Signal pathways involved in emodin-induced contraction of smooth muscle cells from rat colon.
OBJECTIVE
To investigate the effects induced by emodin on single smooth 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 was measured by computerized image micrometry. Intracellular Ca2+ ([Ca2+]i) signals were studied using the fluorescent Ca2+ indicator fluo-3 and confocal microscopy. PKCalpha distribution at rest state or after stimulation was measured with immunofluorescence confocal microscopy.


RESULTS
(1) Emodin dose-dependently caused colonic smooth muscle cells contraction; (2) emodin induced an increase in intracellular Ca2+ concentration; (3) the contractile responses induced by emodin were respectively inhibited by 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 PKCalpha from cytosolic area to the membrane.


CONCLUSIONS
Emodin has a direct contractile effect on colonic smooth muscle cell. This signal cascade induced by emodin is initiated by increased [Ca2+]i and PKCalpha translocation, which in turn lead to the activation of MLCK and the suppression of MLCP. Both of them contribute to the emodin-induced contraction.
Ma
Tao
T
Department of Surgery, General Hospital of Tianjin Medical University, Tianjin 300052, China. mataoemail@yahoo.com.cn
Qi
Qing-Hui
QH
Xu
Jian
J
Dong
Zuo-Liang
ZL
Yang
Wen-Xiu
WX
D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D003106:Colon / Q000033:anatomy & histology / Q000187:drug effects; D004642:Emodin / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051571:Protein Kinase C-alpha; D051381:Rats; D017208:Rats, Wistar
D001381:Azepines; D004791:Enzyme Inhibitors; D009281:Naphthalenes; C061465:calphostin complex; C070571:ML 7; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D004642:Emodin; D002118:Calcium