title: Smoking is associated with remodeling of gap junction in the rat heart: smoker's paradox explanation?
abstract: BACKGROUND
  In a previous study utilizing the rat model, exposure to tobacco smoke for 5 weeks increased survival after AMI, despite similar age and infarct size between the smokers and nonsmokers, and absence of reperfusion.
  
  
  OBJECTIVE
  Thus, this study aimed to analyze the effects of exposure to tobacco smoke on intensity, distribution or phosphorylation of connexin 43 in the rat heart.
  
  
  METHODS
  Wistar rats weighing 100 g were randomly allocated into 2 groups: 1) CONTROL (n = 25); 2) Exposed to tobacco smoke (ETS), n = 23. After 5 weeks, left ventricular morphometric analysis, immunohistochemistry and western blotting for connexin 43 (Cx43) were performed.
  
  
  RESULTS
  Collagen volume fraction, cross-sectional areas, and ventricular weight were not statistically different between control and ETS. ETS showed lower stain intensity of Cx43 at intercalated disks (
  
  
  METHODS
  2.32 ± 0.19; ETS: 1.73 ± 0.18; p = 0.04). The distribution of CX43 at intercalated disks did not differ between the groups (
  
  
  METHODS
  3.73 ± 0.12; ETS: 3.20 ± 0.17; p = 0.18). ETS rats showed higher levels of dephosphorylated form of Cx43 (CONTROL: 0.45 ± 0.11; ETS: 0.90 ± 0.11; p = 0.03). On the other hand, total Cx43 did not differ between control and ETS groups (
  
  
  METHODS
  0.75 ± 0.19; ETS: 0.93 ± 0.27; p = 0.58).
  
  
  CONCLUSIONS
  Exposure to tobacco smoke resulted in cardiac gap junction remodeling, characterized by alterations in the quantity and phosphorylation of the Cx43, in rats hearts. This finding could explain the smoker's paradox observed in some studies.
authors.affiliation: Faculdade de Medicina de Botucatu, Botucatu, SP – Brazil.
authors.forename: Rosangela
authors.initials: R
authors.lastname: Novo
authors.forename: Cristiana M
authors.initials: CM
authors.lastname: Freire
authors.forename: Sergio
authors.initials: S
authors.lastname: Felisbino
authors.forename: Marcos F
authors.initials: MF
authors.lastname: Minicucci
authors.forename: Paula S
authors.initials: PS
authors.lastname: Azevedo
authors.forename: Leonardo A M
authors.initials: LA
authors.lastname: Zornoff
authors.forename: Sergio A R
authors.initials: SA
authors.lastname: Paiva
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018031:Connexin 43 / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism*; D007150:Immunohistochemistry; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D023421:Models, Animal; D009203:Myocardial Infarction / Q000517:prevention & control*; D010766:Phosphorylation; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D018031:Connexin 43; D014028:Tobacco Smoke Pollution