忍冬藤提取物对兔离体肠平滑肌的舒张作用及其机制

【目的】胃肠平滑肌过度收缩可引起腹痛腹泻等临床常见的疾病。目前,临床上对治疗胃肠平滑肌过度收缩的药物主要以西药为主,如钙离子通道阻断药硝苯地平和抗胆碱药阿托品等,硝苯地平长期使用可引起负性肌力和负性传导的现象,而阿托品由于其不良反应较大,在临床应用中受到一定的限制。因此,开发具有有效防治胃肠平滑肌痉挛、低毒、低残留的天然中草药意义重大。试验以兔离体小肠平滑肌为研究对象,利用丰富的忍冬藤资源,研究忍冬藤提取物对兔离体小肠平滑肌收缩的影响,并探讨其作用机制。【方法】采用兔离体小肠平滑肌试验,应用BL-420E生物机能实验系统,观察忍冬藤提取物对正常状态下兔离体小肠平滑肌自发性收缩的影响;进而使用工具药乙酰胆碱、组胺和氯化钡致兔小肠痉挛性收缩后,观察忍冬藤提取物对其痉挛性收缩的影响;为研究忍冬藤提取物抑制兔离体小肠平滑肌收缩的作用机制,应用IP_3受体阻断剂肝素(HP)、肌浆网ryanodine受体阻断剂钌红(RR)和一氧化氮合酶抑制剂左旋硝基精氨酸甲酯(L-NAME),探明忍冬藤提取物对兔离体小肠平滑肌作用的机制。【结果】忍冬藤提取物可浓度依赖性抑制兔离体小肠平滑肌自发性收缩,药物浓度在7.5 g·L~(-1)时可显著抑制兔离体小肠平滑肌收缩的频率(P0.05),药物浓度在5g·L~(-1)时可极显著抑制兔离体小肠平滑肌收缩的振幅(P0.05);工具药乙酰胆碱、组胺和氯化钡可显著诱导兔小肠平滑肌收缩的振幅,忍冬藤提取物可显著抑制由乙酰胆碱、组胺和氯化钡诱导的兔离体小肠平滑肌收缩的频率(P0.05),可极显著抑制兔离体小肠平滑肌收缩的振幅(P0.01)。IP_3受体阻断剂肝素能增强忍冬藤提取物舒张兔离体小肠平滑肌收缩的作用(P0.01),而肌浆网ryanodine受体阻断剂钌红对忍冬藤提取物舒张兔小肠平滑肌的作用无明显影响(P0.05)。左旋硝基精氨酸甲酯能够部分阻断忍冬藤提取物舒张兔离体小肠平滑肌收缩的作用(P0.01)。【结论】忍冬藤提取物可显著抑制兔离体小肠平滑肌收缩的频率和振幅,其机制可能与增加一氧化氮浓度,抑制IP_3受体介导的内钙释放有关,但对肌浆网ryanodine受体途径引起的内钙释放无关。

Relaxed Effect of Caulis Lonicerae Extraction on Contraction of Intestinal Smooth Muscle of Rabbit in Vitro and Its Mechanism

【Objective】Excessive gastrointestinal smooth muscle contraction cause abdominal pain and diarrhea diseases in clinical. Recently, Ca²⁺ channel blocker nifedipine and anticholinergic atropine are widely employed in the treatment of gastrointestinal excessive contraction. However, nifedipine has a potent negative inotropic and dromotropic effects with dose increase after long-term administration, and atropine has severe side-effects which highly limited its clinical utilization. Therefore, it is important to develop natural medicines with high activity, low toxicity and no residue. In this research, the effects of Caulis lonicerae extraction on spontaneous smooth muscle contractions in isolated rabbit small intestine were investigated and the possible mechanism was explored.【Method】The in vitro intestine movement experiment, was conducted and the BL-420E biologic function analysis system was employed. The influences of C. lonicerae extraction on spontaneous contractions of the rabbit intestinal smooth muscle were measured. The effects of C. lonicerae extraction on spasmodic muscle contractions were measured by using acetylcholine (ACh), histamine (HA) and BaCl₂. The mechanism of C. lonicerae extraction was studied by using inositol 1,4,5-trisphosphate (IP₃) receptor antagonist (heparin, HP), ryanodine receptor antagonist (ruthenium red, RR) and a nitric oxide synthase (NOS) inhibitor (Nitro-L-arginine methyl ester, L-NAME).【Result】The results showed that the extraction of Caulis lonicerae extraction dose-dependently inhibited the spontaneous contraction of intestinal smooth muscle. Caulis lonicerae extraction, at the concentration of 7.5 g·L^-1, showed highly inhibition effects on the frequency of spontaneous contractions (P< 0.05). Meanwhile, at the concentration of 5 g·L^-1, significantly inhibition effects on the amplitude of spontaneous contractions (P < 0.05) were detected. ACh, HA and BaCl₂ significantly induced the amplitude of smooth muscle contractions, and C. lonicerae extraction notably inhibited the muscle contractions induced by ACh, HA and BaCl₂ (P < 0.05 or P < 0.01). IP₃ receptor antagonist heparin could strengthen the relaxed effects of C. lonicerae extraction on intestinal smooth muscle, but ryanodine receptor antagonist ruthenium red had no effect on the relaxation of C. lonicerae extraction. L-NAME inhibited the relaxation of C. lonicerae extraction (P < 0.01).【Conclusion】The extraction of C. lonicerae inhibited the frequency and amplitude of intestinal smooth muscle contractions of rabbits in vitro. The mechanism may be related to the increase of NO concentration in intestinal smooth muscle, and the inhibiting intracellular Ca²⁺ released via IP₃ of sarcoplasmic reticulum.