.107.035881] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
CYP2J2 is abundant in cardiac tissue and active in the biosynthesis of eicosanoids such as epoxyeicosatrienoic acids (EETs). To determine the effects of CYP2J2 and its eicosanoid products in the heart, we characterized the electrophysiology of single cardiomyocytes isolated from adult transgenic (Tr) mice with cardiac-specific overexpression of CYP2J2. CYP2J2 Tr cardiomyocytes had a shortened action potential. At 90% repolarization, the action potential duration (APD) was 30.6 +/- 3.0 ms (n = 22) in wild-type (Wt) cells and 20.2 +/- 2.3 ms (n = 19) in CYP2J2 Tr cells (p < 0.005). This shortening was probably due to enhanced maximal peak transient outward K(+) currents (I(to,peak)), which were 38.6 +/- 2.8 and 54.4 +/- 4.9 pA/pF in Wt and CYP2J2 Tr cells, respectively (p < 0.05). In contrast, the late portion of the transient outward K(+) current (I(to,280ms)), the slowly inactivating outward K(+) current (I(K,slow)), and the voltage-gated Na(+) current (I(Na)) were not significantly altered in CYP2J2 Tr cells. N-Methylsulphonyl-6-(2-proparglyloxy-phenyl)hexanamide (MS-PPOH), a specific inhibitor of EET biosynthesis, significantly reduced I(to,peak) and increased APD in CYP2J2 Tr cardiomyocytes but not in Wt cells. Intracellular dialysis with a monoclonal antibody against CYP2J2 also significantly reduced I(to,peak) and increased APD in CYP2J2 Tr cardiomyocytes. Addition of 11,12-EET or 8-bromo-cAMP significantly reversed the MS-PPOH- or monoclonal antibody-induced changes in I(to,peak) and APD in CYP2J2 Tr cells. Together, our data demonstrate that shortening of the action potential in CYP2J2 Tr cardiomyocytes is associated with enhanced I(to,peak) via an EET-dependent, cAMP-mediated mechanism.
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Affiliation(s)
- Qingen Ke
- National Institutes of Health/NIEHS, 111 T. W. Alexander Drive, Building 101, Room D236, Research Triangle Park, NC 27709, USA.
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Okamura M, Kakei M, Ichinari K, Miyamura A, Oketani N, Koriyama N, Tei C. State-dependent modification of ATP-sensitive K+ channels by phosphatidylinositol 4,5-bisphosphate. Am J Physiol Cell Physiol 2001; 280:C303-8. [PMID: 11208525 DOI: 10.1152/ajpcell.2001.280.2.c303] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
With inside-out patch recordings in ventricular myocytes from the hearts of guinea pigs, we studied ATP-sensitive K+ (K(ATP)) channels activated by phosphatidylinositol 4,5-bisphosphate (PIP2) with respect to sensitivity to ATP when in either a rundown state (RS) or a non-rundown state (NRS). Rundown of K(ATP) channels was induced by exposure either to ATP-free solution or to ATP-free solution containing 19 microM Ca2+. Exposure of membrane patches to 10 microM PIP2 reactivated channels with both types of rundown. The reactivation by PIP2 did not require ATP in the bath. The IC50 of channels recovered from RS and before the rundown was 37.1 and 31.1 microM, respectively. PIP2 irreversibly increased the mean current when the channel was in the NRS. This was associated with a shift of IC50 to 250.6 microM after PIP2 exposure. PIP2 activates NRS K(ATP) channels by decreasing their sensitivity to ATP, whereas PIP2 reactivates RS-K(ATP) channels independently of ATP without changing ATP sensitivity.
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Affiliation(s)
- M Okamura
- First Department of Internal Medicine, Faculty of Medicine, Kagoshima University, Kagoshima 890-8520, Japan
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Picard S, Rouet R, Ducouret P, Puddu PE, Flais F, Criniti A, Monti F, Gérard JL. KATP channels and 'border zone' arrhythmias: role of the repolarization dispersion between normal and ischaemic ventricular regions. Br J Pharmacol 1999; 127:1687-95. [PMID: 10455327 PMCID: PMC1566150 DOI: 10.1038/sj.bjp.0702704] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. In order to investigate the role of KATP channel activation and repolarization dispersion on the 'border zone' arrhythmias induced by ischaemia-reperfusion, the effects of glibenclamide and bimakalim, agents modifying action potential (AP) duration, were studied in an in vitro model of myocardial 'border zone'. 2. The electrophysiological effects of 10 microM glibenclamide and 1 microM bimakalim (n=8 each), respectively KATP channel blocker and activator, were investigated on guinea-pig ventricular strips submitted partly to normal conditions (normal zone, NZ) and partly to simulated ischaemic then reperfused conditions (altered zone, AZ). 3. By preventing the ischaemia-induced AP shortening (P<0.0001), glibenclamide reduced the dispersion of AP duration 90% (APD90) between NZ and AZ (P<0.0001), and concomitantly inhibited the 'border zone' arrhythmias induced by an extrastimulus (ES), their absence being significantly related to the lessened APD90 dispersion (chi2=8.28, P<0.01). 4. Bimakalim, which also reduced the APD90 dispersion (P<0.005) due to differential AP shortening in normal and ischaemic tissues, decreased the incidence of myocardial conduction blocks (25% of preparations versus 83% in control, n=12, P<0.05) and favoured 'border zone' spontaneous arrhythmias (75% of preparations versus 25% in control, P<0.05). 5. During reperfusion, unlike bimakalim, glibenclamide inhibited the ES-induced arrhythmias and reduced the incidence of the spontaneous ones (12% of preparations versus 92% in control, P<0.05), this latter effect being significantly related (chi2=6.13, P<0.02) to the lessened ischaemia-induced AP shortening in the presence of glibenclamide (P<0.0001). 6. These results suggest that KATP blockade may protect the ischaemic-reperfused myocardium from 'border zone' arrhythmias concomitantly with a reduction of APD90 dispersion between normal and ischaemic regions. Conversely, KATP channel activation may modify the incidence of conduction blocks and exacerbate the ischaemia-induced 'border zone' arrhythmias.
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Affiliation(s)
- S Picard
- Laboratory of Experimental Anaesthesiology and Cellular Physiology, University of Caen, Caen, France
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Bogaty P, Kingma JG, Robitaille NM, Plante S, Simard S, Charbonneau L, Dumesnil JG. Attenuation of myocardial ischemia with repeated exercise in subjects with chronic stable angina: relation to myocardial contractility, intensity of exercise and the adenosine triphosphate-sensitive potassium channel. J Am Coll Cardiol 1998; 32:1665-71. [PMID: 9822094 DOI: 10.1016/s0735-1097(98)00431-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVES This study characterized the attenuation of myocardial ischemia observed with re-exercise to determine whether: 1) a differing exercise intensity modifies this attenuation; 2) it could be explained by contractile down-regulation or stunning; 3) it is mediated by activation of ATP-sensitive potassium channels (K+-ATP). BACKGROUND Subjects with ischemic heart disease (IHD) frequently note less angina with re-exercise after a brief rest. Potential mechanisms of this 'warm-up' phenomenon have been little explored. METHODS IHD subjects with a positive exercise test were studied. Groups I and II (12 subjects each) underwent 2 successive Naughton protocol exercise echocardiography tests (with 1 min instead of 2 min stages for Group II). Group D (10 subjects) had type II diabetes, were on > or =10 mg daily of the K+-ATP blocker, glibenclamide, and underwent the group I exercise protocol. The ischemic threshold or rate-pressure product at 1 mm ST segment depression, ST depression corresponding to the peak rate-pressure product of the first exercise (maximum ST depression equivalent), and left ventricular wall motion indexes before and immediately after each exercise were analyzed. RESULTS Exercise-induced myocardial ischemia with re-exercise was similarly attenuated in groups I, II, and D. The ischemic threshold was raised by nearly 20% with re-exercise (p=0.001, p=0.02, and p=0.02, respectively) and the maximum ST depression equivalent was nearly halved on re-exercise (p=0.005, p=0.006, and p=0.001, respectively). Exercise-induced wall motion dysfunction was attenuated with re-exercise. In group I, wall motion returned to the initial baseline score prior to exercise 2, whereas in the more intense protocol of group II, wall motion dysfunction persisted prior to exercise 2. CONCLUSIONS Thus, the attenuation of myocardial ischemia observed with re-exercise appears to be independent of the intensity of the exercise protocol and is not explained by down-regulation of myocardial contractility induced by the initial ischemic stimulus. Since results were similar in diabetic subjects on robust doses of glibenclamide, this phenomenon does not appear to be mediated by K+-ATP activation.
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Affiliation(s)
- P Bogaty
- Quebec Heart Institute/Laval Hospital, Laval University, Ste-Foy, Canada.
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Baczkó I, Leprán I, Papp JG. KATP channel modulators increase survival rate during coronary occlusion-reperfusion in anaesthetized rats. Eur J Pharmacol 1997; 324:77-83. [PMID: 9137916 DOI: 10.1016/s0014-2999(97)00064-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We investigated the effect of ATP-sensitive K+ channel (KATP) openers (pinacidil and cromakalim), and a KATP blocker (glibenclamide) on reperfusion-induced arrhythmias in pentobarbitone-anaesthetized rats. Arrhythmias were induced by reperfusion following a 6 min ligation of the left main coronary artery. Rats were pretreated with pinacidil (0.1 or 0.3 mg/kg), or cromakalim (28 or 56 micrograms/kg), or glibenclamide (5 mg/kg), or vehicle. Pinacidil and cromakalim produced dose-related reductions in blood pressure. Pinacidil (0.1 mg/kg) and cromakalim (56 micrograms/kg) significantly decreased the incidence of reperfusion-induced ventricular fibrillation and increased survival. Glibenclamide did not decrease ventricular fibrillation incidence, yet improved survival by increasing the possibility of recovery from ventricular fibrillation. The present study suggests that both opening and blocking KATP channels may increase survival during coronary occlusion and reperfusion in anaesthetized rats.
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Affiliation(s)
- I Baczkó
- Department of Pharmacology, Albert Szent-Györgyi Medical University, Szeged, Hungary
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West PD, Bursill JA, Wyse KR, Martin DK, Campbell TJ. Effect of Dofetilide and d-Sotalol on the ATP-Sensitive Potassium Channel of Rabbit Ventricular Myocytes. J Cardiovasc Pharmacol Ther 1996; 1:307-312. [PMID: 10684431 DOI: 10.1177/107424849600100406] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND: The ability of dofetilide and d-sotalol to maintain their class III action during ischemia is uncertain. We investigated the effect of these two drugs on the ATP-sensitive potassium channel (I(KATP)), which plays a major role in ischemia-induced action potential duration shortening. METHODS AND RESULTS: The activity of I(KATP) channels was studied in excised membrane patches of single ventricular myocytes, obtained by standard enzymatic dissociation techniques from New Zealand white rabbits. Dofetilide demonstrated a dose-dependent block of I(KATP) with an EC(50) of 51 +/- 1 µM in inside-out patches, Its ability to block the channel was substantially less when applied to the external membrane surface. d-Sotalol significantly blocked I(KATP) (42% reduction) at a concentration of 10 µM but not at 1 µM. As with dofetilide, its ability to block I(KATP) was reduced when applied externally. CONCLUSIONS: We conclude that dofetilide and d-sotalol block the ATP-sensitive potassium channel, but dofetilide does so only at concentrations much greater than those required for block of the delayed rectifier potassium channel. d-Sotalol in contrast shows modest blockade of I(KATP) at concentrations in the upper range of those seen during its clinical use.
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Affiliation(s)
- PD West
- Departments of Cardiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia
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Rohmann S, Weygandt H, Schelling P, Kie Soei L, Verdouw PD, Lues I. Involvement of ATP-sensitive potassium channels in preconditioning protection. Basic Res Cardiol 1994; 89:563-76. [PMID: 7702545 DOI: 10.1007/bf00794956] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Single or multiple brief periods of ischemia (preconditioning, PC) have been shown to protect the myocardium from infarction during a subsequent more prolonged ischemic insult. To test the hypothesis that opening of ATP-sensitive potassium channels (KATP) is involved in this mechanism, either bimakalim, a KATP channel opener, or glibenclamide, a KATP channel blocker, were administered to mimic or to block preconditioning protection in barbital-anesthetized pigs. PC was elicited by a single period of 10 min left anterior descending coronary artery (LADCA) occlusion followed by 15 min of reperfusion before the LADCA was reoccluded for 60 min. Instead of PC, bimakalim infusion was started 15 min before the 60 min LADCA occlusion (TCO) and stopped with the onset of ischemia. Glibenclamide was administered either for 10 min prior to the PC protocol, before bimakalim infusion, or before TCO. Regional wall function was quantified with ultrasonic crystals aligned to measure wall thickening (% delta WT). At the end of the protocol, infarct size was determined by incubating myocardium with p-nitrobluetetrazolium. In seven preconditioned pigs, infarct size was 9.9 +/- 5.1% of the risk region compared with 65.9 +/- 6.0% in the seven control pigs subjected to 60 min of ischemia only (p < 0.001). In seven pigs treated with bimakalim, infarct size was reduced to 35.3 +/- 6.6 (p < 0.05 vs. controls). Blocking ATP-sensitive potassium channels with glibenclamide prior to PC abolished its protective effect (infarct size, 62.2 +/- 4.5%; p < 0.001 vs. PC alone). Glibenclamide also antagonized the protective effect of bimakalim (infarct size, 55.2 +/- 4.0%), but did not affect infarct size, when solely administered prior to the prolonged ischemic period (62.2 +/- 4.3%). We conclude that in swine myocardium KATP channels are involved in the protective effect of ischemic preconditioning, since glibenclamide completely abolished the protective effect of preconditioning, while bimakalim could--at least in part--mimic it.
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Affiliation(s)
- S Rohmann
- E. Merck, Department of Preclinical Cardiovascular Research, Darmstadt, Germany
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