摘要
AIM: To investigate whether emodin has any effects on circular smooth muscle cells of rat colon and to examine the mechanism underlying its effect.METHODS: Smooth muscle cells were isolated from the circular muscle layer of Wistar rat colon and the cell length was measured by computerized image micrometry.Intracellular Ca2+([Ca2+]i) signalling was studied in smooth muscle cells using Ca2+ indicator Fluo-3 AM on a laserscanning confocal microscope.RESULTS: Emodin dose-dependently induced smooth muscle cells contraction. The contractile responses induced by emodin were inhibited by preincubation of the cells with ML-7 (an inhibitor of MLCK). Emodin caused a large, transient increase in [Ca2+]i followed by a sustained elevation in [Ca2+]i.The emodin -induced increase in [Ca2+]i was unaffected by nifedipine, a voltage-gated Ca2+-channel antagonist, and the sustained phase of the rising of [Ca2+]i was attenuated by extracellular Ca2+ removal with EGTA solution. Inhibiting Ca2+release from ryanodine-sensitive intracellular stores by ryanodine reduced the peak increasein [ca2+]i.Using heparin, an antagonist of IP3R, almost abolished the peak increase in [Ca2+]i.CONCLUSION: Emodin has a direct excitatory effect on circular smooth muscle cells in rat colon mediated via Ca2+/CaM dependent pathways. Furthermore, emodin-induced peak [Ca2+]i increase may be attributable to the Ca2+release from IP3 sensitive stores, which further promote Ca2+ release from ryanodine-sensitive stores through CICR mechanism.Additionally, Ca2+ influx from extracellular medium contributes to the sustained increase in[Ca2+]i.
AIM: To investigate whether emodin has any effects on circular smooth muscle cells of rat colon and to examine the mechanism underlying its effect.METHODS: Smooth muscle cells were isolated from the circular muscle layer of Wistar rat colon and the cell length was measured by computerized image micrometry. Intracellular Ca<sup>2+</sup> ([Ca<sup>2+</sup>]i) signalling was studied in smooth muscle cells using Ca<sup>2+</sup> indicator Fluo-3 AM on a laser-scanning confocal microscope.RESULTS: Emodin dose-dependently induced smooth muscle cells contraction. The contractile responses induced by emodin were inhibited by preincubation of the cells with ML-7 (an inhibitor of MLCK). Emodin caused a large, transient increase in [Ca<sup>2+</sup>]i followed by a sustained elevation in [Ca<sup>2+</sup>]i. The emodin -induced increase in [Ca<sup>2+</sup>]i was unaffected by nifedipine, a voltage-gated Ca<sup>2+</sup>-channel antagonist, and the sustained phase of the rising of [Ca<sup>2+</sup>]i was attenuated by extracellular Ca<sup>2+</sup> removal with EGTA solution. Inhibiting Ca<sup>2+</sup> release from ryanodine-sensitive intracellular stores by ryanodine reduced the peak increase in [Ca<sup>2+</sup>]i. Using heparin, an antagonist of IP<sub>3</sub>R, almost abolished the peak increase in [Ca<sup>2+</sup>]i.CONCLUSION: Emodin has a direct excitatory effect on circular smooth muscle cells in rat colon mediated via Ca<sup>2+</sup>/ CaM dependent pathways. Furthermore, emodin-induced peak [Ca<sup>2+</sup>]i increase may be attributable to the Ca<sup>2+</sup> release from IP<sub>3</sub> sensitive stores, which further promote Ca<sup>2+</sup> release from ryanodine-sensitive stores through CICR mechanism. Additionally, Ca<sup>2+</sup> influx from extracellular medium contributes to the sustained increase in [Ca<sup>2+</sup>]i.
基金
the National Natural Science Foundation of China,No.30171198
