title: [Effects of tibolone on the breast parenchyma: experimental study].
abstract: OBJECTIVE
  To assess the effect of tibolone on mammary tissue of castrated rats over 3 different periods of time.
  
  
  METHODS
  Sixty virgin female Wistar rats were submitted to oophorectomy. Twenty-one days after surgery, with hypoestrogenism confirmed, the experimental rats were randomly assigned to six groups: Tibolone 1 (n=10) received tibolone 1 mg/day for 23 days, tibolone 2 (n=10) for 59 days and tibolone 3 (n=10) for 118 days. The groups control 1 (n=8), control 2 (n=7) and control 2 (n=10) received distilled water for 23, 59 and 118 days, respectively. After treatment, all six pairs of mammary glands were removed and stained with hematoxylin and eosin (HE) for histological analysis after euthanasia. The histological parameters evaluated were: epithelial cell proliferation and secretory activity. The variables were analyzed statistically, with the level of significance set at 0.05.
  
  
  RESULTS
  Histological changes were observed in 20/55 rats, mild epithelial hyperplasia in 7/55, moderate epithelial hyperplasia in 5/55, alveolar-nodular hyperplasia in 7/55, atypia without epithelial proliferation in 1/55, and no cases of severe epithelial hyperplasia were found. Secretory activity was observed in 31/55 rats. The secretory activity was significantly higher in the tibolone groups compared to control at all the time points assessed (p=0,001). The histological changes were did not show significance when the control and tibolone groups were compared. The time of exposure to tibolone did not show significance when the three different periods of evaluation were compared.
  
  
  CONCLUSIONS
  No relation between histological modification and tibolone treatment was verified after short-, medium- and long-term treatment.
authors.affiliation: Faculdade Evangélica do Paraná, Curitiba, PR, Brasil.
authors.forename: Luciana De Oliveira
authors.initials: Lde O
authors.lastname: Marques
authors.affiliation: Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: Luiz Martins
authors.initials: LM
authors.lastname: Collaço
authors.affiliation: Faculdade Evangélica do Paraná, Curitiba, PR, Brasil.
authors.forename: Larson Reichembach
authors.initials: LR
authors.lastname: Pizzatto
authors.affiliation: Faculdade Evangélica do Paraná, Curitiba, PR, Brasil.
authors.forename: Beatriz Badinhani Mota
authors.initials: BB
authors.lastname: Marcondes
mesh_terms: D000818:Animals; D020847:Estrogen Receptor Modulators / Q000494:pharmacology*; D005260:Female; D008321:Mammary Glands, Animal / Q000187:drug effects*; D009652:Norpregnenes / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D020847:Estrogen Receptor Modulators; D009652:Norpregnenes; C027385:tibolone