Characterization of corticosteroid redosing in an in vitro cell line model

The purpose of this study was to investigate dexamethasone redosing as function of time and dose. 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. 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. Our results suggest a residual effect of the initial exposure that potentiates redosing, allowing significant dose reductions.