Department of Biology

Aarhus University Seal / Aarhus Universitets segl

Ole Bækgaard Nielsen

Extracellular determinants of cardiac contractility in the cold anoxic turtle

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Extracellular determinants of cardiac contractility in the cold anoxic turtle. / Overgaard, Johannes; Wang, Tobias; Nielsen, Ole Baekgaard; Gesser, Hans.

In: Physiological and Biochemical Zoology, Vol. 78, No. 6, 2005, p. 976-95.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

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Author

Overgaard, Johannes ; Wang, Tobias ; Nielsen, Ole Baekgaard ; Gesser, Hans. / Extracellular determinants of cardiac contractility in the cold anoxic turtle. In: Physiological and Biochemical Zoology. 2005 ; Vol. 78, No. 6. pp. 976-95.

Bibtex

@article{2a8104f0f37311dd8f9a000ea68e967b,
title = "Extracellular determinants of cardiac contractility in the cold anoxic turtle",
abstract = "Painted turtles (Chrysemys picta) survive months of anoxic submergence, which is associated with large changes in the extracellular milieu where pH falls by 1, while extracellular K+, Ca++, and adrenaline levels all increase massively. While the effect of each of these changes in the extracellular environment on the heart has been previously characterized in isolation, little is known about their interactions and combined effects. Here we examine the isolated and combined effects of hyperkalemia, acidosis, hypercalcemia, high adrenergic stimulation, and anoxia on twitch force during isometric contractions in isolated ventricular strip preparations from turtles. Experiments were performed on turtles that had been previously acclimated to warm (25 degrees C), cold (5 degrees C), or cold anoxia (submerged in anoxic water at 5 degrees C). The differences between acclimation groups suggest that cold acclimation, but not anoxic acclimation per se, results in a downregulation of processes in the excitation-contraction coupling. Hyperkalemia (10 mmol L(-1) K+) exerted a strong negative inotropic effect and caused irregular contractions; the effect was most pronounced at low temperature (57%-97% reductions in twitch force). Anoxia reduced twitch force at both temperatures (14%-38%), while acidosis reduced force only at 5 degrees C (15%-50%). Adrenergic stimulation (10 micromol L(-1)) increased twitch force by 5%-19%, but increasing extracellular [Ca++] from 2 to 6 mmol L(-1) had only small effects. When all treatments were combined with anoxia, twitch force was higher at 5 degrees C than at 25 degrees C, whereas in normoxia twitch force was higher at 25 degrees C. We propose that hyperkalemia may account for a large part of the depressed cardiac contractility during long-term anoxic submergence.",
keywords = "Acclimatization, Adenosine Triphosphatases, Analysis of Variance, Animals, Anoxia, Calcium, Electric Stimulation, Epinephrine, Myocardial Contraction, Potassium, Temperature, Turtles",
author = "Johannes Overgaard and Tobias Wang and Nielsen, {Ole Baekgaard} and Hans Gesser",
year = "2005",
doi = "10.1086/432853",
language = "English",
volume = "78",
pages = "976--95",
journal = "Physiological and Biochemical Zoology",
issn = "1522-2152",
publisher = "University of Chicago Press",
number = "6",

}

RIS

TY - JOUR

T1 - Extracellular determinants of cardiac contractility in the cold anoxic turtle

AU - Overgaard, Johannes

AU - Wang, Tobias

AU - Nielsen, Ole Baekgaard

AU - Gesser, Hans

PY - 2005

Y1 - 2005

N2 - Painted turtles (Chrysemys picta) survive months of anoxic submergence, which is associated with large changes in the extracellular milieu where pH falls by 1, while extracellular K+, Ca++, and adrenaline levels all increase massively. While the effect of each of these changes in the extracellular environment on the heart has been previously characterized in isolation, little is known about their interactions and combined effects. Here we examine the isolated and combined effects of hyperkalemia, acidosis, hypercalcemia, high adrenergic stimulation, and anoxia on twitch force during isometric contractions in isolated ventricular strip preparations from turtles. Experiments were performed on turtles that had been previously acclimated to warm (25 degrees C), cold (5 degrees C), or cold anoxia (submerged in anoxic water at 5 degrees C). The differences between acclimation groups suggest that cold acclimation, but not anoxic acclimation per se, results in a downregulation of processes in the excitation-contraction coupling. Hyperkalemia (10 mmol L(-1) K+) exerted a strong negative inotropic effect and caused irregular contractions; the effect was most pronounced at low temperature (57%-97% reductions in twitch force). Anoxia reduced twitch force at both temperatures (14%-38%), while acidosis reduced force only at 5 degrees C (15%-50%). Adrenergic stimulation (10 micromol L(-1)) increased twitch force by 5%-19%, but increasing extracellular [Ca++] from 2 to 6 mmol L(-1) had only small effects. When all treatments were combined with anoxia, twitch force was higher at 5 degrees C than at 25 degrees C, whereas in normoxia twitch force was higher at 25 degrees C. We propose that hyperkalemia may account for a large part of the depressed cardiac contractility during long-term anoxic submergence.

AB - Painted turtles (Chrysemys picta) survive months of anoxic submergence, which is associated with large changes in the extracellular milieu where pH falls by 1, while extracellular K+, Ca++, and adrenaline levels all increase massively. While the effect of each of these changes in the extracellular environment on the heart has been previously characterized in isolation, little is known about their interactions and combined effects. Here we examine the isolated and combined effects of hyperkalemia, acidosis, hypercalcemia, high adrenergic stimulation, and anoxia on twitch force during isometric contractions in isolated ventricular strip preparations from turtles. Experiments were performed on turtles that had been previously acclimated to warm (25 degrees C), cold (5 degrees C), or cold anoxia (submerged in anoxic water at 5 degrees C). The differences between acclimation groups suggest that cold acclimation, but not anoxic acclimation per se, results in a downregulation of processes in the excitation-contraction coupling. Hyperkalemia (10 mmol L(-1) K+) exerted a strong negative inotropic effect and caused irregular contractions; the effect was most pronounced at low temperature (57%-97% reductions in twitch force). Anoxia reduced twitch force at both temperatures (14%-38%), while acidosis reduced force only at 5 degrees C (15%-50%). Adrenergic stimulation (10 micromol L(-1)) increased twitch force by 5%-19%, but increasing extracellular [Ca++] from 2 to 6 mmol L(-1) had only small effects. When all treatments were combined with anoxia, twitch force was higher at 5 degrees C than at 25 degrees C, whereas in normoxia twitch force was higher at 25 degrees C. We propose that hyperkalemia may account for a large part of the depressed cardiac contractility during long-term anoxic submergence.

KW - Acclimatization

KW - Adenosine Triphosphatases

KW - Analysis of Variance

KW - Animals

KW - Anoxia

KW - Calcium

KW - Electric Stimulation

KW - Epinephrine

KW - Myocardial Contraction

KW - Potassium

KW - Temperature

KW - Turtles

U2 - 10.1086/432853

DO - 10.1086/432853

M3 - Journal article

C2 - 16228937

VL - 78

SP - 976

EP - 995

JO - Physiological and Biochemical Zoology

JF - Physiological and Biochemical Zoology

SN - 1522-2152

IS - 6

ER -