Abstract:
Bile acids regulate gastrointestinal motility by mechanisms that are poorly understood. Standard isolated tissue bath assays might not recapitulate in vivo physiology if contractile responses to certain bile acids require direct application to the intestinal mucosa. We sought to determine the feasibility of quantifying longitudinal smooth muscle contractile responses to bile acids from intact segments of everted mouse ileum. Ileum from adult female C57BL/6J mice was isolated, gently everted over a notched metal rod, and mounted in tissue baths. Individual bile acids and agonists of bile acid receptors were added to the baths, and longitudinal smooth muscle contractile responses were quantified by isometric force transduction. Ursodeoxycholic acid robustly increased contractile responses in a dose-dependent manner. Deoxycholic acid stimulated contractility at low doses but inhibited contractility at high doses. Chenodeoxycholic acid, glycocholic acid, and lithocholic acid did not alter contractility. The dose-dependent increase in contractility resulting from the application of ursodeoxycholic acid was recapitulated by INT-777, an agonist of the Takeda G protein-coupled receptor 5 (TGR5), and by cevimeline, a muscarinic acetylcholine receptor agonist. Agonists to the nuclear receptors farnesoid X receptor, glucocorticoid receptor, pregnane X receptor, vitamin D receptor, and to the plasma membrane epidermal growth factor receptor did not modify baseline contractile patterns. These results demonstrate that gentle eversion of intact mouse ileum facilitates the quantification of longitudinal smooth muscle contractile responses to individual bile acids. Prokinetic effects of ursodeoxycholic acid and low-dose deoxycholic acid are replicated by agonists to TGR5 and muscarinic acetylcholine receptors.
摘要:
胆汁酸通过鲜为人知的机制调节胃肠运动。如果对某些胆汁酸的收缩反应需要直接应用于肠粘膜,则标准的分离组织浴测定法可能无法概括体内生理学。我们试图确定量化外翻小鼠回肠完整节段对胆汁酸的纵向平滑肌收缩反应的可行性。分离成年雌性C57BL/6J小鼠的回肠,轻轻翻过有缺口的金属棒,并安装在组织浴中。将单个胆汁酸和胆汁酸受体激动剂添加到浴中,纵向平滑肌收缩反应通过等距力转导进行量化。熊去氧胆酸以剂量依赖性方式强烈增加收缩反应。脱氧胆酸在低剂量时刺激收缩力,但在高剂量时抑制收缩力。鹅去氧胆酸,甘胆酸,石胆酸并没有改变收缩性。TakedaG蛋白偶联受体5(TGR5)的激动剂INT-777概括了由于应用熊去氧胆酸而导致的收缩力的剂量依赖性增加,通过西维美林,毒蕈碱乙酰胆碱受体激动剂。核受体法尼醇X受体的激动剂,糖皮质激素受体,孕烷X受体,维生素D受体,和质膜表皮生长因子受体没有改变基线收缩模式。这些结果表明,完整的小鼠回肠的温和外翻有助于量化对单个胆汁酸的纵向平滑肌收缩反应。熊去氧胆酸和低剂量脱氧胆酸的促动力作用被TGR5和毒蕈碱乙酰胆碱受体激动剂复制。