Ranitidine is an anti-ulcer agent, that works through antagonizing the histamine H2 receptor. It is used to reduce abdominal pain, heartburn, acid indigestion and acid reflux. The pathway begins in the stomach, where ranitidine inhibits the histamine H2 receptor on the surface of the parietal cell. Now in the gastric endothelial cell, potassium-transporting ATPase units are inhibited by G-Protein signalling cascade through somatostatin receptor type 4, which is activated by somatostatin. At the same time, potassium-transporting ATPase is activated by the G-protein signalling cascade, through histamine H2 receptor which is inhibited by ranitidine, gastrin/cholecystokinin type B receptor, and muscarinic acetylcholine receptor M3 which are activated by histamine, gastrin and acetylcholine, respectively. The potassium transporting ATPase also converts water and ATP to a phosphate molecule and ADP. Alongside the transporters, potassium is brought into the cell. Carbonic anhydrase 1 uses water and carbon dioxide to create hydrogen carbonate and a hydrogen ion, which are both transported out of the endothelial cell, into the gastric lumen. A chloride ion is transported into the gastric endothelial cell through a chloride anion exchanger and is transported out of the cell through a chloride intracellular channel protein 2, back into the gastric lumen.

Ranitidine Pathway References

Gastric Acid Production References