OBJECTIVETo observe the effect of three-stage sequential method (TSSM) on interleukin-5 (IL-5) mRNA expression in the lung tissue of asthmatic rat model treated with steroid.

METHODSSD rats were randomly divided into 8 groups, the normal control group (GA), the model group (GB), the model with steroid intervention group (GC) and the 5 treated groups (GD - GH). Excepting those in the GA, all rats were established into the asthma model and rats in GC-GH were intervened by dexamethasone, with the dosage reduced by 0.1 mg/kg per week starting from the 3rd week and withdrawn completely till the 7th week. At the same time, rats in GD - GH were treated with TSSM, and the 1st, 2nd and 3rd recipe of TSSM, as well as pulmicort respules (as positive control) respectively. IL-5 mRNA expression in the lung tissue of rats was detected at different time points by in situ hybridization.

RESULTSComparisons of GD with other groups in IL-5 mRNA expression showed: it was remarkably lowered than that in GB and GC at all time points (P < 0.01); compared to GH, the difference was insignificant at the end of the 2nd week, but significant at the end of the 7th and 9th week (P < 0.01); as for the difference between GD with GE, GF and GG, it showed very significant difference (P < 0.01) at all the time points besides that at the end of the 2nd week, it showed insignificance to GE (P > 0.05) and significance to GF (P < 0.05). The dynamic changes of IL-5 mRNA expression in GD during the steroid withdrawal period showed the lowering was more significantly at the end of the 7th and 9th week than that at the end of the 2nd week (P < 0.05, P < 0.01), but its levels were equal at the former two time points; its lowest level appeared at the end of the 9th week, which approaching the level in GA (P > 0.05).

CONCLUSIONThree-stage sequential method could remarkably inhibit IL-5 mRNA expression in the lung tissue of asthmatic rats undergoing steroid treatment.