Figure 2: General mechanisms of Ca2+ handling in airway myocyte. SOC: store-operated channel. ROC: receptor-operated channel. VOC: voltageoperated channel. R: G-coupled membrane receptor. A: contracting agonist. PMCA: plasma membrane Ca2+ pump. NCX: Na+-Ca2+ exchanger. SR: sarcoplasmic reticulum. RyR: ryanodin receptor. InsP3R: InsP3 receptors. SERCA: SR Ca2+ pump. CaPr: Ca2+-binding protein. B and C: typical oscillating and non-oscillating Ca2+ signal of rat (B) and human (C) isolated ASMC in response to 30 sec ACh stimulation.