title: Ionic and cellular basis for the predominance of the Brugada syndrome phenotype in males.
abstract: BACKGROUND
  The Brugada syndrome displays an autosomal dominant mode of transmission with low penetrance. Despite equal genetic transmission of the disease, the clinical phenotype is 8 to 10 times more prevalent in males than in females. The basis for this intriguing sex-related distinction is unknown. The present study tests the hypothesis that the disparity in expression of the Brugada phenotype is a result of a more prominent I(to)-mediated action potential notch in the right ventricular (RV) epicardium of males versus females.
  
  
  RESULTS
  We studied epicardial tissue slices, arterially perfused wedge preparations, and dissociated epicardial myocytes isolated from male and female canine hearts. RV epicardium action potential phase 1 amplitude was 64.8+/-2.0% of that of phase 2 in males compared with 73.8+/-4.4% in females (P<0.05) at a cycle length of 2000 ms. I(to) density was 26% smaller and time constant for inactivation 17% smaller at +40 mV in female versus male RV epicardial cells (P<0.05). The other functional characteristics of I(to), including the voltage dependence of inactivation and time course of reactivation, were no different between the sexes. Pinacidil caused loss of action potential dome in male, but not female, RV epicardial tissue slices. Terfenadine (5 micromol/L) induced phase 2 reentry in 6 of 7 male but only 2 of 7 female arterially perfused wedge preparations. Two of 6 male and 1 of 2 female preparations developed polymorphic ventricular tachycardia/ventricular fibrillation.
  
  
  CONCLUSIONS
  Our results suggest that the predominance of the Brugada phenotype in males is a result of the presence of a more prominent I(to) in males versus females.
authors.affiliation: Masonic Medical Research Laboratory, Utica, NY 13501-1787, USA.
authors.forename: José M
authors.initials: JM
authors.lastname: Di Diego
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Cordeiro
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Goodrow
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Fish
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Zygmunt
authors.forename: Guillermo J
authors.initials: GJ
authors.lastname: Pérez
authors.forename: Fabiana S
authors.initials: FS
authors.lastname: Scornik
authors.forename: Charles
authors.initials: C
authors.lastname: Antzelevitch
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D002478:Cells, Cultured; D046508:Culture Techniques; D004285:Dogs; D005260:Female; D006321:Heart / Q000502:physiology; D007700:Kinetics; D008297:Male; D010496:Pericardium / Q000187:drug effects / Q000502:physiology*; D010641:Phenotype; D020110:Pinacidil / Q000494:pharmacology; D012737:Sex Factors; D013577:Syndrome; D016593:Terfenadine / Q000494:pharmacology
chemical_list: D020110:Pinacidil; D016593:Terfenadine