Ito Yoshihiko, Oyunzul Luvsandorj, Seki Masanao, Fujino Oki Tomomi, Matsui Minoru, Yamada Shizuo
Department of Pharmacokinetics and Pharmacodynamics and Global Center of Excellence Program, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka, Japan.
Br J Pharmacol. 2009 Apr;156(7):1147-53. doi: 10.1111/j.1476-5381.2009.00113.x.
To compare loss in binding to muscarinic receptor (mAChR) subtypes with their known functions, the total density of muscarinic receptors was measured in peripheral tissues from wild type (WT) and mAChR knockout (KO) mice.
Binding parameters of [N-methyl-3H]scopolamine methyl chloride ([3H]NMS) were determined in 10 peripheral tissues of WT and M1-M5 receptor KO mice. Competition between [3H]NMS and darifenacin (selective M3 receptor antagonist) was also measured.
There was an extensive loss of [3H]NMS-binding sites (maximal number of binding sites, Bmax) in heart and smooth muscle from M2KO mice, compared with WT mice. Smooth muscle from M3KO mice also showed a moderate loss of Bmax. Bmax fell in pancreas and bladder of M4KO mice and in prostate in M1KO and M3KO mice. There was a large loss of Bmax in exocrine and endocrine glands of M3KO mice with a moderate decrease in M2KO mice. Darifenacin inhibited specific [3H]NMS binding in submandibular gland and bladder of WT, M2KO and M3KO mice. Ki (inhibition constant) values for darifenacin in the submandibular gland were the same in WT and M2KO mice but increased in M3KO mice. However, Ki values in bladder were decreased in M2KO mice and increased in M3KO mice.
Single mAChR KO mice exhibit a loss of mAChR in peripheral tissues that generally paralleled the reported loss of function. Quantitative analysis of data, however, also suggested that, in some instances, normal expression of a receptor subtype depended on expression of other subtypes.
为了比较与已知功能的毒蕈碱受体（mAChR）亚型结合的丧失情况，在野生型（WT）和mAChR基因敲除（KO）小鼠的外周组织中测量了毒蕈碱受体的总密度。
测定了WT和M1 - M5受体KO小鼠10种外周组织中[甲基 - 3H]东莨菪碱甲基氯（[3H]NMS）的结合参数。还测量了[3H]NMS与达非那新（选择性M3受体拮抗剂）之间的竞争情况。
与WT小鼠相比，M2KO小鼠心脏和平滑肌中[3H]NMS结合位点（最大结合位点数，Bmax）大量丧失。M3KO小鼠的平滑肌也显示出Bmax适度丧失。M4KO小鼠胰腺和膀胱以及M1KO和M3KO小鼠前列腺中的Bmax下降。M3KO小鼠的外分泌腺和内分泌腺中Bmax大量丧失，M2KO小鼠中适度下降。达非那新抑制WT、M2KO和M3KO小鼠下颌下腺和膀胱中特异性[3H]NMS结合。WT和M2KO小鼠下颌下腺中达非那新的Ki（抑制常数）值相同，但M3KO小鼠中升高。然而，M2KO小鼠膀胱中的Ki值降低，M3KO小鼠中升高。
单一mAChR基因敲除小鼠外周组织中mAChR丧失，这通常与报道的功能丧失情况平行。然而，数据的定量分析还表明，在某些情况下，一种受体亚型的正常表达取决于其他亚型的表达。
