Velocity of CO2 exchanges in the lungs

Area of Science:

• Physiology
• Biochemistry

Background:

• Decade of research has advanced understanding of CO2 exchange kinetics in the lungs.
• Renewed interest in carbonic anhydrase (CA) function in lung and tissues, spurred by Roughton's hypothesis on blood pH equilibration.
• Significant new information on red cell membrane transport properties, particularly band 3-mediated anion exchange.

Purpose of the Study:

• To elucidate the kinetics of CO2 exchange processes in the lungs.
• To define the role and properties of lung carbonic anhydrase (CA) in CO2 exchange velocity.
• To understand the mechanisms of red cell anion exchange and its impact on CO2 transport.

Main Methods:

• Kinetic analysis of CO2 exchange component processes.
• Investigation of carbonic anhydrase (CA) location and kinetics in lung tissue.
• Characterization of band 3-mediated anion exchange pathway in red blood cells.
• Assessment of pharmacological agent effects on CA and anion exchange.

Main Results:

• Detailed kinetic properties of lung CA have been better defined, clarifying its role in CO2 exchange.
• Mechanisms of band 3-mediated electroneutral anion exchange are better understood, though often studied under non-physiological conditions.
• Pharmacological agents can detrimentally affect lung and red cell CA activity and red cell anion exchange kinetics.

Conclusions:

• Lung CA and red cell membrane transport are critical for CO2 exchange velocity.
• Kinetic data for red cell anion exchange often lack physiological relevance.
• The question of in vivo arterial blood pH disequilibrium in humans remains unresolved, highlighting the complexity of CO2 exchange mechanisms.