Energy status of the rat lung after exposure to elevated PO2

To study hyperoxic effects on adenine nucleotide content and lactate and pyruvate production by lungs, rats were exposed to oxygen at 1 ATA for 18, 24, or 48 h or to 4 ATA for 1 h. Subsequently, lungs were removed from rats, placed in an isolated-lung apparatus, ventilated with 5% CO2 in O2, and perfused with Krebs-Ringer bicarbonate medium containing 5.5 mM glucose and 4% bovine serum albumin. Uptake of serotonin from the perfusate was depressed 28% in rats exposed to hyperbaric oxygen compared with unexposed controls. Concentrations of adenine nucleotides, the ATP/ADP ratio, and the "energy charge" were similar in control and oxygen-exposed rats. The production of lactate and the ratio of lactate to pyruvate production were significantly higher in rats exposed to oxygen for 48 h compared with other exposure regimens. Comparison of these results with those previously reported for serotonin uptake in lungs after hyperoxic exposure indicates that serotonin clearance is depressed prior to alteration of the energy status of the rat lung.