Carbachol-induced secretion and homologous desensitization in rat basophilic leukemia (RBL-2H3) cells transfected with human m2 muscarinic acet lcholine receptors

• Published in: Japanese Journal of Pharmacology 1995, Vol.67 (suppl.1), p.167-167
• Main Authors: Akihiro Sakurai, Tomokazu Yoshizumi, Kazuhiko Oishi, Masaatsu K. Uchida
• Format: Article
• Language: Japanese
• ISSN: 0021-5198

In order to investigate the mechanisms underlying the desensitization mediated through m2 muscarinic acetylcholine receptors (mAChs), RBL-2H3 cells, which secrete inflammatory mediators by aggregation of the high affinity IgE receptor but not by carbachol, were stably transfected with cDNA encoding the human m2 mAChRs. The transfected cells (RBL-m2) used here expressed mAChRs levels of B_max 2.3 Pmol/mg of membrane protein and K_d 0.024 nM, as assessed in saturation binding anaiysis using 「^^3 H」QNB. Like antigen, carbachol produced secretion from the transfected cells in a dose-dependent manner; 100 μM carbachol gave maximal secretion from spontaneous levels to 21%. The secretion was completely inhibited by 10 nM atropine, 30 ng/ml pertussis toxin, aud 1 mM LaCl_3 , indicating that the secretion is dependent on extracellular Ca^2+ and mediated through mAChs/pertussis toxin sensitive GTP-binding protein pathway. Exposure of the cells to 100 μM carbachol for 30 min in Ca^2+ -free medium inhibited the secretion induced by the subsequent addition of 10 μM carbachol plus Ca^2+ , whereas antigen-induced secretion was not influenced by the desensitizing treatment. These data indicate that the persistent stimulation of m2 ,mAChs results in homologous, but not heterologous desensitization of secretion in RBL-m2 cells.