title: Characterization of corticosteroid redosing in an in vitro cell line model.
abstract: OBJECTIVE
  The purpose of this study was to investigate dexamethasone redosing as function of time and dose.
  
  
  METHODS
  We studied the effect of 48 hours' exposure to various concentrations of dexamethasone in a human pulmonary adenocarcinoma cell line (H-441). We measured the level of surfactant protein B (SP-B) mRNA by quantitative reverse transcription-PCR after initial dexamethasone exposure, and after redosing, 1 or 2 weeks later. Values are mean +/- SE for 5 experiments. Comparisons were made by Mann-Whitney and Kruskal-Wallis test with significance set at P < .05.
  
  
  RESULTS
  Induction of SP-B mRNA was maximal within 48 hours of the initial dexamethasone exposure. Redosing with the same dexamethasone concentration resulted in levels more than double those initially observed. Redosing with dexamethasone concentration 10 times lower had an effect comparable to that of the initial, higher concentration.
  
  
  CONCLUSIONS
  Our results suggest a residual effect of the initial exposure that potentiates redosing, allowing significant dose reductions.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Gynecology and Obstetrics, University of Texas Medical School at Houston, 6431 Fannin, Houston, TX 77030, USA. alex.c.vidaeff@uth.tmc.edu
authors.forename: Alex C
authors.initials: AC
authors.lastname: Vidaeff
authors.forename: Susan M
authors.initials: SM
authors.lastname: Ramin
authors.forename: Larry C
authors.initials: LC
authors.lastname: Gilstrap
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Alcorn
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology; D045744:Cell Line, Tumor / Q000187:drug effects; D003907:Dexamethasone / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005938:Glucocorticoids / Q000008:administration & dosage*; D006801:Humans; D008168:Lung; D008175:Lung Neoplasms / Q000473:pathology; D016133:Polymerase Chain Reaction; D037701:Pulmonary Surfactant-Associated Protein B / Q000187:drug effects* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D005938:Glucocorticoids; D037701:Pulmonary Surfactant-Associated Protein B; D012333:RNA, Messenger; D003907:Dexamethasone