Systemic factors in esophageal mucosal protection.

Blood bicarbonate is an important systemic factor in esophageal protection due to its capacity for buffering H+ either in the lumen, at the epithelial surface, within the intercellular space, or within the cell. The ability to buffer within the lumen is in part dependent on submucosal gland secretion, while buffering in the intercellular space depends on bicarbonate diffusion from blood, and intracellular protection depends on the presence of basolateral membrane bicarbonate transport via a mechanism such as the Na(+)-dependent Cl-/HCO3- exchanger.