便秘型肠易激综合征新概念模型的建立

A new model of constipation-predominant irritable bowel syndrome in rats

目的:以肠易激综合征(IBS)模型新概念建立一种便秘型IBS 大鼠模型,为IBS的研究提供新的条件. 方法:出生后4 wk Wistar大鼠,随机分为冰水灌胃组、常温水灌胃细及正常对照组.前两组每日分别给予冰水及常温水灌胃14 d,观察灌胃期间三组大鼠灌胃后3 h内和3- 24 h间的大便粒数及含水量变化,停止灌胃后继续观察14 d对应时间段的大便粒数及含水量变化以评价其便秘.28 d 观察结束后给予直肠内球囊扩张,测定引起腹部收缩反射的最小容量阈值及直肠内球囊不同容量扩张时腹部收缩反射的次数,评价其肠道对扩张刺激的敏感性.各组动物回盲部及结肠肥大细胞(MC)研究应用甲苯胺蓝染色、计数. 5-羟色胺(5-HT)在肠道的表达应用免疫组织化学染色及彩色病理图像分析系统进行半定量分析. 结果:冰水灌胃组大鼠灌胃后3h内大便粒数及含水量较常温水灌胃组和正常对照组明显增加(P<0.05);停止灌胃后三组大鼠对应时间段3h内大便粒数及含水量无明显差异(P>0.05). 冰水灌胃组前14 d灌胃后3-24 h间的大便粒数及含水量均较常温水灌胃组和正常对照组明显减少(P<0.05);停止灌胃后,此趋势继续保持至第28 d实验结束.直肠内球囊扩张时,冰水灌胃组引起腹部收缩的最小容量阈值略高于正常对照组,但统计学比较无明显差异(P>0.05).直肠球囊体积1.0 mL低容量扩张时冰水灌胃组3 min内腹部收缩反射次数明显低于正常对照组(P<0.05);球囊体积1.5 mL, 2.0 mL高容量扩张时两组无明显差异(P>0.05).冰水灌胃组回盲部和结肠MC计数均明显高于正常对照组(P<0.05).冰水灌胃组回盲部、结肠黏膜层5-HT阳性细胞的面积均明显高于正常对照组(P<0.05). 结论:采用冰水灌胃法建立了大鼠便秘模型,该模型具有肠道敏感性降低、回盲部及结肠MC增多、5-HT阳性内分泌细胞增多,较好地模拟了人的C-IBS特征,显示了IBS 动物模型的新概念.

AIM: To set up a new model of constipation-predominant irritable bowel syndrome (C-IBS) in rats and to study the possible pathogenesis of IBS. METHODS: Wistar rats of postnatal four weeks were divided into three groups: group A (stomach irritation with 0-4 ℃ cool water), group B (stomach irritation with room temperature water) and group C (control group). Both of rats in groups A and B received stomach irritation daily for fourteen days. In these fourteen days, the feces of rats in three groups were collected and the feces granules were counted, moisture contents of the feces were calculated daily during 0 to 3 hours and 3 to 24 hours, respectively. After suspending the irritation of cool water, the granules and moisture contents of feces in corresponding periods were observed for the following fourteen days continuously in order to evaluate the degree of constipation. Then perception thresholds and the number of abdominal withdrawal reflexes (AWR) were recorded during rectal balloon distention in order to evaluate bowel sensitivity. The ileocecal junction and colon samples were stained by haematoxylin-eosin (HE) for routine pathologic examination and the improved toluidine blue method for mast cells, respectively. The expression of 5-hydroxymetryptamine (5-HT) on bowel was showed by immunohistochemical staining, and analyzed semi-quantitatively by computer color image analyzer. RESULTS: The granules and moisture contents of feces during 0 to 3 hours after cool water irritation were significantly higher in group A than in groups B and C (P<0.05), but the differences disappeared after suspending irritation (P>0.05). The granules and moisture contents of feces during 3 to 24 hours after cool water irritation were significantly lower in group A than in groups B and C (P <0.05). After suspending stomach irritation with cool water, the tendency lasted at least for fourteen days. The perception threshold of group A was slightly higher than that of group C during rectal balloon distention, but there was no significant difference (P >0.05). The number of AWR to the lower balloon content (1.0 mL) was much lower in group A than in group C (P<0.05), but the AWR to the balloon distention at 1.5ml and 2.0ml were similar between these two groups. In group A, the number of mast cells (MCs) in the ileocecal junction and colon were significantly higher than those of group C (P<0.05), and the areas of 5-HT positive cells were markedly higher than those of group C (P<0.05). CONCLUSION: The model of C-IBS induced by stomach irritation with cool water is stable for constipation and characterized by decreased bowel sensitivity, increased MCs and 5-HT immunoreactive positive cells, which satisfactorily imitates the bowel features of C-IBS patients and shows a new concept model for IBS.