Proton pump inhibitor-associated pneumonia: Not a breath of fresh air after all?

Figure 1 Schematic diagram of the physiological control of the gastric parietal cell which secretes hydrogen ions into the gastric lumen. ECL Cell: enterochromafin-like cell; G (CCK2-B): gastrin-cholecystokinin-B receptor; H: Histamine; H2: histamine H2 receptor; M1, M3: muscarinic receptors; ATPase: H+/K+-ATPase proton pump; K+: potassium ion; H+: hydrogen ion; Open arrows: identify sites of action for antagonists; Four-pointed star: inactive pump; Five-pointed star: active pump; “+”: agonist; “-”: antagonist.