Brain carbohydrate metabolism in developing rats during hypercapnia

The researchers used freeze-blowing to rapidly preserve rat brains. They employed [2-14C]glucose and [3H]deoxyglucose as metabolic tracers. Enzymatic techniques were used to analyze metabolite concentrations. The study compared normal and hypercapnic conditions in two age groups. The gas mixture for hypercapnia was 20% CO2, 21% O2, and 59% N2. Brain samples were obtained from 10- and 20-day-old rats. The researchers measured relative rates of isotope utilization. They tracked changes in intermediary metabolites under stress.

Normal glucose utilization tripled between 10 and 20 postnatal days. About 25% of 14C label from [2-14C]glucose was lost as lactate. Hypercapnia reduced glucose utilization by half in both age groups. Metabolite concentrations decreased progressively under high CO2 conditions. The data suggest lactate and glutamate may replace glucose as fuels. The Krebs cycle likely retained 75% of the 14C label in control groups. Hypercapnia caused similar proportional reductions in both age groups. The authors propose that endogenous metabolites supplement glucose during stress.

The authors suggest that developing rat brains respond to hypercapnia by reducing glucose use. They propose that intermediary metabolites compensate for reduced glucose availability. The study shows that 10- and 20-day-old rats respond similarly to high CO2. The researchers suggest lactate and glutamate may serve as respiratory fuels. The data support the idea that metabolic flexibility emerges early in development. The authors propose that intermediary metabolite oxidation increases under stress. They suggest that lactate loss is not the primary metabolic pathway. The findings imply that young brains adapt to environmental stressors through metabolic shifts.