Lactate metabolism in perfused rat lung

Area of Science:

• Biochemistry
• Physiology
• Pulmonology

Background:

• The lung's metabolic capabilities, particularly its handling of glucose and lactate, are not fully understood.
• Investigating substrate utilization in the lung is crucial for understanding respiratory physiology and disease.

Purpose of the Study:

• To investigate glucose and lactate metabolism in isolated perfused rat lungs.
• To determine the lung's capacity for lactate production and utilization under aerobic conditions.
• To explore the potential of lactate as a substrate for lung lipid synthesis.

Main Methods:

• Isolated rat lungs were perfused with Krebs-Henseleit bicarbonate buffer.
• Perfusion media contained radiolabeled substrates: [U-14C]lactate, [U-14C]glucose, or [U-14C]alanine.
• Glucose uptake, lactate production, and substrate incorporation into lung tissues were quantified.

Main Results:

• Glucose uptake exhibited an apparent Km of 4.7 mM and Vmax of 107 µmol/g dry wt/h.
• Lactate production showed a Vmax of 82.9 µmol/g dry wt/h.
• The lung preferentially utilized lactate over glucose at equimolar concentrations and incorporated it into lipids, especially at high lactate levels. Fasting increased lactate production from non-carbohydrate sources like alanine.

Conclusions:

• The perfused rat lung actively produces and consumes lactate simultaneously under aerobic conditions.
• Lactate can serve as a substrate for lipid synthesis in the lung.
• Fasted lung tissue demonstrates an enhanced capacity for lactate production, potentially from non-carbohydrate precursors.