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Characterization of HCO3-/CO2 pool sizes and kinetics in infants
Insights
Researchers quantified bicarbonate pool sizes in infants, providing crucial kinetic data for substrate oxidation studies. This study establishes foundational metabolic insights for infant research.
Area of Science:
- Biochemistry
- Pediatric Metabolism
Background:
- Interpreting substrate oxidation studies requires accurate bicarbonate pool sizes and kinetic data.
- Such data has not been previously established for infants.
Purpose of the Study:
- To determine bicarbonate pool sizes and kinetic data in fed, nonacidotic infants.
- To provide essential parameters for future substrate oxidation research in pediatrics.
Main Methods:
- Six infants (2.5-5 months old) received an intravenous bolus of sodium bicarbonate labeled with stable isotope 13C (NaH13CO3).
- Breath samples were collected over 240 minutes to measure the disappearance of 13CO2.
- Data were analyzed using a multicompartmental bicarbonate model.
Main Results:
- The mean sizes of three bicarbonate pools were determined: central (7.4 ± 0.8 mmol/kg), rapidly exchanging peripheral (15.1 ± 4.8 mmol/kg), and slowly exchanging peripheral (8.8 ± 3.5 mmol/kg).
- Mean percentage dose recovery of 13CO2 was 57 ± 10%.
- The determined pool sizes indicate significant metabolic exchange of carbon between bicarbonate and organic metabolites in infants.
Conclusions:
- This study presents the first quantification of bicarbonate pool sizes and kinetics in infants.
- The findings provide essential reference data for interpreting substrate oxidation studies in this age group.
- Results suggest extensive carbon exchange between bicarbonate and organic metabolites in the infant metabolic system.
Abstract:
The first bicarbonate pool sizes and kinetic data necessary for the interpretation of substrate oxidation studies have been determined in six fed, nonacidotic infants, ages 2.5 to 5 months. Following an intravenous bolus of NaH13CO3 (50 mumol/kg), breath samples were collected over 240 min for the analysis of breath 13CO2. Each breath 13CO2 disappearance curve was fitted to a multicompartmental bicarbonate model previously derived in adults. The mean sizes of the three bicarbonate pools were: 7.4 +/- 0.8 mmol/kg (central pool), 15.1 +/- 4.8 mmol/kg (rapidly exchanging peripheral pool), and 8.8 +/- 3.5 mmol/kg (slowly exchanging peripheral pool). The mean percentage dose recovery was 57 +/- 10%. The pool sizes suggested that extensive metabolic exchange of carbon between HCO3- and organic metabolites occurred in the infant.