title: Effect of hormone replacement therapy on lacrimal fluid peroxidase activity in woman.
abstract: OBJECTIVE
  Lacrimal fluid peroxidase (POD) is an antioxidant and antimicrobial enzyme involved in the protection of the ocular surface. Our recent findings showed the existence of significant cyclic variations in POD activity that were positively correlated with those of 17beta-estradiol plasma levels throughout the menstrual cycle of fertile women. During the menopause, women lacrimal fluid POD activity significantly (P<0.05) decreased according to the natural oestrogen reduction. Since a possible influence of oestrogen on human POD activity was suggested, aim of the present investigation is to evaluate whether hormone replacement therapy (HRT) might influence this enzyme activity.
  
  
  METHODS
  Lacrimal fluid POD activities of 10 healthy postmenopausal women (mean age: 52.0) and eight healthy postmenopausal women (mean age: 53.0) treated by oral or transdermal routes containing oestrogen or oestrogen plus progestin were determined. Enzyme activity of each tear sample (5 microl) was spectrophotometrically determined by the 5,5'-dithiobis, 2-nitrobenzoic acid thiocyanate (NBS-SCN) assay; total protein content of tears was determined too. 17beta-Estradiol plasma levels were assayed by ELISA test.
  
  
  RESULTS
  HRT significantly (P<0.05) increased tear POD low postmenopausal levels. The significant (P<0.05) rise of 17beta-estradiol plasma levels of treated women was not strictly correlated to the enzyme activity increase in tears.
  
  
  CONCLUSIONS
  The suggested estrogen regulation of lacrimal fluid POD activity could be one possible cause for the female gender predilection in some ocular diseases. HRT is able to increase tear POD activity levels of postmenopausal women, probably contributing to the effective relieve of ocular surface complications occurring during menopause.
authors.affiliation: Dip Biologia di Base ed Applicata, Coppito1, Università de L'Aquila, Via Vetoio, 67010, L'Aquila, Italy. giordanamarcozzi@hotmail.com
authors.forename: Giordana
authors.initials: G
authors.lastname: Marcozzi
authors.forename: Veronica
authors.initials: V
authors.lastname: Liberati
authors.forename: Federica
authors.initials: F
authors.lastname: Madia
authors.forename: Annalisa
authors.initials: A
authors.lastname: Pizzinga
authors.forename: Giuseppe
authors.initials: G
authors.lastname: de Feo
mesh_terms: D004958:Estradiol / Q000097:blood / Q000378:metabolism*; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D007765:Lacrimal Apparatus / Q000201:enzymology; D008875:Middle Aged; D009195:Peroxidase / Q000378:metabolism*; D017698:Postmenopause / Q000378:metabolism*; D013666:Tears / Q000201:enzymology*
chemical_list: D004958:Estradiol; D009195:Peroxidase