Cardioprotective mechanism of diazoxide involves the inhibition of succinate dehydrogenase

Connexin 43 modulates reverse electron transfer in cardiac mitochondria from inducible knock-out Cx43Cre-ER(T)/fl mice by altering the coenzyme Q pool

Succinate accumulates during myocardial ischemia and is rapidly oxidized during reperfusion, leading to reactive oxygen species (ROS) production through reverse electron transfer (RET) from mitochondrial complex II to complex I, and favoring cell death. Given that connexin 43 (Cx43) modulates mitochondrial ROS production, we investigated whether Cx43 influences RET using inducible knock-out Cx43Cre-ER(T)/fl mice. Oxygen consumption, ROS production, membrane potential and coenzyme Q (CoQ) pool were analyzed in subsarcolemmal (SSM, expressing Cx43) and interfibrillar (IFM) cardiac mitochondria isolated from wild-type Cx43fl/fl mice and Cx43Cre-ER(T)/fl knock-out animals treated with 4-hydroxytamoxifen (4OHT). In addition, infarct size was assessed in isolated hearts from these animals submitted to ischemia-reperfusion (IR), and treated or not with malonate, a complex II inhibitor attenuating RET. Succinate-dependent ROS production and RET were significantly lower in SSM, but not IFM, from Cx43-deficient animals. Mitochondrial membrane potential, a RET driver, was similar between groups, whereas CoQ pool (2.165 ± 0.338 vs. 4.18 ± 0.55 nmol/mg protein, p < 0.05) and its reduction state were significantly lower in Cx43-deficient animals. Isolated hearts from Cx43Cre-ER(T)/fl mice treated with 4OHT had a smaller infarct size after IR compared to Cx43fl/fl, despite similar concentration of succinate at the end of ischemia, and no additional protection by malonate. Cx43 deficiency attenuates ROS production by RET in SSM, but not IFM, and was associated with a decrease in CoQ levels and a change in its redox state. These results may partially explain the reduced infarct size observed in these animals and their lack of protection by malonate.

Kir1.1 and SUR1 are not implicated as subunits of an adenosine triphosphate-sensitive potassium channel involved in diazoxide cardioprotection

Objective

The adenosine triphosphate-sensitive potassium channel opener diazoxide mimics ischemic preconditioning and is cardioprotective. Clarification of diazoxide's site and mechanism of action could lead to targeted pharmacologic therapies for patients undergoing cardiac surgery. Several mitochondrial candidate proteins have been investigated as potential adenosine triphosphate-sensitive potassium channel components. Renal outer medullary potassium (Kir1.1) and sulfonylurea sensitive regulatory subunit 1 have been suggested as subunits of a mitochondrial adenosine triphosphate-sensitive potassium channel. We hypothesized that pharmacologic blockade or genetic deletion (knockout) of renal outer medullary potassium and sensitive regulatory subunit 1 would result in loss of diazoxide cardioprotection in models of global ischemia with cardioplegia.

Methods

Myocyte volume and contractility were compared after Tyrode's physiologic solution (20 minutes), stress (hyperkalemic cardioplegia ± diazoxide, ± VU591 (Kir1.1 inhibitor), N = 9 to 23 each, 20 min), and Tyrode's (20 minutes). Isolated mouse (wild-type, sensitive regulatory subunit 1 [-/-], and cardiac knockout renal outer medullary potassium) hearts were given cardioplegia ± diazoxide (N = 9-16 each) before global ischemia (90 minutes) and 30 minutes reperfusion. Left ventricular pressures were compared before and after ischemia.

Results

Stress (cardioplegia) was associated with reduced myocyte contractility that was prevented by diazoxide. Isolated myocytes were not responsive to diazoxide in the presence of VU591. In isolated hearts, diazoxide improved left ventricular function after prolonged ischemia compared with cardioplegia alone in wild-type and knockout (sensitive regulatory subunit 1 [-/-] and cardiac knockout renal outer medullary potassium) mice.

Conclusions

Isolated myocyte and heart models may measure independent and separate actions of diazoxide. By definitive genetic deletion, these data indicate that sensitive regulatory subunit 1 and renal outer medullary potassium are not implicated in cardioprotection by diazoxide.

Metabolomics analysis in rat hearts with ischemia/reperfusion injury after diazoxide postconditioning

Background: Diazoxide is a selective mitochondrial-sensitive potassium channel opening agent that has a definite effect on reducing myocardial ischemia/reperfusion injury (MIRI). However, the exact effects of diazoxide postconditioning on the myocardial metabolome remain unclear, which might contribute to the cardioprotective effects of diazoxide postconditioning. Methods: Rat hearts subjected to Langendorff perfusion were randomly assigned to the normal (Nor) group, ischemia/reperfusion (I/R) group, diazoxide (DZ) group and 5-hydroxydecanoic acid + diazoxide (5-HD + DZ) group. The heart rate (HR), left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), and maximum left ventricular pressure (+dp/dtmax) were recorded. The mitochondrial Flameng scores were analysed according to the ultrastructure of the ventricular myocardial tissue in the electron microscopy images. Rat hearts of each group were used to investigate the possible metabolic changes relevant to MIRI and diazoxide postconditioning. Results: The cardiac function indices in the Nor group were better than those in the other groups at the end point of reperfusion, and the HR, LVDP and +dp/dt_max of the Nor group at T2 were significantly higher than those of the other groups. Diazoxide postconditioning significantly improved cardiac function after ischaemic injury, and the HR, LVDP and +dp/dt_max of the DZ group at T2 were significantly higher than those of the I/R group, which could be abolished by 5-HD. The HR, LVDP and +dp/dt_max of the 5-HD + DZ group at T2 were significantly lower than those of the DZ group. The myocardial tissue in the Nor group was mostly intact, while it exhibited considerable damage in the I/R group. The ultrastructural integrity of the myocardium in the DZ group was higher than that in the I/R and 5-HD + DZ groups. The mitochondrial Flameng score in the Nor group was lower than that in the I/R, DZ and 5-HD + DZ groups. The mitochondrial Flameng score in the DZ group was lower than that in the I/R and 5-HD + DZ groups. Five metabolites, namely, L-glutamic acid, L-threonine, citric acid, succinate, and nicotinic acid, were suggested to be associated with the protective effects of diazoxide postconditioning on MIRI. Conclusion: Diazoxide postconditioning may improve MIRI via certain metabolic changes. This study provides resource data for future studies on metabolism relevant to diazoxide postconditioning and MIRI.

ATP-Sensitive Potassium Channel Opener Diazoxide Reduces Myocardial Stunning in a Porcine Regional With Subsequent Global Ischemia Model

Background ATP-sensitive potassium channels are inhibited by ATP and open during metabolic stress, providing endogenous myocardial protection. Pharmacologic opening of ATP potassium channels with diazoxide preserves myocardial function following prolonged global ischemia, making it an ideal candidate for use during cardiac surgery. We hypothesized that diazoxide would reduce myocardial stunning after regional ischemia with subsequent prolonged global ischemia, similar to the clinical situation of myocardial ischemia at the time of revascularization. Methods and Results Swine underwent left anterior descending occlusion (30 minutes), followed by 120 minutes global ischemia protected with hyperkalemic cardioplegia±diazoxide (N=6 each), every 20 minutes cardioplegia, then 60 minutes reperfusion. Cardiac output, time to wean from cardiopulmonary bypass, left ventricular (LV) function, caspase-3, and infarct size were compared. Six animals in the diazoxide group separated from bypass by 30 minutes, whereas only 4 animals in the cardioplegia group separated. Diazoxide was associated with shorter but not significant time to wean from bypass (17.5 versus 27.0 minutes; P=0.13), higher, but not significant, cardiac output during reperfusion (2.9 versus 1.5 L/min at 30 minutes; P=0.05), and significantly higher left ventricular ejection fraction at 30 minutes (42.5 versus 15.8%; P<0.01). Linear mixed regression modeling demonstrated greater left ventricular developed pressure (P<0.01) and maximum change in ventricular pressure during isovolumetric contraction (P<0.01) in the diazoxide group at 30 minutes of reperfusion. Conclusions Diazoxide reduces myocardial stunning and facilitates separation from cardiopulmonary bypass in a model that mimics the clinical setting of ongoing myocardial ischemia before revascularization. Diazoxide has the potential to reduce myocardial stunning in the clinical setting.

Peculiarities of Action of Catecholamines and their Metabolites in the Regulation of Cardiomyocyte Enzymes

Абстрактный Background: Myocardial ischemia is accompanied by a significant increase in adrenaline content in the heart. By its nature, sympathetic hyperactivation is accompanied by increased formation of products of enzymatic and non-enzymatic metabolism of adrenaline and its analogues, which can change the use of ATP by cells, change the activity of mitochondrial and cytosolic enzymes, contributing to disruption of bioenergetic adaptation, antioxidant defense system and levels of intercellular modulators such as AMP and adenosine. The study objective was to explore the features of adrenaline and its analogues in the regulation of the activity of mitochondrial and cytoplasmic enzymes of cardiomyocytes. Methods: The experiment was carried out on 65 three-month-old male Wistar rats weighing 60-190 g. To study the effects of catecholamines and their metabolites in the regulation of mitochondrial and cytoplasmic enzymes activity of cardiomyocytes, experimental rats were put to death by intraperitoneal injection of 10% ketamine in an amount of 0.25 mg per 100 g. Activity of mitochondrial succinate dehydrogenase, cytochrome c oxidase, mitochondrial DNP-activated ATPase, adenosine deaminase (AD), AMP deaminase (AMPD), glutathione reductase (GR) and glutathione peroxidase (GPO) were determined. Results: Dopamine has the greatest activating effect on cardiac mitochondrial ADH, adrenaline on CHO, and adrenochrome and adrenoxyl on ATPase. Isadrine and dopamine reduce cardiac AMPase activity. An activating effect on cardiac mitochondrial AMP deaminase was found only in norepinephrine.  Заключение. В кардиомиоцитах адреналин активирует цитозольные ферменты метаболизма пуриновых нуклеотидов AD и AMPD, а также повышает уровень перекисного окисления липидов (MDA и DC). Это доказывает, что адреналин, воздействуя на адренорецепторные механизмы, приводит организм в состояние окислительного стресса. Гормоны-медиаторы симпато-адреналовой системы адреналин, дофамин, норадреналин, изадрин и метаболиты катехоламинов (адренохром и адреноксил), изменяют активность ферментов митохондриальной дыхательной цепи кардиомиоцитов, а также регулируют процессы тканевого дыхания, переводя митохондрии в состояние «рыхлого» состояния. «сочетание дыхания и фосфорилирования.   

Cardioprotective mechanisms of mitochondria-targeted S-nitrosating agent and adenosine triphosphate-sensitive potassium channel opener are mutually exclusive

Background

Myocytes exposed to stress exhibit significant swelling and reduced contractility. These consequences are ameliorated by adenosine triphosphate-sensitive potassium (KATP) channel opener diazoxide (DZX) via an unknown mechanism. KATP channel openers also provide cardioprotection in multiple animal models. Nitric oxide donors are similarly cardioprotective, and their combination with KATP activation may provide synergistic benefit. We hypothesized that mitochondria-targeted S-nitrosating agent (MitoSNO) would provide synergistic cardioprotection with DZX.

Methods

Myocyte volume and contractility were compared following Tyrode's physiologic solution (20 minutes) and stress (hyperkalemic cardioplegia [CPG] ± DZX; n = 5-20 each; 20 minutes) with or without MitoSNO (n = 5-11 each) at the end of stress, followed by Tyrode's solution (20 minutes). Isolated mouse hearts received CPG ± DZX (n = 8-10 each) before global ischemia (90 minutes) with or without MitoSNO (n = 8 each) at the end of ischemia, followed by reperfusion (30 minutes). Left ventricular (LV) pressures were compared using a linear mixed model to assess the impact of treatment on the outcome, adjusting for baseline and balloon volume.

Results

Stress (CPG) was associated with reduced myocyte contractility that was prevented by DZX and MitoSNO individually; however, their combination was associated with loss of cardioprotection. Similarly, DZX and MitoSNO improved LV function after prolonged ischemia compared with CPG alone, and cardioprotection was lost with their combination.

Conclusions

MitoSNO and DZX provide cardioprotection that is lost with their combination, suggesting mutually exclusive mechanisms of action. The lack of a synergistic beneficial effect informs the current knowledge of the cardioprotective mechanisms of DZX and will aid planning of future clinical trials.

Mitochondrial complex II and reactive oxygen species in disease and therapy

Increasing evidence points to the respiratory Complex II (CII) as a source and modulator of reactive oxygen species (ROS). Both functional loss of CII as well as its pharmacological inhibition can lead to ROS generation in cells, with a relevant impact on the development of pathophysiological conditions, i.e. cancer and neurodegenerative diseases. While the basic framework of CII involvement in ROS production has been defined, the fine details still await clarification. It is important to resolve these aspects to fully understand the role of CII in pathology and to explore its therapeutic potential in cancer and other diseases.

Energy substrate metabolism and mitochondrial oxidative stress in cardiac ischemia/reperfusion injury

The heart is the most metabolically flexible organ with respect to the use of substrates available in different states of energy metabolism. Cardiac mitochondria sense substrate availability and ensure the efficiency of oxidative phosphorylation and heart function. Mitochondria also play a critical role in cardiac ischemia/reperfusion injury, during which they are directly involved in ROS-producing pathophysiological mechanisms. This review explores the mechanisms of ROS production within the energy metabolism pathways and focuses on the impact of different substrates. We describe the main metabolites accumulating during ischemia in the glucose, fatty acid, and Krebs cycle pathways. Hyperglycemia, often present in the acute stress condition of ischemia/reperfusion, increases cytosolic ROS concentrations through the activation of NADPH oxidase 2 and increases mitochondrial ROS through the metabolic overloading and decreased binding of hexokinase II to mitochondria. Fatty acid-linked ROS production is related to the increased fatty acid flux and corresponding accumulation of long-chain acylcarnitines. Succinate that accumulates during anoxia/ischemia is suggested to be the main source of ROS, and the role of itaconate as an inhibitor of succinate dehydrogenase is emerging. We discuss the strategies to modulate and counteract the accumulation of substrates that yield ROS and the therapeutic implications of this concept.

Diazoxide Preconditioning of Nonhuman Primate Pancreas Improves Islet Isolation Outcomes by Mitochondrial Protection

OBJECTIVES

Previously, we showed that diazoxide (DZ), an effective ischemic preconditioning agent, protected rodent pancreas against ischemia-reperfusion injury. Here, we further investigate whether DZ supplementation to University of Wisconsin (UW) solution during pancreas procurement and islet isolation has similar cytoprotection in a preclinical nonhuman primate model.

METHODS

Cynomolgus monkey pancreata were flushed with UW or UW + 150 μM DZ during procurement and preserved for 8 hours before islet isolation.

RESULTS

First, a significantly higher islet yield was observed in UW + DZ than in UW (57,887 vs 23,574 IEq/pancreas and 5396 vs 1646 IEq/g). Second, the DZ treated islets had significantly lower apoptotic cells per islet (1.64% vs 9.85%). Third, DZ significantly inhibited ROS surge during reperfusion with a dose-response manner. Fourth, DZ improved in vitro function of isolated islets determined by mitochondrial potentials and calcium influx in responses to glucose and KCI. Fifth, the DZ treated islets had much higher cure rate and better glycemia control in diabetic mice transplant model.

CONCLUSIONS

This study showed a strong mitochondrial protection of DZ on nonhuman primate islets against ischemia-reperfusion injury that provides strong evidence for its clinical application in islet and pancreas transplantation.

Ischemic postconditioning prevents surge of presynaptic glutamate release by activating mitochondrial ATP-dependent potassium channels in the mouse hippocampus

A mild ischemic load applied after a lethal ischemic insult reduces the subsequent ischemia–reperfusion injury, and is called ischemic postconditioning (PostC). We studied the effect of ischemic PostC on synaptic glutamate release using a whole-cell patch-clamp technique. We recorded spontaneous excitatory post-synaptic currents (sEPSCs) from CA1 pyramidal cells in mouse hippocampal slices. The ischemic load was perfusion of artificial cerebrospinal fluid (ACSF) equilibrated with mixed gas (95% N₂ and 5% CO₂). The ischemic load was applied for 7.5 min, followed by ischemic PostC 30 s later, consisting of three cycles of 15 s of reperfusion and 15 s of re-ischemia. We found that a surging increase in sEPSCs frequency occurred during the immediate-early reperfusion period after the ischemic insult. We found a significant positive correlation between cumulative sEPSCs and the number of dead CA1 neurons (r = 0.70; p = 0.02). Ischemic PostC significantly suppressed this surge of sEPSCs. The mitochondrial K_ATP (mito-K_ATP) channel opener, diazoxide, also suppressed the surge of sEPSCs when applied for 15 min immediately after the ischemic load. The mito-K_ATP channel blocker, 5-hydroxydecanoate (5-HD), significantly attenuated the suppressive effect of both ischemic PostC and diazoxide application on the surge of sEPSCs. These results suggest that the opening of mito-K_ATP channels is involved in the suppressive effect of ischemic PostC on synaptic glutamate release and protection against neuronal death. We hypothesize that activation of mito-K_ATP channels prevents mitochondrial malfunction and breaks mutual facilitatory coupling between glutamate release and Ca²⁺ entry at presynaptic sites.

Selective Inhibition of Succinate Dehydrogenase in Reperfused Myocardium with Intracoronary Malonate Reduces Infarct Size

Inhibition of succinate dehydrogenase (SDH) with malonate during reperfusion reduces infarct size in isolated mice hearts submitted to global ischemia. However, malonate has toxic effects that preclude its systemic administration in animals. Here we investigated the effect of intracoronary malonate on infarct size in pigs submitted to transient coronary occlusion. Under baseline conditions, 50 mmol/L of intracoronary disodium malonate, but not lower concentrations, transiently reduced systolic segment shortening in the region perfused by the left anterior descending coronary artery (LAD) in open-chest pigs. To assess the effects of SDH inhibition on reperfusion injury, saline or malonate 10 mmol/L were selectively infused into the area at risk in 38 animals submitted to ischemia-reperfusion. Malonate improved systolic shortening in the area at risk two hours after 15 min of ischemia (0.18 ± 0.07 vs 0.00 ± 0.01 a.u., p = 0.025, n = 3). In animals submitted to 40 min of ischemia, malonate reduced reactive oxygen species production (MitoSOX staining) during initial reperfusion and limited infarct size (36.46 ± 5.35 vs 59.62 ± 4.00%, p = 0.002, n = 11), without modifying reperfusion arrhythmias. In conclusion, inhibition of SDH with intracoronary malonate during early reperfusion limits reperfusion injury and infarct size in pigs submitted to transient coronary occlusion without modifying reperfusion arrhythmias or contractile function in distant myocardium.

Moving Forwards by Blocking Back-Flow: The Yin and Yang of MI Therapy

Mitochondrial reactive oxygen species production has emerged as an important pathological mechanism in myocardial ischemia/reperfusion injury. Attempts at targeting reactive oxygen species by scavenging using antioxidants have, however, been clinically disappointing. This review will provide an overview of the current understanding of mitochondrial reactive oxygen species in ischemia/reperfusion injury. We will outline novel therapeutic approaches designed to directly target the mitochondrial respiratory chain and prevent excessive reactive oxygen species production and its associated pathology. This approach could lead to more effective interventions in an area where there is an urgent need for new treatments.

Adenosine Triphosphate-Sensitive Potassium Channel Kir Subunits Implicated in Cardioprotection by Diazoxide

Background

ATP-sensitive potassium (K_ATP) channel openers provide cardioprotection in multiple models. Ion flux at an unidentified mitochondrial K_ATP channel has been proposed as the mechanism. The renal outer medullary kidney potassium channel subunit, potassium inward rectifying (Kir)1.1, has been implicated as a mitochondrial channel pore-forming subunit. We hypothesized that subunit Kir1.1 is involved in cardioprotection (maintenance of volume homeostasis and contractility) of the K_ATP channel opener diazoxide (DZX) during stress (exposure to hyperkalemic cardioplegia [CPG]) at the myocyte and mitochondrial levels.

Methods and Results

Kir subunit inhibitor Tertiapin Q (TPN-Q) was utilized to evaluate response to stress. Mouse ventricular mitochondrial volume was measured in the following groups: isolation buffer; 200 μmol/L of ATP; 100 μmol/L of DZX+200 μmol/L of ATP; or 100 μmol/L of DZX+200 μmol/L of ATP+TPN-Q (500 or 100 nmol/L). Myocytes were exposed to Tyrode’s solution (5 minutes), test solution (Tyrode’s, cardioplegia [CPG], CPG+DZX, CPG+DZX+TPN-Q, Tyrode’s+TPN-Q, or CPG+TPN-Q), N=12 for all (10 minutes); followed by Tyrode’s (5 minutes). Volumes were compared. TPN-Q, with or without DZX, did not alter mitochondrial or myocyte volume. Stress (CPG) resulted in myocyte swelling and reduced contractility that was prevented by DZX. TPN-Q prevented the cardioprotection afforded by DZX (volume homeostasis and maintenance of contractility).

Conclusions

TPN-Q inhibited myocyte cardioprotection provided by DZX during stress; however, it did not alter mitochondrial volume. Because TPN-Q inhibits Kir1.1, Kir3.1, and Kir3.4, these data support that any of these Kir subunits could be involved in the cardioprotection afforded by diazoxide. However, these data suggest that mitochondrial swelling by diazoxide does not involve Kir1.1, 3.1, or 3.4.

Diazoxide Cardioprotection Is Independent of Adenosine Triphosphate-Sensitive Potassium Channel Kir6.1 Subunit in Response to Stress

BACKGROUND

The sarcolemmal adenosine triphosphate-sensitive potassium channel (sK(ATP)), composed primarily of potassium inward rectifier (Kir) 6.2 and sulfonylurea receptor 2A subunits, has been implicated in cardiac myocyte volume regulation during stress; however, it is not involved in cardioprotection by the adenosine triphosphate-sensitive potassium channel (K(ATP)) channel opener diazoxide (7-chloro-3-methyl-1,2,4-benzothiadiazine-1,1-dioxide [DZX]). Paradoxically, the sK(ATP) channel subunit Kir6.2 is necessary for detrimental myocyte swelling secondary to stress. The Kir6.1 subunit can also contribute to K(ATP) channels in the heart, and we hypothesized that this subunit might play a role in myocyte volume regulation in response to stress.

STUDY DESIGN

Isolated cardiac myocytes from either wild-type mice or mice lacking the Kir6.1 subunit (Kir6.1[-/-]) were exposed to control Tyrode's solution (TYR) for 20 minutes, test solution (TYR, hypothermic hyperkalemic cardioplegia [CPG], or CPG + K(ATP) channel opener DZX [CPG + DZX]) for 20 minutes, followed by TYR for 20 minutes. Myocyte volume and contractility were measured and analyzed.

RESULTS

Both wild-type and Kir6.1(-/-) myocytes demonstrated substantial swelling during exposure to stress (CPG), which was prevented by DZX. Wild-type myocytes also demonstrated reduced contractility during stress of CPG that was prevented by DZX. However, Kir6.1(-/-) myocytes did not show reduced contractility during stress.

CONCLUSIONS

These data indicate that K(ATP) channel subunit Kir6.1 is not necessary for DZX's maintenance of cell volume during the stress of CPG. The absence of Kir6.1 does not affect the contractile properties of myocytes during stress, suggesting the absence of Kir6.1 improves myocyte tolerance to stress via an unknown mechanism.

Cardioprotective benefits of adenosine triphosphate-sensitive potassium channel opener diazoxide are lost with administration after the onset of stress in mouse and human myocytes

BACKGROUND

Adenosine triphosphate-sensitive (KATP) potassium channel opener diazoxide (DZX) maintains myocyte volume and contractility during stress via an unknown mechanism when administered at the onset of stress. This study was performed to investigate the cardioprotective potential of DZX when added after the onset of the stresses of hyperkalemic cardioplegia, metabolic inhibition, and hypo-osmotic stress.

STUDY DESIGN

Isolated mouse ventricular and human atrial myocytes were exposed to control Tyrode's solution (TYR) for 10 to 20 minutes, test solution for 30 minutes (hypothermic hyperkalemic cardioplegia [CPG], CPG + 100uM diazoxide [CPG+DZX], metabolic inhibition [MI], MI+DZX, mild hypo-osmotic stress [0.9T], or 0.9T + DZX), with DZX added after 10 or 20 minutes of stress, followed by 20 minutes of re-exposure to TYR (±DZX). Myocyte volume (human + mouse) and contractility (mouse) were compared.

RESULTS

Mouse and human myocytes demonstrated significant swelling during exposure to CPG, MI, and hypo-osmotic stress that was not prevented by DZX when administered either at 10 or 20 minutes after the onset of stress. Contractility after the stress of CPG in mouse myocytes significantly declined when DZX was administered 20 minutes after the onset of stress (p < 0.05 vs TYR). Contractility after hypo-osmotic stress in mouse myocytes was not altered by the addition of DZX.

CONCLUSIONS

To maintain myocyte volume homeostasis and contractility during stress (hyperkalemic cardioplegia, metabolic inhibition, and hypo-osmotic stress), KATP channel opener diazoxide requires administration at the onset of stress in this isolated myocyte model. These data have potential implications for any future clinical application of diazoxide.