Sim M K, Manjeet S
Department of Pharmacology, Faculty of Medicine, National University of Singapore.
Eur J Pharmacol. 1990 Dec 15;189(6):399-404. doi: 10.1016/0922-4106(90)90037-x.
The second messenger response of cultured smooth muscle and endothelial cells of the rabbit aorta to acetylcholine (ACh) was investigated. ACh induced a concentration-dependent accumulation of inositol-monophosphate (InsP1) in the smooth muscle cells and a concentration-dependent reduction in basal production of adenosine 3',5'-cyclic monophosphate (cAMP) in the endothelial cells. Atropine, scopolamine and nitric oxide (NO) inhibited the ACh-induced accumulation of InsP1. The IC50 values were 55 +/- 4.3 nM, 81.2 +/- 6.5 microM and 13.3 +/- 3.5 microM, respectively. On the other hand, the inhibition of reduction in basal production of cAMP was inhibited by scopolamine (IC50 = 55.3 +/- 4.3 nM) and atropine (IC50 = 63.2 +/- 5.2 microM). Pirenzepine inhibited both the ACh-induced accumulation of InsP1 (IC50 = 1.5 +/- 0.01 microM) and reduction of basal production of cAMP (IC50 = 812 +/- 33.5 nM). However, unlike scopolamine or atropine, the M1-selective ligand was not selective to either the endothelial or smooth muscle receptors. These results demonstrate for the first time the second messenger response of the action of ACh on the endothelial muscarinic receptors and the inhibition of InsP1 formation by NO. In addition, the results also support our earlier findings that the muscarinic receptors in the endothelium and smooth muscle of the rabbit aorta can be differentiated by atropine and scopolamine, namely, the endothelial receptors have high affinity for scopolamine but extremely low affinity for atropine whilst the reverse holds true for the smooth muscle receptors.
研究了兔主动脉培养的平滑肌细胞和内皮细胞对乙酰胆碱（ACh）的第二信使反应。ACh诱导平滑肌细胞中肌醇单磷酸（InsP1）呈浓度依赖性积累，诱导内皮细胞中腺苷3',5'-环磷酸（cAMP）基础生成量呈浓度依赖性降低。阿托品、东莨菪碱和一氧化氮（NO）抑制ACh诱导的InsP1积累。IC50值分别为55±4.3 nM、81.2±6.5 μM和13.3±3.5 μM。另一方面，东莨菪碱（IC50 = 55.3±4.3 nM）和阿托品（IC50 = 63.2±5.2 μM）抑制cAMP基础生成量降低。哌仑西平抑制ACh诱导的InsP1积累（IC50 = 1.5±0.01 μM）和cAMP基础生成量降低（IC50 = 812±33.5 nM）。然而，与东莨菪碱或阿托品不同，M1选择性配体对内皮或平滑肌受体均无选择性。这些结果首次证明了ACh作用于内皮毒蕈碱受体的第二信使反应以及NO对InsP1形成的抑制作用。此外，这些结果也支持了我们早期的发现，即兔主动脉内皮和平滑肌中的毒蕈碱受体可通过阿托品和东莨菪碱进行区分，即内皮受体对东莨菪碱具有高亲和力但对阿托品具有极低亲和力，而平滑肌受体则相反。
