[13C]bicarbonate kinetics in humans: intra- vs. interindividual variations

Area of Science:

• Physiology
• Biochemistry
• Metabolic Studies

Background:

• Bicarbonate (HCO-3) kinetics are crucial for understanding metabolic processes, particularly nutrient oxidation.
• Accurate kinetic parameters and their variability are needed for designing and analyzing future studies.

Purpose of the Study:

• To conduct a multicompartmental analysis of bicarbonate kinetics in normal adults.
• To determine inter- and intraindividual variations in bicarbonate kinetic parameters.
• To provide data for future nutrient oxidation studies.

Main Methods:

• Administered a sodium bicarbonate (NaH13CO3) bolus intravenously to five normal adults.
• Analyzed 13C enrichment decay in breath CO2 using a multicompartmental model.
• Assessed bicarbonate pools, CO2 output, flux, and recovery rates.

Main Results:

• Bicarbonate kinetics were described by a three-exponential decay and a linear term.
• Identified central and peripheral bicarbonate pools with specific volumes.
• Found similar within-subject and among-subject variances for key kinetic parameters.

Conclusions:

• Population mean values for bicarbonate kinetics are comparable to repeated individual measurements.
• No significant advantage in repeated measurements on different days versus using population values.
• Compiling population values across diverse states is recommended for interpreting nutrient oxidation data.