Substrate metabolism in the perfused lung: response to changes in circulating glucose and palmitate levels

The effects of circulating levels of glucose and palmitate in the isolated perfused rat lung were investigated. Rat lungs were perfused for 1.5 hr with washed bovine erythrocytes (15% hematocrit) in Krebs-Henseleit bicarbonate buffer containing 5 g% bovine serum albumin. Glucose uptake in the perfused lung varied directly with circulating glucose concentration. Lactate production was affected proportionately more by high glucose levels than by low concentrations. Pyruvate production was decreased by both low glucose and palmitate concentration in the circulating medium. Oxidation of glucose to CO2 was depressed by low glucose and by high palmitate concentrations. Glucose incorporation into lung lipids was more strongly influenced by glucose concentration than by circulating palmitate levels. These data indicate acute changes in circulating levels of glucose and palmitate alone can act to either inhibit or stimulate glycolysis, glucose oxidation, and lipid synthesis in the perfused lung.