Sex-specific activation of SK current by isoproterenol facilitates action potential triangulation and arrhythmogenesis in rabbit ventricles

Mu Chen, Dechun Yin, Shuai Guo, Dong Zhu Xu, Zhuo Wang, Zhenhui Chen, Michael Rubart-von der Lohe, Shien-Fong Lin, Thomas Everett, James N. Weiss, Peng-Sheng Chen

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2 Citations (Scopus)

Abstract

Key Points: It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+-voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25) more prominently than APD at the level of 80% repolarization (APD80), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+-voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+-voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.

Original languageEnglish (US)
JournalJournal of Physiology
DOIs
StateAccepted/In press - Jan 1 2018

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Isoproterenol
Action Potentials
Rabbits
Apamin
Ventricular Fibrillation
Sex Characteristics
Casein Kinase II
Voltage-Sensitive Dye Imaging
Cardiac Myocytes
Adrenergic Agents
Western Blotting
Calcium

Keywords

  • Ca activated potassium channel
  • Sex dimorphism
  • Ventricular arrhythmias

ASJC Scopus subject areas

  • Physiology

Cite this

@article{5663bdf8b4f74485a28ca577e1f1e386,
title = "Sex-specific activation of SK current by isoproterenol facilitates action potential triangulation and arrhythmogenesis in rabbit ventricles",
abstract = "Key Points: It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+-voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25{\%} repolarization (APD25) more prominently than APD at the level of 80{\%} repolarization (APD80), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+-voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+-voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.",
keywords = "Ca activated potassium channel, Sex dimorphism, Ventricular arrhythmias",
author = "Mu Chen and Dechun Yin and Shuai Guo and Xu, {Dong Zhu} and Zhuo Wang and Zhenhui Chen and {Rubart-von der Lohe}, Michael and Shien-Fong Lin and Thomas Everett and Weiss, {James N.} and Peng-Sheng Chen",
year = "2018",
month = "1",
day = "1",
doi = "10.1113/JP275681",
language = "English (US)",
journal = "Journal of Physiology",
issn = "0022-3751",
publisher = "Wiley-Blackwell",

}

TY - JOUR

T1 - Sex-specific activation of SK current by isoproterenol facilitates action potential triangulation and arrhythmogenesis in rabbit ventricles

AU - Chen, Mu

AU - Yin, Dechun

AU - Guo, Shuai

AU - Xu, Dong Zhu

AU - Wang, Zhuo

AU - Chen, Zhenhui

AU - Rubart-von der Lohe, Michael

AU - Lin, Shien-Fong

AU - Everett, Thomas

AU - Weiss, James N.

AU - Chen, Peng-Sheng

PY - 2018/1/1

Y1 - 2018/1/1

N2 - Key Points: It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+-voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25) more prominently than APD at the level of 80% repolarization (APD80), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+-voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+-voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.

AB - Key Points: It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+-voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25) more prominently than APD at the level of 80% repolarization (APD80), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+-voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+-voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.

KW - Ca activated potassium channel

KW - Sex dimorphism

KW - Ventricular arrhythmias

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U2 - 10.1113/JP275681

DO - 10.1113/JP275681

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JO - Journal of Physiology

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SN - 0022-3751

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