Wei H B, Roeske W R, Lai J, Wanibuchi F, Hidaka K, Usuda S, Yamamura H I
Department of Pharmacology, University of Arizona Health Science Center, Tucson 85724.
Life Sci. 1992;50(5):355-63. doi: 10.1016/0024-3205(92)90437-t.
To investigate the pharmacological effect of a novel compound YM796, we performed radioligand binding experiments and correlative biochemical experiments using the transfected murine fibroblast B82 cells which expressed the m1 and m2 muscarinic receptor genes (cloned cell lines designated as LK3-3 and M2LKB2-2, respectively). 3Hmethyl-3-quinuclidinyl benzilate ( 3HMQNB) binding in these transfected cell lines was inhibited by different optical isomers of YM796 and other muscarinic drugs, atropine, pirenzepine, AF-DX 116, as well as selected agonists. (-)YM796, (+)YM796 and (+/-)YM796 inhibited 3HMQNB binding in LK3-3 cells with Ki values of 16.4 microM, 30.1 microM and 21.8 microM and in M2LKB2-2 cells with Ki values of 52.0 microM, 108 microM and 77.1 microM, respectively. From functional assays we found the two isomers, (-)YM796 and (+)YM796 had different intrinsic activities for the M1 and M2 muscarinic receptors. (-)YM796 revealed agonistic activity: stimulation of [3H]IP1 accumulation in LK3-3 cells with an EC50 value of 26.5 microM, which was less efficacious (the Emax value was 5.6 times basal) than carbachol, a full agonist (the Emax value was 17.2 times basal). Interestingly, (-)YM796 did not show significant inhibition of cAMP formation in M2LKB2-2 cells except at extremely high concentrations (greater than 1mM). (+)YM796 exhibited no significant efficacy for the M1 and M2 muscarinic receptors. These results suggest that (-)YM796 represents a muscarinic partial agonist with functional selectivity for the M1 muscarinic receptors whereas (+)YM796 shows no efficacy for either M1 or M2 muscarinic receptors in these transfected cells.
为研究新型化合物YM796的药理作用，我们使用转染了毒蕈碱受体m1和m2基因的小鼠成纤维细胞B82细胞（分别命名为LK3 - 3和M2LKB2 - 2的克隆细胞系）进行了放射性配体结合实验和相关生化实验。在这些转染细胞系中，3H甲基-3-喹核醇基苯甲酸酯3HMQNB的结合受到YM796的不同光学异构体以及其他毒蕈碱药物、阿托品、哌仑西平、AF - DX 116和选定激动剂的抑制。(-)YM796、(+)YM796和(+/-)YM796抑制LK3 - 3细胞中3HMQNB结合的Ki值分别为16.4 microM、30.1 microM和21.8 microM，抑制M2LKB2 - 2细胞中3HMQNB结合的Ki值分别为52.0 microM、108 microM和77.1 microM。从功能实验中我们发现，两种异构体(-)YM796和(+)YM796对M1和M2毒蕈碱受体具有不同的内在活性。(-)YM796表现出激动活性：刺激LK3 - 3细胞中[3H]IP1积累，EC50值为26.5 microM，其效力低于完全激动剂卡巴胆碱（Emax值为基础值的17.2倍，而(-)YM796的Emax值为基础值的5.6倍）。有趣的是，(-)YM796在M2LKB2 - 2细胞中除了在极高浓度（大于1mM）时外，对cAMP形成没有显著抑制作用。(+)YM796对M1和M2毒蕈碱受体没有显著效力。这些结果表明，(-)YM796是一种对M1毒蕈碱受体具有功能选择性的毒蕈碱部分激动剂，而(+)YM796在这些转染细胞中对M1或M2毒蕈碱受体均无效力。
