Widdop S, Daykin K, Hall I P
Department of Therapeutics, University Hospital of Nottingham, United Kingdom.
Am J Respir Cell Mol Biol. 1993 Nov;9(5):541-6. doi: 10.1165/ajrcmb/9.5.541.
[3H]-inositol phosphate formation and the inhibition of isoproterenol-induced [3H]-cyclic adenosine monophosphate (AMP) formation in response to the muscarinic agonist carbachol were studied in cultured human airway smooth muscle cells. Stimulation with carbachol produced concentration-dependent inhibition of isoproterenol (1 microM)-induced cyclic AMP formation (EC50, 0.15 microM; maximal inhibition, 60%). This response was itself reversed by pertussis toxin (100 ng/ml) and was competitively inhibited by the muscarinic antagonists pirenzepine (pA2, 6.5), methoctramine (pA2, 8.0), 4-diphenylacetoxy-N-methyl-piperidine (pA2, 8.0), and parafluorohexahydrosiladifenidol (pA2, 6.5), indicating that the M2 receptor subtype was mediating this response. In addition, carbachol also induced [3H]-inositol phosphate formation in these cells (EC50, 11 microM; 2.1-fold stimulation over basal), although the response observed was markedly down-regulated compared with the response seen in noncultured airway smooth muscle preparations. Growth arrest of cells failed to increase the magnitude of the inositol phosphate response to carbachol. These results demonstrate that cultured human airway smooth muscle cells express functionally coupled M2 receptors and probably also low levels of coupled M3 receptors.
在培养的人气道平滑肌细胞中，研究了[3H] - 肌醇磷酸的形成以及毒蕈碱激动剂卡巴胆碱对异丙肾上腺素诱导的[3H] - 环磷酸腺苷（AMP）形成的抑制作用。用卡巴胆碱刺激可产生浓度依赖性地抑制异丙肾上腺素（1 microM）诱导的环AMP形成（EC50，0.15 microM；最大抑制率，60%）。该反应本身可被百日咳毒素（100 ng/ml）逆转，并被毒蕈碱拮抗剂哌仑西平（pA2，�.5）、甲溴东莨菪碱（pA2，8.0）、4 - 二苯基乙酰氧基 - N - 甲基哌啶（pA2，8.0）和对氟六氢硅二苯胺（pA2，6.5）竞争性抑制，表明M2受体亚型介导了该反应。此外，卡巴胆碱还诱导这些细胞中[3H] - 肌醇磷酸的形成（EC50，11 microM；比基础水平刺激2.1倍），尽管观察到的反应与未培养的气道平滑肌制剂中所见的反应相比明显下调。细胞生长停滞未能增加对卡巴胆碱的肌醇磷酸反应幅度。这些结果表明，培养的人气道平滑肌细胞表达功能偶联的M2受体，可能还表达低水平的偶联M3受体。
