Hibernator Citellus undulatus maintains safe cardiac conduction and is protected against tachyarrhythmias during extreme hypothermia: Possible role of Cx43 and Cx45 up-regulation

Vadim V. Fedorov, Li Li, Alexey Glukhov, Irina Shishkina, Rubin R. Aliev, Tatiana Mikheeva, Vladimir P. Nikolski, Leonid V. Rosenshtraukh, Igor R. Efimov*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Background: Most mammals experience cardiac arrest during hypothermia. In contrast, hibernators remain in sinus rhythm even at body temperatures of 0°C. Objectives: The purpose of this study was to quantify electrical activity and connexin expression in the heart of hibernating Siberian ground squirrel Citellus undulatus. Methods: Optical imaging and microelectrode recordings were conducted in Langendorff-perfused hearts and isolated papillary muscles of summer active (SA, n = 19), winter hibernating (WH, n = 21), interbout arousal (IBA, n = 12), and winter active (WA, n = 3) ground squirrels and rabbits (n = 14) at temperatures from + 37°C to + 3°C. Results: All studied SA and WH hearts maintained spontaneous sinus rhythm, safe propagation through the entire conduction system, and normal pattern of ventricular excitation at all temperatures. However, three of the seven IBA and all rabbit hearts lost excitability at 10°C ± 1°C and 12°C ± 1°C, respectively. In WH, SA, and IBA ground squirrels, temperature reduction from 37°C to 3°C resulted in a 10-fold slowing of ventricular conduction velocity and increased excitation threshold. At any temperature, WH ventricles had faster conduction velocity and lower excitation threshold compared with SA and IBA. Immunolabeling demonstrated that connexin43 (Cx43) was significantly up-regulated in WH and WA compared with SA myocardium: Cx43 area density was 12.4 ± 1.3, 15.0 ± 3.0 and 8.6 ± 1.1 μm2/1,000 μm2, respectively. Moreover, Cx45 was expressed in the WH but not in the SA or WA ventricles. Conclusion: Hibernator Citellus undulatus has evolved to maintain safe conduction at extreme hypothermia via up-regulation of Cx43 and Cx45 in order to protect the heart against arrhythmia associated with hypothermia.

Original languageEnglish (US)
Pages (from-to)966-975
Number of pages10
JournalHeart rhythm
Volume2
Issue number9
DOIs
StatePublished - Sep 2005
Externally publishedYes

Keywords

  • Conduction velocity
  • Connexin
  • Hibernation
  • Hypothermia
  • Immunohistochemistry
  • Optical mapping
  • Ventricular fibrillation

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

Fingerprint

Dive into the research topics of 'Hibernator Citellus undulatus maintains safe cardiac conduction and is protected against tachyarrhythmias during extreme hypothermia: Possible role of Cx43 and Cx45 up-regulation'. Together they form a unique fingerprint.

Cite this