Unique excitation–contraction characteristics of mouse myocardium as revealed by SEA0400, a specific inhibitor of Na+–Ca2+ exchanger

Tanaka, Hikaru; Namekata, Iyuki; Takeda, Kentaro; Kazama, Akihiro; Shimizu, Yoshiko; Moriwaki, Rina; Hirayama, Wataru; Sato, Akira; Kawanishi, Toru; Shigenobu, Koki

doi:10.1007/s00210-005-1051-9

Cited by 37 publications

(40 citation statements)

References 22 publications

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“…However, in the range of physiological heart rates (200-600 bpm, or 3.3-10 Hz), the contraction amplitude showed no detectable frequency dependence. This observation conforms with the other reports that showed the negative force-frequency relationship of mouse heart muscle, which developed only at stimulation frequencies lower than 1-2 Hz [22,23].…”

Section: Properties Of the Isolated Heart Cellssupporting

confidence: 93%

“…4A. The contraction had an amplitude of 8.2 ± 2.2% (n = 8) of the resting cell length at a stimulation frequency of 300 bpm, and was larger at lower stimulation frequency (16.5 ± 1.6% at 60 bpm), being consistent with the negative force-frequency relation known for the heart muscle of the mouse [17,19,22,23]. However, in the range of physiological heart rates (200-600 bpm), the contraction amplitude showed no significant frequency-dependence (p = 0.47 by one-way ANOVA).…”

Section: Contraction Properties Of the Cellssupporting

confidence: 79%

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A Simple Technique for Isolating Healthy Heart Cells from Mouse Models

Shioya

2007

J. Physiol. Sci

128

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Single heart cells of mouse models provide powerful tools for heart research. However, their isolation is not easy, and it imposes a significant bottleneck on their use in cellular studies of the heart. Aiming to overcome this problem, this report introduces a novel technique that reproducibly isolates healthy heart cells from mouse models. Using simple devices that ensure easy handling and the rapid aortic cannulation of a small mouse heart, cell isolation was done under physiological conditions without using the "KB" medium or 2,3-butanedione monoxime (BDM). The isolated cells consistently had a healthy appearance and a high viability of 75 ± 5% (mean ± SD) in Tyrode solution containing 1.8 mM Ca 2+ . After 8 h of storage at 37°C, they still had a viability of 45 ± 12%. The cells showed normal contraction properties when field-stimulated, and they generated normal action potentials and membrane currents under the whole-cell clamp condition. The β-adrenergic signal transduction of the cells was also normal when it was examined with the isoproterenol enhancement of the L-type Ca 2+ current.Key words: mouse, cardiac myocyte, contraction, action potential, ionic current.Single heart cells of mouse models provide powerful tools for heart research. In these cells, one can take advantage of the versatility of recent genetic engineering technology [1] and also of the accuracy of single-cell measurement techniques such as patch-clamp and Ca 2+ imaging. So far, molecular mechanisms of fundamental heart functions, such as excitation-contraction coupling, action potential shaping, and β-adrenergic signaling, have been successfully unveiled by using single heart cells of mouse models [2][3][4][5][6][7]. Moreover, these cells also provide a convenient platform for analyzing pathogenic mechanisms and the pathophysiology of hereditary heart diseases in molecular detail [8,9].For such single-cell studies, healthy heart cells are absolutely necessary; however, their isolation from mouse models is not easy. Surgery and aortic cannulation of a small mouse heart are hard to do and require a long time, and during that time, the heart suffers from complete ischemia. Consequently, the cells isolated from these hearts show various signs of ischemic damages, such as bizarre appearance, low viability levels, and abnormalities in their excitation and contraction properties. Cells of these kinds are hard to use for the experiment, and the data they provide are often difficult to interpret. This issue imposes a significant bottleneck on the use of mouse heart cells and is especially problematic in genetically engineered mouse models that are usually available only in limited amounts.To solve this problem, two major work-arounds have been devised and used for heart cell isolation from mouse models. One is to incubate the cells in high-K + , Ca 2+ -free "KB" medium at 4°C [10,11], and the other is to administer 10-20 mM 2,3-butanedione monoxime (BDM) in the media for cell isolation and storage [12,13]. Both workarounds proved to be...

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Section: Properties Of the Isolated Heart Cellssupporting

confidence: 93%

Section: Contraction Properties Of the Cellssupporting

confidence: 79%

A Simple Technique for Isolating Healthy Heart Cells from Mouse Models

Shioya

2007

J. Physiol. Sci

128

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“…Mitoxantrone, however, produced stronger increases in developed tension at lower stimulation frequencies in the present study, whereas a known inhibitor of the Na + -Ca 2+ exchange system, SEA0400, has been shown to produce a stronger increase in developed tension at higher stimulation frequencies in isolated ventricular muscle preparations obtained from mouse hearts [26]. These effects are expected because an inhibition of the Na + -Ca 2+ exchange system would elevate intracellular Ca 2+ concentrations more at higher stimulation frequencies when greater amounts of Ca 2+ enter the cells through the slow Ca 2+ channels [5,34].…”

Section: Discussioncontrasting

confidence: 79%

Mechanisms Responsible for Reduced Cardiotoxicity of Mitoxantrone Compared to Doxorubicin Examined in Isolated Guinea-Pig Heart Preparations

et al. 2008

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ABSTRACT. We reported previously that doxorubicin, an anticancer agent that has an anthracycline structure, alters Ca 2+ releasing and uptake mechanisms in the sarcoplasmic reticulum of myocardial cells. These effects of doxorubicin are apparently related to its cardiotoxicity. Mitoxantrone is a similar anticancer agent with an anthracenedion structure that has been shown to be significantly less cardiotoxic. In the present study, the effects of mitoxantrone on the functions of the sarcoplasmic reticulum were examined in isolated muscle preparations obtained from the guinea-pig heart. In electrically-stimulated left atrial muscle preparations, incubation in vitro for 4 hr with 30 or 100 µM mitoxantrone significantly prolonged the time to the peak of twitch tension, markedly increased the developed tension observed at lower stimulation frequencies, thereby attenuating the slope of positive force-frequency relationships, and increased the postrest contraction observed after a 60-sec quiescent period. In myocytes isolated from ventricular muscles, 30 µM mitoxantrone increased the peak and the size of intracellular Ca 2+ concentrations ([Ca 2+ ]i), and prolonged the time to peak [Ca 2+ ]i. In skinned muscle fiber preparations obtained from the left ventricular muscle, 30 µM mitoxantrone significantly increased the caffeine-induced contraction without affecting the Ca 2+ sensitivity of contractile proteins. These results suggest that mitoxantrone enhances Ca 2+ release from the sarcoplasmic reticulum in isolated atrial muscle preparations obtained from the guinea-pig heart. Apparent enhancement of the sarcoplasmic reticulum functions, in contrast to anthracyclines that has been shown to suppress these functions, seems to explain the relative lack of marked cardiotoxicity of mitoxantrone. KEY WORDS: caffeine-induced contraction, Ca 2+ release and uptake by sarcoplasmic reticulum, inotropic effects, intracellular Ca 2+ concentration, mitoxantrone.J. Vet. Med. Sci. 70(3): 255-264, 2008 Anthracyclines are efficacious anti-tumor agents; however, their clinical usefulness is limited by serious cardiotoxic effects. Mitoxantrone, an anthracenedion derivative, has been synthesized in an attempt to develop an agent that has a reliable anticancer activity without the compromising cardiotoxic effects [9,35].Human as well as animal studies demonstrated that the cardiotoxic effects of mitoxantrone are significantly less severe at clinically equivalent anticancer doses compared to those observed with anthracyclines [2,9,11,13,20,22,33].We reported previously [7] that in vivo treatment of rats with doxorubicin results in a prolongation of the time to the peak of twitch tension, a reduction of the developed tension observed at lower stimulation frequencies and an attenuation of the postrest contraction (contraction that is evoked by the first stimulus after a brief quiescent period) observed in electrically-stimulated heart muscle preparations obtained from the drug-treated animals. These changes developed slowly with time aft...

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“…Sustained positive inotropy is observed in the rabbit, guinea pig, and rat ventricle, but in the guinea pig and rat, a transient decrease in contractile force is observed before the increase. The mouse ventricle shows a sustained negative inotropy in response to α-adrenoceptor stimulation (26) that is accompanied by decreased calcium transient amplitude (27). Electrophysiological and pharmacological analysis revealed that α-adrenoceptor stimulation activates the Na + /Ca 2+ exchanger and decreases the Ca 2+ released from the sarcoplasmic reticulum (28).…”

Section: Sympathetic Regulationmentioning

confidence: 99%

New Aspects for the Treatment of Cardiac Diseases Based on the Diversity of Functional Controls on Cardiac Muscles: Diversity in the Excitation–Contraction Mechanisms of the Heart

et al. 2009

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Abstract. The waveform of the myocardial action potential (AP) triggering contraction differs among the species, developmental stage, and pathological state. The species difference in heart rate, which inversely correlates with body size, originates in the ion-channel mechanisms responsible for diastolic depolarization of the sinoatrial node. In some cases, such as the chronically AV-blocked dog and 11-to 13-day chick embryo, the repolarization reserve is decreased making the heart useful for drug evaluation. The degree of dependence of contraction on sarcoplasmic reticulum (SR) function increases during development. The large SR dependence and short AP of the adult mouse and rat support their rapid contraction under high heart rate. The function of the Na + /Ca 2+ exchanger is affected by AP waveform and ion concentrations; its major role is Ca 2+ extrusion, but under pathological conditions such as ischemia-reperfusion, it allows Ca 2+ influx and leads to myocardial injury, including loss of mitochondrial function. The role of mitochondria in ATP supply is less in the fetus where glycolysis plays a greater role. The pharmacological properties of the myocardium are affected by all of these factors and also by autonomic innervation and the hormonal status. Such comprehensive understanding is indispensable for the development of novel therapeutic strategies.

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Unique excitation–contraction characteristics of mouse myocardium as revealed by SEA0400, a specific inhibitor of Na+–Ca2+ exchanger

Cited by 37 publications

References 22 publications

A Simple Technique for Isolating Healthy Heart Cells from Mouse Models

A Simple Technique for Isolating Healthy Heart Cells from Mouse Models

Mechanisms Responsible for Reduced Cardiotoxicity of Mitoxantrone Compared to Doxorubicin Examined in Isolated Guinea-Pig Heart Preparations

New Aspects for the Treatment of Cardiac Diseases Based on the Diversity of Functional Controls on Cardiac Muscles: Diversity in the Excitation–Contraction Mechanisms of the Heart

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