Mao Y K, Wang Y F, Daniel E E
Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
Peptides. 1996;17(5):839-43. doi: 10.1016/0196-9781(96)00084-8.
The binding of [3H]substance P (SP) was localized and characterized in canine small intestine. The highest density of [3H]SP binding occurred in the fraction enriched in circular muscle membranes (Bmax 148 +/- 14 fmol/mg; Kd 0.81 +/- 0.01 nM). In the kinetics studies binding was reversible, yielding a similar Kd value. NK1 agonists and antagonists fully displaced, but ligands at the NK2 and NK3 receptor only partially displaced, [3H]SP binding. The potency order of displacement resembled that for the human NK1 receptor ortholog rather than the rat NK1 receptor. Densities of [3H]SP binding were lower in myenteric plexus and longitudinal muscle membrane fractions, but suggested binding in both neural and muscle membranes. The conclusion is that NK1 receptors occur primarily in canine intestine circular muscle plasma membrane.
[3H]P物质（SP）的结合在犬小肠中进行了定位和特性研究。[3H]SP结合的最高密度出现在富含环行肌膜的部分（最大结合容量Bmax为148±14 fmol/mg；解离常数Kd为0.81±0.01 nM）。在动力学研究中，结合是可逆的，产生相似的Kd值。NK1激动剂和拮抗剂可完全取代[3H]SP结合，但NK2和NK3受体的配体只能部分取代[3H]SP结合。取代的效价顺序类似于人类NK1受体直系同源物而非大鼠NK1受体。[3H]SP结合密度在肌间神经丛和纵行肌膜部分较低，但提示在神经膜和肌膜中均有结合。结论是NK1受体主要存在于犬小肠环行肌质膜中。
