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AIM: To investigate the effects induced by emodin on singlesmooth muscle cells from rat colon in vitro,and to determinethe signal pathways involved.METHODS: Cells were isolated from the muscle layers ofWistar rat colon by enzymatic digestion.Cell length wasmeasured by computerized image micrometry.IntracellularCa~(2+) ([Ca~(2+)]i) signals were studied using the fluorescent Ca~(2+)indicator fluo-3 and confocal microscopy.PKCα distributionat rest state or after stimulation was measured withimmunofluorescence confocal microscopy.RESULTS: (1) Emodin dose-dependently caused colonicsmooth muscle cells contraction; (2) emodin induced anincrease in intracellular Ca~(2+) concentration; (3) the contractileresponses induced by emodin were respectively inhibitedby preincubation of the cells with ML-7 (an inhibitor of MLCK)and calphostin C (an inhibitor of PKC); (4) Incubation ofcells with emodin caused translocation of PKCα from oltosolicarea to the membrane.CONCLUSION: Emodin has a direct contractile effect oncolonic smooth muscle cell.This signal cascade induced byemodin is initiated by increased [Ca~(2+)]i and PKα translocation,which in turn lead to the activation of MLCK and thesuppression of MLCP.Both of them contribute to the emodin-induced contraction.
To investigate the effects induced by emodin on singlesmooth muscle cells from rat colon in vitro, and to determine the signal pathways involved. METHODS: Cells were isolated from the muscle layers of Wistar rat colon by enzymatic digestion. Cell length wasmeasured by computerized image micrometry. Intracellular Ca 2+ ([Ca 2+] i) signals were studied using the fluorescent Ca 2+ indicator fluo-3 and confocal microscopy. PKCα distributionat rest state or after stimulation was measured with immunofluorescence confocal microscopy. RESULTS: (1) Emodin dose-dependently caused colonicsmooth muscle cells contraction; (2) emodin induced anincrease in intracellular Ca ~ (2+) concentration; (3) the contractileresponses induced by emodin were suppressed respectively preincubation of the cells with ML- 7 (an inhibitor of MLCK) and calphostin C (an inhibitor of PKC); (4) Incubation of cells with emodin caused translocation of PKCa from oltosolicarea to the membrane. CONCLUSION: Emodin has a direct contr actile effect oncolonic smooth muscle cell. This signal cascade induced by emodin is initiated by increased [Ca ~ (2 +)] i and PKα translocation, which in turn lead to the activation of MLCK and the suppression of MLCP. Both of them contribute to the emodin -induced contraction