Abstract: Objective To investigate the relaxant effect of rhein on mouse airway smooth muscle and the underlying mechanism. Methods SPF BALB/c male mice were sacrificed to isolate the tracheal rings（TRs）. After balancing in the perfusion system，the contraction tension of the TRs was recorded with JH-2 tension recording system. The TRs were precontracted using 80 mmol/L K⁺ . When the muscle tension of the TRs reached a steady state， the rhein was accumulatively added at concentrations of 1. 00，3. 16，10. 00，31. 60，100. 00，177. 80，200. 00 μmol/L，respectively，and the tension changes were observed. The control experiments were also performed. The effects of rhein on the currents of the L-type voltage-dependent Ca²⁺ channels（LVDCC）were recorded using patchclamp technique. Similarly，the effects of rhein at different concentrations on the levels of intracellular Ca²⁺（［Ca²⁺］_i）in airway smooth muscle cells were recorded using TILL calcium imaging system. Results The relaxant effects induced by rhein of 177. 80 μmol/L reached the maximal value（92. 7±8. 0）%. Rhein inhibited LVDCC-mediated currents and LVDCC-mediated increases of［Ca²⁺］_i，as well as contraction caused by calcium influx. Conclusion Rhein inhibits contraction of airway smooth muscle via inhibiting LVDCC.

Key words: airway smooth muscle, intracellular Ca²⁺ , L- type voltage- dependent Ca²⁺ channels（LVDCC）, rhein, asthma