Department of Pharmacology, Dalian Medical University, Dalian, China.
Can J Physiol Pharmacol. 2012 Apr;90(4):455-62. doi: 10.1139/y2012-004. Epub 2012 Mar 27.
Emodin is traditionally used as a laxative and is found to increase or decrease the contractility of intestinal smooth muscle in low doses and high doses, respectively. In this study, we propose that bidirectional regulation (BR) on the contractility of jejunal smooth muscle (CJSM) is inducible by emodin in the absence of control by the central nervous system. The results indicated that emodin-induced BR had the following characteristics. A stimulatory effect on CJSM was induced by emodin at 7 low contractile states, and an inhibitory effect was induced on CJSM at 7 high contractile states. Emodin-induced BR on myosin phosphorylation was also observed. BR was not observed in the presence of tetrodotoxin, suggesting that enteric nervous system is required for producing BR. The stimulatory effect of emodin on CJSM was abolished by atropine and diphenhydramine, respectively, suggesting that BR was correlated with cholinergic and histamine system while jejunal smooth muscle was at low contractile state. The inhibitory effect of emodin on CJSM was abolished by phentolamine, propranolol, and L-NG-nitroarginine (L-NNA), respectively, suggesting that BR was related to adrenergic hyperactivity and with a nitric oxide relaxing mechanism while jejunal smooth muscle was in a high contractile state. The exact mechanism, however, needs further investigation.
大黄素传统上被用作泻药，在低剂量和高剂量下分别被发现增加或降低肠道平滑肌的收缩性。在这项研究中，我们提出大黄素在没有中枢神经系统控制的情况下对空肠平滑肌（CJSM）的收缩性具有双向调节（BR）作用。结果表明，大黄素诱导的 BR 具有以下特征。在 7 种低收缩状态下，大黄素对 CJSM 产生兴奋作用，在 7 种高收缩状态下，大黄素对 CJSM 产生抑制作用。还观察到大黄素诱导的肌球蛋白磷酸化的 BR。在存在河豚毒素的情况下未观察到 BR，表明产生 BR 需要肠神经系统。大黄素对 CJSM 的刺激作用分别被阿托品和苯海拉明所阻断，表明 BR 与胆碱能和组胺系统相关，而空肠平滑肌处于低收缩状态。大黄素对 CJSM 的抑制作用分别被酚妥拉明、心得安和 L-NG-硝基精氨酸（L-NNA）所阻断，表明 BR 与肾上腺素能活性亢进有关，且具有一氧化氮松弛机制，而空肠平滑肌处于高收缩状态。然而，确切的机制仍需要进一步研究。
