内脏高敏感大鼠结肠5-羟色胺转运体蛋白的表达

Serotonin transporter expression in rats with chronic visceral hypersensitivity

目的:探讨5-羟色胺转运体蛋白(SERT)在内脏高敏感性中的作用,为功能性胃肠病的发病机制研究提供理论基础.方法:采用乳鼠醋酸灌肠建立大鼠慢性内脏高敏感动物模型,同时设立对照组.待乳鼠成年后应用直肠内球囊扩张评估腹壁撤离反射(AWR)的方法,评估其内脏敏感性;检测髓过氧化物酶(MPO)评价其肠道黏膜炎症程度;用RT-PCR方法评价大鼠结肠SERT的mRNA水平,免疫组织化学方法评价大鼠结肠SERT的表达;用ELISA方法检测血浆和结肠组织5-HT水平.结果:乳鼠醋酸灌肠建立的大鼠慢性内脏高敏感模型组与对照组相比HE染色显示结肠黏膜未见明显急、慢性炎症改变;两组大鼠结肠组织MPO水平没有显著性差异;在不同容量下的AWR评分慢性内脏高敏感模型组显著高于对照组(P<0.01).血浆5-HT水平慢性内脏高敏感模型组明显高于对照组(95.75±15.99vs72.17±8.01,P<0.01),而两组结肠组织5-HT含量没有明显差异.免疫组织化学研究显示内脏高敏感模型组结肠上皮SERT表达水平显著低于对照组(0.187±0.010vs0.191±0.011P<0.01),而其结肠SERTmRNA水平显著高于对照组(16.02±3.7vs10.05±2.12,P<0.01).结论:内脏高敏感大鼠外周5-HT水平的增高主要来源于其灭活的减少而非合成的增加,与SERT的关系密切,结肠SERT可能具有不同的亚型和功能.

AIM：To determine whether colonic serotonin transporter（SERT） expression is altered in rats with visceral hypersensitivity and to explore the possible mechanism underlying the pathogenesis of visceral hypersensitivity.METHODS：A rat model of visceral hypersensitivity was created by intracolonic injection of acetic acid between postnatal days 8 and 21.The expression of SERT mRNA and protein in the colonic epithelium was detected by RT-PCR and immunohistochemistry,respectively.The levels of serotonin in plasma and colonic tissue were also measured.RESULTS：Colon irritation in neonates resulted in chronic visceral hypersensitivity in the absence of identifiable peripheral pathology.Under different capacities the abdominal withdrawal reflex（AWR） score in rats with chronic visceral hypersensitivity was significantly higher than that in controls（P 0.01）.Although plasma serotonin content significantly increased in rats with visceral hypersensitivity compared to controls（95.75 ± 15.99 vs 72.17 ± 8.01,P 0.01）,no significant difference was noted in colonic serotonin content between the two groups.SERT immunoreactivity in colonic epithelium was significantly reduced in rats with visceral hypersensitivity（0.187 ± 0.010 vs 0.191 ± 0.011,P 0.01）,whereas a significant increase was noted in SERT mRNA level in the colon of rats with visceral hypersensitivity compared to controls（16.02 ± 3.7 vs 9.47 ± 2.34,P 0.05）.CONCLUSION：In visceral hypersensitivity,the increase in serotonin content is mainly due to decreased degradation of the protein.The expression and function of SERT may be different in serotonergic neurons compared to colonic epithelial mucosa cells.