scholarly journals Effects of ischemia and reperfusion on isolated ventricular myocytes from young adult and aged Fischer 344 rat hearts

2008 ◽  
Vol 294 (5) ◽  
pp. H2174-H2183 ◽  
Author(s):  
J. Darcy O'Brien ◽  
Jessica H. Ferguson ◽  
Susan E. Howlett
Keyword(s):  
Young Adult ◽  
Cell Viability ◽  
Ventricular Myocytes ◽  
Contractile Function ◽  
Ischemia And Reperfusion ◽  
Early Reperfusion ◽  
Aging Heart ◽  
Fischer 344 ◽  
Simulated Ischemia ◽  
The Impact

This study examined the impact of age on contractile function, Ca2+ homeostasis, and cell viability in isolated myocytes exposed to simulated ischemia and reperfusion. Ventricular myocytes were isolated from anesthetized young adult (3 mo) and aged (24 mo) male Fischer 344 rats. Cells were field-stimulated at 4 Hz (37°C), exposed to simulated ischemia, and reperfused with Tyrode solution. Cell shortening and intracellular Ca2+ were measured simultaneously with an edge detector and fura-2. Cell viability was assessed by Trypan blue exclusion. Ischemia (20–45 min) depressed amplitudes of contraction equally in isolated myocytes from young adult and aged animals. The degree of postischemic contractile depression (stunning) was comparable in both groups. Ca2+ transient amplitudes were depressed in early reperfusion in young adult and aged cells and then recovered to preischemic levels in both groups. Cell viability also declined equally in reperfusion in both groups. In short, some cellular responses to simulated ischemia and reperfusion were similar in both groups. Even so, aged myocytes exhibited a much greater and more prolonged accumulation of diastolic Ca2+ in ischemia and in early reperfusion compared with myocytes from younger animals. In addition, the degree of mechanical alternans in ischemia increased significantly with age. The observation that there is an age-related increase in accumulation of diastolic Ca2+ in ischemia and early reperfusion may account for the increased sensitivity to ischemia and reperfusion injury in the aging heart. The occurrence of mechanical alternans in ischemia may contribute to contractile dysfunction in ischemia in the aging heart.

Simulated ischemia-induced preconditioning of isolated ventricular myocytes from young adult and aged Fischer-344 rat hearts

2008 ◽  
Vol 295 (2) ◽  
pp. H768-H777 ◽  
Author(s):  
J. Darcy O'Brien ◽  
Susan E. Howlett
Keyword(s):  
Young Adult ◽  
Ventricular Myocytes ◽  
Contractile Function ◽  
Marked Rise ◽  
Early Reperfusion ◽  
Fischer 344 ◽  
Simulated Ischemia ◽  
Intracellular Ca ◽  
The Impact ◽  
Isolated Ventricular Myocytes

The impact of ischemic preconditioning (IPC) on contraction, Ca2+ homeostasis, and cell survival was compared in isolated ventricular myocytes from young adult (∼3 mo) and aged (∼24 mo) male Fischer-344 rats. Myocytes were field stimulated at 4 Hz (37°C). Contraction (edge detector) and intracellular Ca2+ (fura-2) were measured simultaneously. Viability was assessed with trypan blue. All cells were exposed to 30 min of simulated ischemia followed by reperfusion. Some cells were preconditioned by exposure to 5 min of simulated ischemia before prolonged ischemia. Pretreatment with IPC abolished postischemic contractile depression, inhibited diastolic contracture, and increased Ca2+ transient amplitudes in reperfusion in young adult and aged cells. IPC did not affect the modest rise in diastolic Ca2+ in ischemia in young adult myocytes. However, IPC abolished the marked rise in diastolic Ca2+ observed in ischemia and early reperfusion in aged myocytes. IPC also suppressed mechanical alternans in ischemia in aged cells, but younger myocytes showed little evidence of mechanical alternans whether or not cells were preconditioned. IPC markedly improved cell viability in reperfusion in young adult but not aged cells. These results suggest that IPC augments the recovery of contractile function in reperfusion by increasing Ca2+ transient amplitudes in ventricular myocytes from young adult and aged rats. IPC reduced diastolic Ca2+ accumulation in ischemia in aged myocytes, which may diminish the severity of mechanical alternans in aged cells. Nonetheless, the efficacy of IPC is compromised in aging, as IPC did not improve survival of aged myocytes exposed to ischemia and reperfusion.

Effects of adenosine in simulated ischemia and reperfusion in guinea pig ventricular myocytes

1995 ◽  
Vol 269 (1) ◽  
pp. H121-H129 ◽  
Author(s):  
J. M. Cordeiro ◽  
G. R. Ferrier ◽  
S. E. Howlett
Keyword(s):  
Ventricular Myocytes ◽  
Contractile Activity ◽  
Receptor Blockade ◽  
Ischemia And Reperfusion ◽  
Tyrode Solution ◽  
Edge Detector ◽  
Early Reperfusion ◽  
Inward Current ◽  
Simulated Ischemia ◽  
A1 Receptor

Effects of adenosine (ADN) on cardiac cellular electrical and contractile activity were determined during ischemia and reperfusion. Electrical activity was recorded with conventional and voltage-clamp techniques. Contractions were monitored with a video edge detector. Myocytes were exposed to simulated ischemia (20 min), in the presence or absence of ADN (1-50 microM), and reperfused with Tyrode solution. ADN had no effects under control conditions. However, action potential abbreviation during ischemia was greater in the presence of ADN than for control, and recovery was delayed. In ischemia, Ca2+ current declined equally, and contractions were abolished in control and ADN-treated myocytes. In early reperfusion, oscillatory afterpotentials (OAP), transient inward current (ITI) and aftercontractions appeared, and contractions increased above preischemic levels. ADN abolished contractile overshoot and reduced incidence of OAP, ITI, and aftercontractions from 78 to 37.5%. The effects of exogenous ADN were inhibited by ADN A1-receptor blockade. Inhibition of endogenous ADN by 8-phenyltheophylline only increased incidence of ITI. Thus exogenous ADN in ischemia may protect the myocardium in reperfusion via A1 receptors.

scholarly journals Nonanticoagulant heparin reduces myocyte Na+ and Ca2+ loading during simulated ischemia and decreases reperfusion injury

2010 ◽  
Vol 298 (1) ◽  
pp. H102-H111 ◽  
Author(s):  
William H. Barry ◽  
Xiu Q. Zhang ◽  
Michael E. Halkos ◽  
Jakob Vinten-Johansen ◽  
Noriko Saegusa ◽  
...  
Keyword(s):  
Reperfusion Injury ◽  
Ventricular Myocytes ◽  
Myocardial Necrosis ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Metabolic Inhibition ◽  
Early Reperfusion ◽  
Simulated Ischemia ◽  
Sea Anemone Toxin ◽  
Voltage Clamping

Heparin desulfated at the 2- O and 3- O positions (ODSH) decreases canine myocardial reperfusion injury. We hypothesized that this occurs from effects on ion channels rather than solely from anti-inflammatory activities, as previously proposed. We studied closed-chest pigs with balloon left anterior descending coronary artery occlusion (75-min) and reperfusion (3-h). ODSH effects on [Na+]i (Na Green) and [Ca2+]i (Fluo-3) were measured by flow cytometry in rabbit ventricular myocytes after 45-min of simulated ischemia [metabolic inhibition with 2 mM cyanide, 0 glucose, 37°C, pacing at 0.5 Hz; i.e., pacing-metabolic inhibition (PMI)]. Na+/Ca2+ exchange (NCX) activity and Na+ channel function were assessed by voltage clamping. ODSH (15 mg/kg) 5 min before reperfusion significantly decreased myocardial necrosis, but neutrophil influx into reperfused myocardium was not consistently reduced. ODSH (100 μg/ml) reduced [Na+]i and [Ca2+]i during PMI. The NCX inhibitor KB-R7943 (10 μM) or the late Na+ current ( INa-L) inhibitor ranolazine (10 μM) reduced [Ca2+]i during PMI and prevented effects of ODSH on Ca2+ loading. ODSH also reduced the increase in Na+ loading in paced myocytes caused by 10 nM sea anemone toxin II, a selective activator of INa-L. ODSH directly stimulated NCX and reduced INa-L. These results suggest that in the intact heart ODSH reduces Na+ influx during early reperfusion, when INa-L is activated by a burst of reactive oxygen production. This reduces Na+ overload and thus Ca2+ influx via NCX. Stimulation of Ca2+ extrusion via NCX later after reperfusion may also reduce myocyte Ca2+ loading and decrease infarct size.

Annexin V staining during reperfusion detects cardiomyocytes with unique properties

2001 ◽  
Vol 281 (5) ◽  
pp. H1931-H1937 ◽  
Author(s):  
Prakash Narayan ◽  
Robert M. Mentzer ◽  
Robert D. Lasley
Keyword(s):  
Propidium Iodide ◽  
Ventricular Myocytes ◽  
Contractile Function ◽  
Ischemia Reperfusion ◽  
Annexin V ◽  
Cell Width ◽  
Simulated Ischemia ◽  
Propidium Iodide Staining ◽  
Membrane Blebs ◽  
Apoptosis And Necrosis

With the use of markers of sarcolemmal membrane permeability, cardiomyocyte models of ischemic injury have primarily addressed necrotic death during ischemia. In the present study, we used annexin V-propidium iodide staining to examine apoptosis and necrosis after simulated ischemia and simulated reperfusion in rat ventricular myocytes. Annexin V binds phosphatidylserine, a phosphoaminolipid thought to be externalized during apoptosis or programmed cell death. Propidium iodide is a marker of cell necrosis. Under baseline conditions, <1% of cardiomyocytes stained positive for annexin V. After 20 or 60 min of simulated ischemia, there was no increase in annexin V staining, although 60-min simulated ischemia resulted in significant propidium iodide staining. Twenty minutes of simulated ischemia, followed by 20 or 60 min of simulated reperfusion, resulted in 8–10% of myocytes staining positive for annexin V. Annexin V-positive cells retained both rod-shaped morphology and contractile function but exhibited the decreased cell width indicative of cell shrinkage. Baseline mitochondrial free Ca2+(111 ± 14 nM) was elevated in reperfused annexin V-negative cells (214 ± 22 nM), and further elevated in annexin V-positive myocytes (382 ± 9 nM). After 60 min of simulated reperfusion, caspase-3-like activity was observed in ∼3% of myocytes, which had a rounded appearance and membrane blebs. These results suggest that the use of annexin V after simulated ischemia-reperfusion uncovers a population of cardiomyocytes whose characteristics appear to be consistent with cells undergoing apoptosis.

scholarly journals Role of cation gradients in hypercontracture of myocytes during simulated ischemia and reperfusion

1993 ◽  
Vol 264 (6) ◽  
pp. H1896-H1906 ◽  
Author(s):  
M. Nishida ◽  
S. Borzak ◽  
B. Kraemer ◽  
J. P. Navas ◽  
R. A. Kelly ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Extracellular Fluid ◽  
High Energy ◽  
Ischemia And Reperfusion ◽  
High Energy Phosphates ◽  
Twitch Contraction ◽  
Adult Rat ◽  
Simulated Ischemia ◽  
The Relationship

We examined the relationship between transsarcolemmal cation gradients and hypercontracture of cardiac myocytes in ischemia and reperfusion using adult rat ventricular myocytes superfused with buffer mimicking normal or ischemic extracellular fluid. Contractile performance of electrically stimulated cells was recorded by an optical video system simultaneously with measurements of intracellular Ca2+ concentration ([Ca2+]i) using fura-2 or intracellular pH (pHi) using 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. While cells were exposed to simulated ischemia buffer, the transsarcolemmal H+ gradient was abolished, [Ca2+]i transient stopped, and twitch contraction of myocytes ceased. Upon reperfusion with normal buffer, H+ gradient was quickly restored, Ca2+ transients restarted with transient increase in systolic Ca2+, and twitch contraction restarted with development of hypercontracture, which continued after [Ca2+]i returned to preischemic level even in the presence of near-normal concentrations of high-energy phosphates. When the transsarcolemmal proton, Na+, and Ca2+ gradients were altered so that Na+ entry via Na(+)-H+ exchange and Ca2+ entry via Ca(2+)-Na+ exchange were made less favorable, the transient systolic overshoot of Ca2+ at reperfusion and development of hypercontracture was largely avoided. These results suggest that Na+ and then Ca2+ entry via the Na(+)-H+ and Na(+)-Ca2+ exchangers, respectively, probably contribute to the increase in [Ca2+]i and hypercontracture of myocytes at time of reperfusion in this model.

Further study on the role of HSP70 on Ca2+ homeostasis in rat ventricular myocytes subjected to simulated ischemia

2006 ◽  
Vol 290 (2) ◽  
pp. C583-C591 ◽  
Author(s):  
Jing Liu ◽  
Kenneth W. L. Kam ◽  
Gudrun H. Borchert ◽  
Gennadi M. Kravtsov ◽  
Heather J. Ballard ◽  
...  
Keyword(s):  
Antisense Oligonucleotide ◽  
Ventricular Myocytes ◽  
Contractile Function ◽  
Rat Ventricular Myocytes ◽  
Simulated Ischemia ◽  
Opioid Receptor Agonist ◽  
Plasmic Reticulum ◽  
Rat Ventricular Myocyte ◽  
Hsp70 Synthesis

We hypothesized that activation of heat shock protein 70 (HSP70) by preconditioning, which is known to confer delayed cardioprotection, attenuates the impaired handling of Ca2+ at multiple sites. To test the hypothesis, we determined how the ryanodine receptor (RyR), sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA), and Na+/Ca2+ exchanger (NCX) handled Ca2+ in rat ventricular myocytes preconditioned with a κ-opioid receptor agonist, U50488H (UP), followed by blockade of HSP70 with a selective antisense oligonucleotide and subsequently subjected to simulated ischemia. We determined the following: 1) the Ca2+ transients induced by electrical stimulation and caffeine, which provide the overall picture of Ca2+ homeostasis; 2) expression of RyR, SERCA, and NCX; and 3) Ca2+ fluxes via NCX by the use of 45Ca2+ in the rat ventricular myocyte. We found that UP increased the activity of RyR, SERCA, and NCX and the expression of RyR and SERCA. These effects led to increases in the release of Ca2+ from the sarcoplasmic reticulum via RyR and in the removal of Ca2+ from the cytoplasm by reuptake of Ca2+ to the SR via SERCA and by extrusion of Ca2+ out of the cell via NCX. UP also reduced mitochondrial Ca2+ accumulation. All of the effects of UP were either abolished or significantly attenuated by blockade of HSP70 synthesis with a selective antisense oligonucleotide. The results are evidence that activation of HSP70 by preconditioning improves the ischemia-impaired Ca2+ homeostasis at multiple sites in the heart, which may be responsible, at least partly, for attenuated Ca2+ overload, improved recovery in contractile function, and cardioprotection.

Effects of Atorvastatin on Transient Sodium Currents in Rat Normal, Simulated Ischemia, and Reperfusion Ventricular Myocytes

Pharmacology ◽  
2019 ◽  
Vol 105 (5-6) ◽  
pp. 320-328
Author(s):  
Jing Nie ◽  
Gang Wang ◽  
Guoyan Zhao ◽  
Xin Du ◽  
Liang Zhang ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Ischemia And Reperfusion ◽  
Sodium Currents ◽  
Simulated Ischemia
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