Quantitation of the Contractile Response Mediated by Two Receptors: M2 and M3 Muscarinic Receptor-Mediated Contractions of Human Gastroesophageal Smooth Muscle
Quantitation of the Contractile Response Mediated by Two Receptors: M2 and M3 Muscarinic Receptor-Mediated Contractions of Human Gastroesophageal Smooth Muscle
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DOI：
10.1124/jpet.108.148106
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发表时间：
2009-04-01
影响因子：
3.5
通讯作者：
Ruggieri, Michael R., Sr.
中科院分区：
文献类型：
--
作者：
Braverman, Alan S.;Miller, Larry S.;Ruggieri, Michael R., Sr.
尽管已知毒蕈碱受体可介导人胃肠道平滑肌的强直收缩，但介导强直收缩的受体亚型尚不完全清楚。附有食道的整个人胃是从器官移植捐献者那里获得的。测定了卡扣、吊带、下食管环肌 (LEC)、中食管环肌 (MEC) 和中食管纵向肌条 (MEL) 的胆碱能收缩反应。吊带纤维比其他纤维收缩得更大。通过免疫沉淀法测定这些解剖中的每一个的总、M-2和M-3毒蕈碱受体密度。 M-2 受体密度在吊带纤维中最大，其次是扣环、LEC、MEC，然后是 MEL，而 M-3 受体密度在 LEC 中最大，其次是 MEL、MEC、吊带，然后是扣环。通过Schild分析计算亚型选择性拮抗剂抑制氨甲酰甲胆碱诱导的收缩的效力以确定哪些毒蕈碱受体亚型有助于收缩。结果表明 M-2 和 M-3 受体介导扣环和吊带纤维的收缩。因此，这种多个受体介导收缩反应的分析是不合适的，因此提出了将M-2和M-3受体的双重占据与收缩相关的分析方法。使用这种新的分析方法，发现 M-2 毒蕈碱受体在介导扣环和吊带纤维收缩方面比在 LEC、MEC 和 MEL 肌肉中发挥更大的作用，其中 M-3 受体主要介导收缩。
Although muscarinic receptors are known to mediate tonic contraction of human gastrointestinal tract smooth muscle, the receptor subtypes that mediate the tonic contractions are not entirely clear. Whole human stomachs with attached esophagus were procured from organ transplant donors. Cholinergic contractile responses of clasp, sling, lower esophageal circular (LEC), midesophageal circular (MEC), and midesophageal longitudinal (MEL) muscle strips were determined. Sling fibers contracted greater than the other fibers. Total, M-2 and M-3 muscarinic receptor density was determined for each of these dissections by immunoprecipitation. M-2 receptor density is greatest in the sling fibers, followed by clasp, LEC, MEC, and then MEL, whereas M-3 density is greatest in LEC, followed by MEL, MEC, sling, and then clasp. The potency of subtypeselective antagonists to inhibit bethanechol- induced contraction was calculated by Schild analysis to determine which muscarinic receptor subtypes contribute to contraction. The results suggest both M-2 and M-3 receptors mediate contraction in clasp and sling fibers. Thus, this type of analysis in which multiple receptors mediate the contractile response is inappropriate, and an analysis method relating dual occupation of M-2 and M-3 receptors to contraction is presented. Using this new method of analysis, it was found that the M-2 muscarinic receptor plays a greater role in mediating contraction of clasp and sling fibers than in LEC, MEC, and MEL muscles in which the M-3 receptor predominantly mediates contraction.