- Radioactive glucose was administered as an aerosol to isolated rabbit lungs in an artificial thorax in order to investigate the capacity of the lung tissue to metabolize substrate supplied via the airway rather than via the circulation. Comparisons were made with radioactive glucose to which insulin had been added, with aerosolized distilled water, and with lungs that were neither ventilated nor perfused. The lung tissue utilized the aerosolized glucose as substrate (linear production of 14CO2 incorporation into lipid, and maintenance of high-energy phosphate content). Addition of insulin to the glucose did not alter the values. Ventilation with aerosolized water instead of glucose significantly reduced high-energy phosphate content, and these values decreased significantly further when the lungs were not ventilated. These studies confirm the fact that substrate can be utilized from the airway side of the lung, and encourage the speculation that it might prove therapeutically useful in pulmonary failure.