Grider J R, Bitar K N, Makhlouf G M
Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0711.
Gastroenterology. 1987 Nov;93(5):951-7. doi: 10.1016/0016-5085(87)90556-7.
Muscle cells were isolated from the longitudinal muscle layer of guinea pig and human jejunum and used to identify the muscarinic receptor subtype (M1 or M2) that mediates contraction. Single muscle cells were anchored to the ceiling of a minichamber and their contraction was measured in response to acetylcholine, alone and in combination with three muscarinic antagonists: atropine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), and pirenzepine. Estimates of the inhibitory dissociation constants (Ki) were closely similar in human and guinea pig muscle cells (atropine 2.5-5 X 10(-11) M, 4-DAMP 1.9-2.9 X 10(10) M, and pirenzepine 8.2-9.5 X 10(-8) M). Thus, pirenzepine, a preferential M1 antagonist, was 1900-3280 times less potent than atropine and 279-500 times less potent than 4-DAMP. Comparative measurements on longitudinal muscle strips from guinea pig jejunum confirmed the greater potency of atropine and 4-DAMP relative to pirenzepine. Inactivation of muscarinic receptors on single muscle cells with dibenamine showed that only a small fraction of receptors was responsible for the response to acetylcholine. It was concluded that intestinal muscle cells contain a large reservoir of muscarinic M2 receptors that exhibit considerable spareness and heterogeneity.
从豚鼠和人类空肠的纵肌层分离出肌肉细胞，用于鉴定介导收缩的毒蕈碱受体亚型（M1或M2）。将单个肌肉细胞固定在小室的顶部，并测量它们对乙酰胆碱单独作用以及与三种毒蕈碱拮抗剂（阿托品、4-二苯基乙酰氧基-N-甲基哌啶甲碘化物（4-DAMP）和哌仑西平）联合作用时的收缩情况。在人类和豚鼠肌肉细胞中，抑制解离常数（Ki）的估计值非常相似（阿托品为2.5 - 5×10⁻¹¹ M，4-DAMP为1.9 - 2.9×10⁻¹⁰ M，哌仑西平为8.2 - 9.5×10⁻⁸ M）。因此，作为选择性M1拮抗剂的哌仑西平的效力比阿托品低1900 - 3280倍，比4-DAMP低279 - 500倍。对豚鼠空肠纵肌条的比较测量证实了阿托品和4-DAMP相对于哌仑西平具有更高的效力。用双苄胺使单个肌肉细胞上的毒蕈碱受体失活表明，只有一小部分受体对乙酰胆碱的反应起作用。得出的结论是，肠道肌肉细胞含有大量毒蕈碱M2受体储备，这些受体表现出相当大的备用性和异质性。
