title: Repeated allergen challenge in rats increases vitamin A consumption.
abstract: BACKGROUND
  Vitamin A plays an important role in airways epithelial repair and differentiation. Allergen challenge induces epithelial damage and shedding, which cause an increase in repair activity.
  
  
  OBJECTIVE
  To examine whether repeated allergen challenges could increase vitamin A consumption in a rat model.
  
  
  METHODS
  Allergic bronchitis was induced in 12 animals, and 12 rats remained naive. After 14 days, repeated allergen inhalation challenges were performed in the sensitized rats for 2 weeks. On day 16, allergen challenge was performed and bronchoconstriction was measured in all 24 rats. On day 30, all rats were killed. BAL was performed and ex vivo tumor necrosis factor (TNF)-alpha and nitric oxide (NO) production was measured in the lavage cells. Liver, lung tissue, and serum were collected for measurement of vitamin A concentration.
  
  
  RESULTS
  The study rats showed severe bronchoconstriction after allergen challenge compared to the naive rats, and ex vivo TNF-alpha and NO production was significantly higher in the sensitized rats. Serum and lung concentrations of vitamin A were not different among the two groups. However, the vitamin A liver concentration in the study rats was significantly lower compared to the naive rats.
  
  
  CONCLUSIONS
  We conclude that vitamin A utilization is increased during repeated allergen challenge and allergic bronchitis, most probably due to increased demand for epithelial repair.
authors.affiliation: Pediatric Pulmonology Clinic, Bikur Cholim Hospital, Haddasa Medical School, Jerusalem, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Shoseyov
authors.forename: Haim
authors.initials: H
authors.lastname: Bibi
authors.forename: Hans
authors.initials: H
authors.lastname: Biesalski
authors.forename: Ram
authors.initials: R
authors.lastname: Reifen
mesh_terms: D000485:Allergens; D000818:Animals; D016535:Bronchial Hyperreactivity / Q000378:metabolism* / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D001991:Bronchitis / Q000276:immunology* / Q000378:metabolism*; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D016084:Bronchoconstriction / Q000502:physiology; D004195:Disease Models, Animal; D011336:Probability; D011897:Random Allocation; D051381:Rats; D011914:Rats, Inbred BN; D012016:Reference Values; D012680:Sensitivity and Specificity; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000378:metabolism*; D014801:Vitamin A / Q000032:analysis / Q000378:metabolism*
chemical_list: D000485:Allergens; D014409:Tumor Necrosis Factor-alpha; D014801:Vitamin A