Extracellular bicarbonate buffer system (BBS)

The extracellular bicarbonate buffer system is the primary physiological mechanism for maintaining acid-base homeostasis in the blood and interstitial fluid (StatPearls, 2023). It operates through a reversible chemical equilibrium between carbon dioxide (CO2), water, carbonic acid, and bicarbonate ions (HCO3-), a process catalyzed by the enzyme carbonic anhydrase (National Center for Biotechnology Information, 2022). By shifting this equilibrium, the system can rapidly neutralize excess hydrogen ions or compensate for changes in CO2 levels via respiratory and renal regulation (Merck Manual, 2023). While the system itself is a physiological pathway rather than a single molecular target, its components—such as carbonic anhydrase and various bicarbonate transporters—are targeted by drugs like acetazolamide to treat glaucoma and altitude sickness (PubMed, 2021). Clinical management of acid-base disorders often involves direct supplementation with sodium bicarbonate to correct metabolic acidosis (NIH, 2022). Monitoring the components of this system, such as serum bicarbonate and pCO2, is vital for diagnosing and managing life-threatening respiratory and metabolic conditions (StatPearls, 2023).

Other names

Carbonic acid-bicarbonate buffer systemBicarbonate-carbon dioxide buffer systemBlood pH buffer systemBicarbonate buffer

The system is modulated by the direct administration of bicarbonate ions to increase buffering capacity or by the inhibition of carbonic anhydrase enzymes to decrease bicarbonate reabsorption and increase its excretion (StatPearls, 2023; PubMed, 2021).