The Sarcoplasmic Reticulum and the Evolution of the Vertebrate Heart

Shiels, Holly A.; Galli, Gina L. J.

doi:10.1152/physiol.00015.2014

Cited by 63 publications

(75 citation statements)

References 159 publications

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“…The positive inotropic effects of Ca 2+ and adrenaline are consistent with previous studies on cardiac muscle from snakes and other reptiles (Shiels and Galli, 2014;Zaar et al, 2007), but more importantly, in context of the major aims of the present study, there were few effects of digestion on contractile force. Thus, although mRNA for myosin increases postprandially (Andersen et al, 2005), our study demonstrates that the expression of the contractile proteins is not translated into increased contractile force.…”

Section: Discussionsupporting

confidence: 92%

Improved cardiac filling facilitates the postprandial elevation of stroke volume inPython regius

Enok

Leite

et al. 2016

Journal of Experimental Biology

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To accommodate the pronounced metabolic response to digestion, pythons increase heart rate and elevate stroke volume, where the latter has been ascribed to a massive and fast cardiac hypertrophy. However, numerous recent studies show that heart mass rarely increases, even upon ingestion of large meals, and we therefore explored the possibility that a rise in mean circulatory filling pressure (MCFP) serves to elevate venous pressure and cardiac filling during digestion. To this end, we measured blood flows and pressures in anaesthetized Python regius. The anaesthetized snakes exhibited the archetypal tachycardia as well as a rise in both venous pressure and MCFP that fully account for the approximate doubling of stroke volume. There was no rise in blood volume and the elevated MCFP must therefore stem from increased vascular tone, possibly by means of increased sympathetic tone on the veins. Furthermore, although both venous pressure and MCFP increased during volume loading, there was no evidence that postprandial hearts were endowed with an additional capacity to elevate stroke volume. In vitro measurements of force development of paced ventricular strips also failed to reveal signs of increased contractility, but the postprandial hearts had higher activities of cytochrome oxidase and pyruvate kinase, which probably serves to sustain the rise in cardiac work during digestion.

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Section: Discussionsupporting

confidence: 92%

Improved cardiac filling facilitates the postprandial elevation of stroke volume inPython regius

Enok

Leite

et al. 2016

Journal of Experimental Biology

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“…Expression can increase in response to cold acclimation while activity may increase in response to adrenergic stimulation (reviewed in Shiels and Galli, 2014). Since cold acclimation is also known to increase the dependence of excitation-contraction coupling on SR calcium release in fish cardiomyocytes (Shiels and Galli, 2014), the increased Atp2a2a expression observed after BaP exposure may indicate increased reliance of cardiac contraction on SR calcium stores in the current experiment. Further work is needed to determine the functional consequences of BaP-induced increases in cardiac Atp2a2a expression in zebrafish.…”

Section: Gene Expression Changes After Acute Benzo-a-pyrene Exposurementioning

confidence: 75%

Comparison of the acute effects of benzo-a-pyrene on adult zebrafish (Danio rerio) cardiorespiratory function following intraperitoneal injection versus aqueous exposure

Gerger

Weber

2015

Aquatic Toxicology

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“…Ryanodine receptor expression level in ventricular myocytes, however was 78% lower in D. rerio than in the rabbit and action potential‐induced calcium transients were only 20% mediated by calcium release from the SR (Bovo et al ., ). Instead, calcium transients were mainly mediated by Ca 2+ influx from L‐type Ca 2+ channels and NCX (Bovo et al ., ; Shiels & Galli, ). Our work suggests that this may hold true in the pacemaker cells because of the greater effect of zatebradine on f Hmax .…”

Section: Discussionmentioning

confidence: 97%

Membrane and calcium clock mechanisms contribute variably as a function of temperature to setting cardiac pacemaker rate in zebrafish Danio rerio

Marchant

Farrell

2019

Journal of Fish Biology

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Here, we show that heart rate in zebrafish Danio rerio is dependent upon two pacemaking mechanisms and it possesses a limited ability to reset the cardiac pacemaker with temperature acclimation. Electrocardiogram recordings, taken from individual, anaesthetised zebrafish that had been acclimated to 18, 23 or 28°C were used to follow the response of maximum heart rate (fHmax) to acute warming from 18°C until signs of cardiac failure appeared (up to c. 40°C). Because fHmax was similar across the acclimation groups at almost all equivalent test temperatures, warm acclimation was limited to one significant effect, the 23°C acclimated zebrafish had a significantly higher (21%) peak fHmax and reached a higher (3°C) test temperature than the 18°C acclimated zebrafish. Using zatebradine to block the membrane hyperpolarisation‐activated cyclic nucleotide–gated channels (HCN) and examine the contribution of the membrane clock mechanisms to cardiac pacemaking, f Hmax was significantly reduced (by at least 40%) at all acute test temperatures and significantly more so at most test temperatures for zebrafish acclimated to 28°C vs. 23°C. Thus, HCN channels and the membrane clock were not only important, but could be modified by thermal acclimation. Using a combination of ryanodine (to block sarcoplasmic calcium release) and thapsigargin (to block sarcoplasmic calcium reuptake) to examine the contribution of sarcoplasmic reticular handling of calcium and the calcium clock, f Hmax was again consistently reduced independent of the test temperature and acclimation temperature, but to a significantly lesser degree than zatebradine for zebrafish acclimated to both 28 and 18°C. Thus, the calcium clock mechanism plays an additional role in setting pacemaker activity that was independent of temperature. In conclusion, the zebrafish cardiac pacemaker has a limited temperature acclimation ability compared with known effects for other fishes and involves two pacemaking mechanisms, one of which was independent of temperature.

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The Sarcoplasmic Reticulum and the Evolution of the Vertebrate Heart

Cited by 63 publications

References 159 publications

Improved cardiac filling facilitates the postprandial elevation of stroke volume inPython regius

Improved cardiac filling facilitates the postprandial elevation of stroke volume inPython regius

Comparison of the acute effects of benzo-a-pyrene on adult zebrafish (Danio rerio) cardiorespiratory function following intraperitoneal injection versus aqueous exposure

Membrane and calcium clock mechanisms contribute variably as a function of temperature to setting cardiac pacemaker rate in zebrafish Danio rerio

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