Systemic and gastrointestinal bicarbonate buffer system

The systemic and gastrointestinal bicarbonate buffer system is a multi-component physiological mechanism essential for maintaining acid-base balance and mucosal integrity. It functions through the reversible equilibrium of carbon dioxide, water, and bicarbonate ions, a process primarily catalyzed by the carbonic anhydrase (CA) enzyme family and regulated by various ion transporters such as the SLC4 (bicarbonate transporters) and SLC26 families [1, 3]. Systemically, it serves as the primary extracellular pH buffer, neutralizing metabolic acids to maintain blood pH within the narrow physiological range of 7.35 to 7.45 [1]. In the gastrointestinal tract, bicarbonate is secreted by epithelial cells into the mucus layer to neutralize gastric acid, thereby protecting the stomach and duodenal lining from autodigestion and peptic ulceration [3]. Therapeutic targeting of this system involves direct supplementation with sodium bicarbonate for metabolic acidosis, the use of CA inhibitors like acetazolamide for glaucoma and altitude sickness, and the administration of antacids to manage gastric hyperacidity [2, 5]. Dysregulation of this system is a hallmark of metabolic acidosis, alkalosis, and various gastrointestinal disorders [1, 3].

Other names

Carbonic acid-bicarbonate buffer systemGastric mucosal bicarbonate secretionCO2/HCO3- buffer systemBicarbonate buffering mechanism

The mechanism involves the chemical neutralization of hydrogen ions by bicarbonate to form carbonic acid (subsequently CO2 and H2O), the enzymatic inhibition of carbonic anhydrase to reduce bicarbonate production or reabsorption, and the modulation of ion transporters (e.g., NHE3, CFTR, SLC4A4) to regulate bicarbonate flux across membranes [1, 2, 4].