Relaxation effect of isoliensinine on isolated mouse airway smooth muscle

AIM: To study the relaxation effect of isoliensinine on high K⁺-induced isolated mouse airway smooth muscle (ASM) and the underlying mechanism. METHODS: The muscle tension transducer was used to detect the effects of isoliensinine on high K⁺-induced precontraction and Ca²⁺ influx in ASM. The technique of patch-clamp and calcium imaging system were respectively used to examine the effects of isoliensinine on LVDCC currents andCa²⁺]_i of the ASM cells (ASMCs). RESULTS: Isoliensinine significantly relaxed precontracted ASM induced by high K⁺ in a concentration-dependent manner. The maximum relaxation ratio was(95.3±3.9)% by isoliensinine at 100 μmol/L. In addition, LVDCC currents were measured using the whole-cell patch-clamp technique, which were abolished by isoliensinine. High K⁺-induced 340/380 nm fluorescence ratio of Fura-2 was 0.63±0.10 in ASMCs, while it decreased to 0.36±0.05 after the addition of isoliensinine (P<0.01). When isoliensinine was added at the peak point ofCa²⁺]_i, the ratio rapidly decreased from 0.74±0.02 to 0.42±0.05 (P<0.01). Moreover, isoliensinine inhibited high K⁺-induced Ca²⁺ influx-mediated contraction of ASM. CONCLUSION: Isoliensinine inhibits LVDCC currents, terminates Ca²⁺ influx and reducesCa²⁺]_i, eventually resulting in relaxation of the ASM, indicating isoliensinine might be a potential bronchodilator.