Cellular mechanism of the relationship between myocardial force and frequency of contractions

Lewartowski, B; Pytkowski, B

doi:10.1016/0079-6107(87)90005-8

Cited by 61 publications

(40 citation statements)

References 96 publications

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“…Consequently, efficient adjustments of cardiac output in response to xenobiotics, achieved by changes in stroke volume and/or heart rate are crucial. Cardiac stroke volume is determined by the regulation of myocardial contractility, which depends on the complex regulation of intracellular calcium ([Ca 2+ ] i ) homeostasis on a beat-to-beat basis (Lewartowski and Pytkowski, 1987;Bers, 2001).…”

Section: Discussionmentioning

confidence: 99%

Effects of the organophosphorus pesticide Folisuper 600 (methyl parathion) on the heart function of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802)

et al. 2015

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The aim of this work was to evaluate whether the heart function of bullfrog tadpoles (25 Gosner stage) is affected by their acute exposure (48 h) to a sub-lethal concentration (10 µg.L -1 ) of the active principle of the organophosphorus pesticide Folisuper 600R (methyl parathion -MP). Our results demonstrated that MP causes not only a reduction in tadpoles' cardiac ventricular mass, resulting in a marked reduction in their cardiac twitch force, but also impairs their swimming performance, irrespective of increasing their heart rate. Together, these findings indicate that low and realistic concentration of MP have a negative impact on tadpoles' performance, jeopardizing their survival. Keywords: methyl parathion, cardiac performance, bullfrog tadpoles, Lithobates catesbeianus (Rana catesbeiana).Efeitos do pesticida organofosforado Folisuper 600 (metil paration) sobre a função cardíaca de girinos de rã-touro, Lithobates catesbeianus (Shaw, 1802) ResumoO objetivo do presente estudo foi avaliar se a função cardíaca de girinos de rãs-touro (estágio 25 de Gosner) é afetada pela exposição aguda (48h) a uma concentração sub-letal (10 µg.L -1 ) do princípio ativo do pesticida organofosforado Folisuper 600R (metil paration -MP). Nossos resultados demonstraram que o MP ocasionou não apenas uma redução na massa ventricular cardíaca dos girinos, como também provocou uma redução na sua força de contração cardíaca e de seu desempenho natatório, a despeito de ter sido observado um aumento de sua freqüência cardíaca. Conjuntamente, os achados aqui obtidos indicam que uma baixa e realística concentração de MP exerce um impacto negativo sobre o desempenho dos girinos, ameaçando sua sobrevivência.Palavras-chave: metil paration, desempenho cardíaco, girinos de rã-touro, Lithobates catesbeianus (Rana Catesbeiana).

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Section: Discussionmentioning

confidence: 99%

Effects of the organophosphorus pesticide Folisuper 600 (methyl parathion) on the heart function of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802)

et al. 2015

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“…These data do not necessarily reflect a direct relationship between the positive and negative inotropic effects with sympathetic and vagus nerve stimulation, respectively, as the heart rate was allowed to change with autonomic stimulation. A positive forcefrequency relationship (Bowditch effect) has been shown in the rabbit (Lewartowski & Pytkowski, 1987) and the observed left ventricular pressure changes may be the result of change in the intrinsic heart rate with autonomic stimulation. Nonetheless, these data show that this in vitro preparation responds in a similar fashion to in vivo preparations and is therefore a good model on which further studies of the effects of autonomic stimulation on ventricular inotropy could be conducted.…”

Section: Direct Autonomic Stimulation On the Force Of Left Ventriculamentioning

confidence: 99%

Effects of Direct Sympathetic and Vagus Nerve Stimulation on the Physiology of the Whole Heart – A Novel Model of Isolated Langendorff Perfused Rabbit Heart with Intact Dual Autonomic Innervation

Brack

Coote

2001

Experimental Physiology

127

143

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It is well recognised that stimulation of the sympathetic nervous system exerts a positive chronotropic effect on the heart, speeding the rate of discharge of the intrinsic pacemaker, which is usually the sino-atrial node, whilst parasympathetic stimulation has opposite effects (Levy & Zieske, 1969). Atrioventricular (AV) conduction is also affected, with sympathetic stimulation speeding conduction (positive dromotropy) and parasympathetic stimulation delaying conduction (negative dromotropy) (Warner et al. 1986). Autonomic stimulation also affects myocardial mechanical performance but the cause of this effect is less straightforward. Whilst it is generally accepted that sympathetic stimulation exerts a positive inotropic effect on the heart with increased contractility, the effect of vagal stimulation on cardiac mechanical performance is less well defined (Xenopoulos & Applegate, 1994). At the molecular level, the sympathetic and parasympathetic nervous systems modulate cardiac function by means of the neurotransmitters, catecholamines and acetylcholine, respectively (Levy, 1997), interacting with receptors located on the sarcolemma of the cardiac myocyte. The cellular mechanisms by which stimulation of the autonomic nervous system affect the various processes involved in excitation-contraction coupling have not been fully investigated. The ability to investigate how nerves influence these mechanisms is limited by the type of preparation available.Experimental data relating to the effect of autonomic nerve activity on cardiac function have been obtained in vivo where direct stimulation of autonomic nerves may be confounded by influences from circulating hormones and haemodynamic reflexes. On the other hand, in vitro studies on isolated heart preparations have used exogenous pharmacological agents and chemical analogues, such as isoprenaline, to mimic stimulation of autonomic nerves. The disadvantage of both of these approaches may be overcome by an isolated heart preparation in which both sets of autonomic nerves are intact and available for stimulation. In this paper we describe a novel, isolated Langendorff perfused rabbit heart preparation with intact dual autonomic innervation that allows the study of the effects of direct sympathetic and vagus nerve stimulation on the physiology of the whole heart. To demonstrate the viability of the preparation, we have described the effects of direct stimulation of the sympathetic outflow and vagus nerves on the intrinsic heart rate and AV conduction at varying stimulus strengths and frequencies.Effects of direct sympathetic and vagus nerve stimulation on the physiology of the whole heart -a novel model of isolated Langendorff perfused rabbit heart with intact dual autonomic innervation A novel isolated Langendorff perfused rabbit heart preparation with intact dual autonomic innervation is described. This preparation allows the study of the effects of direct sympathetic and vagus nerve stimulation on the physiology of the whole heart. These hearts (n = 10) had baseline h...

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“…tension rises with increasing frequencies, with the notable exception of the rat ventricle, which exhibits a negative staircase. The cellular mechanism involved in this inotropic response is still the topic of numerous studies (Lewartowski & Pytkowski, 1987;Bers, 1991) which have pointed out that Ca2+ uptake by the sarcoplasmic reticulum (SR) is essential for the occurrence of the staircase (Bers, 1991). Definite experimental evidence for this hypothesis has lagged because of the absence of specific SR Ca pump inhibitors.…”

Section: Introductionmentioning

confidence: 99%

Differential effects of tert‐butyl‐benzohydroquinone, a putative SR Ca²⁺ pump inhibitor, on isometric relaxation during the staircase in the rabbit and rat ventricle

Baudet

Khammari

Noireaud

et al. 1996

British J Pharmacology

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1 The effects of 2,5 di-(tert-butyl)-1,4-benzohydroquinone (TBQ), a putative inhibitor of the sarcoplasmic reticulum Ca21 pump, on mechanical relaxation and contraction-relaxation coupling have been studied at different frequencies (0.5-3 Hz) in isometrically contracting isolated right ventricular preparations of rabbit and rat at 370C. Two types of mechanical responses have been studied: the twitch tension and the force transient (rewarming spike, RSp) following a rapid cooling contracture (RCC, an index of sarcoplasmic reticulum Ca2+ content) on return to 370C. 2 The coupling between contraction and relaxation was assessed by two methods: (a) by evaluation of the variation of the slope relating the maximal rate of tension fall to twitch peak tension; (b) by modelling the twitch according to the following equation: TwT (t) = C x (t/A)B x exp(l -(t/AB) where TwT(t) is the time course of isometric tension, t is time, C and A are an inotropic and a chronotropic index respectively and B, a contraction-relaxation coupling index (Nwasokwa, 1993). 3 In the rabbit ventricle, 30 gM TBQ did not prevent the frequency-induced shortening of the twitch time to half-relaxation (tl/2) and of the time constant (T) describing the final part of the RSp relaxation (r decreased from 140 ms (0.5 Hz) to 133 ms (3 Hz) in control and from 253 ms (0.5 Hz) to 197ms (3Hz) after exposure to TBQ). By contrast, at a given frequency, the prolongation of relaxation induced by TBQ was proportional to its inotropic effect (unchanged slopes and B values) but TBQ did not prevent the acceleration of relaxation observed at high frequencies: B increased from 2.02 (0.5 Hz) to a peak value of 2.18 (1 Hz) in control and from 1.88 (0.5 Hz) to a maximum of 2.48 (2 Hz) after TBQ exposure. TBQ significantly attenuated the decay of RCCs elicited after increasingly longer periods of muscle quiescence as normally observed in control conditions. 4 In the rat ventricle, TBQ depressed relaxation more than expected on the basis of its negative inotropic effects (B decreased from 2.16 to 1.84 at 0.5 Hz and from 2.15 to 1.66 at 3 Hz). TBQ also slowed the rate of RSp relaxation (T increased from 95 ms to 168 ms at 0.5 Hz, and from 109 ms to 149 ms at 3 Hz) and increased twitch tl/2. By contrast with the results obtained in the rabbit ventricle, B, T and t1/2 were frequency-insensitive whether or not TBQ was present. 5 TBQ exerts negative inotropic effects consistent with inhibition of the SR Ca2+ pump. In the rabbit ventricle, the TBQ-induced potentiation of relaxation acceleration at high pacing frequencies suggests the involvement of counteracting Ca2+-mediated mechanisms probably via Ca2+ -calmodulin-activated kinases. In the rat ventricle, TBQ did not have any differential effect on relaxation depending on the frequency, probably because the extent of the negative staircase was small in the present experimental conditions.

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Cellular mechanism of the relationship between myocardial force and frequency of contractions

Cited by 61 publications

References 96 publications

Effects of the organophosphorus pesticide Folisuper 600 (methyl parathion) on the heart function of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802)

Effects of the organophosphorus pesticide Folisuper 600 (methyl parathion) on the heart function of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802)

Effects of Direct Sympathetic and Vagus Nerve Stimulation on the Physiology of the Whole Heart – A Novel Model of Isolated Langendorff Perfused Rabbit Heart with Intact Dual Autonomic Innervation

Differential effects of tert‐butyl‐benzohydroquinone, a putative SR Ca²⁺ pump inhibitor, on isometric relaxation during the staircase in the rabbit and rat ventricle

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Cellular mechanism of the relationship between myocardial force and frequency of contractions

Cited by 61 publications

References 96 publications

Effects of the organophosphorus pesticide Folisuper 600 (methyl parathion) on the heart function of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802)

Effects of the organophosphorus pesticide Folisuper 600 (methyl parathion) on the heart function of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802)

Effects of Direct Sympathetic and Vagus Nerve Stimulation on the Physiology of the Whole Heart – A Novel Model of Isolated Langendorff Perfused Rabbit Heart with Intact Dual Autonomic Innervation

Differential effects of tert‐butyl‐benzohydroquinone, a putative SR Ca2+ pump inhibitor, on isometric relaxation during the staircase in the rabbit and rat ventricle

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Differential effects of tert‐butyl‐benzohydroquinone, a putative SR Ca²⁺ pump inhibitor, on isometric relaxation during the staircase in the rabbit and rat ventricle