Gastrointestinal HCO3− transport and epithelial protection in the gut: new techniques, transport pathways and regulatory pathways

The concept of a protective alkaline gastric and duodenal mucus layer is a century old, yet it is amazing how much new information on HCO3− transport pathways has emerged recently, made possible by the extensive utilization of gene-deleted and transgenic mice and novel techniques to study HCO3− transport. This review highlights recent findings regarding the importance of HCO3− for mucosal protection of duodenum and other gastrointestinal epithelia against luminal acid and other damaging factors. Recently, methods have been developed to visualize HCO3− transport in vivo by assessing the surface pH in the mucus layer, as well as the epithelial pH. New information about HCO3− transport pathways, and emerging concepts about the intricate regulatory network that governs duodenal HCO3− secretion are described, and new perspectives for drug therapy discussed.