title: Deficiency of testosterone associates with the substrate of atrial fibrillation in the rat model.
abstract: BACKGROUND
  Since the prevalence of atrial fibrillation (AF) increases progressively with aging, especially in men, we hypothesized that testosterone might affect the occurrence of AF.
  
  
  RESULTS
  We examined the electrophysiological properties of the atria in isolated-perfused hearts of sham-operated male (SM), female (SF), orchiectomized male with and without administration of testosterone (ORCH-T and ORCH), and ovariectomized female (OVX) Sprague-Dawley rats. An electrophysiological study revealed that repetitive atrial responses induced by electrical stimuli significantly increased in ORCH rats without changes in other electrophysiological properties and were abolished by administration of testosterone. To investigate the underlying mechanisms, we evaluated the expression level of calcium-handling proteins. In ORCH rats, the immunoreactive protein level of ryanodine receptor type 2 (RyR2) and sodium-calcium exchanger significantly increased as compared with SM and ORCH-T rats without alterations in the level of FK506-binding protein (FKBP12.6), sarcoendoplasmic reticulum Ca-ATPase, and phospholamban. Immunoprecipitation analysis demonstrated decreased binding of FKBP12.6 to RyR2 in ORCH rats, which was prevented by testosterone. In contrast, the expression levels of these proteins showed no significant differences between SF and OVX rats.
  
  
  CONCLUSIONS
  Deficiency of testosterone was arrhythmogenic in rat atria possibly through less binding of FKBP12.6 to RyR2, which could induce feasible calcium leakage from the sarcoendoplasmic reticulum. These results would explain, at least in part, the increase in the prevalence of AF in accordance with the decline of testosterone particularly in elderly men.
authors.affiliation: The Second Department of Internal Medicine, University of Toyama, Toyama, Japan. tkyk1027@med.u-toyama.ac.jp
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tsuneda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamashita
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kato
authors.forename: Akiko
authors.initials: A
authors.lastname: Sekiguchi
authors.forename: Kouichi
authors.initials: K
authors.lastname: Sagara
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sawada
authors.forename: Tadanori
authors.initials: T
authors.lastname: Aizawa
authors.forename: Long-Tai
authors.initials: LT
authors.lastname: Fu
authors.forename: Akira
authors.initials: A
authors.lastname: Fujiki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inoue
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013739:Testosterone / Q000172:deficiency*
chemical_list: D013739:Testosterone