Phospholipid synthesis in isolated perfused lungs of rats made tolerant to 100% oxygen

Tolerance to 100% oxygen is readily induced in the rat by prior exposure to 80% oxygen for 7 days. In order to determine whether the rate of synthesis, or te alveolar content, of pulmonary phospholipids is altered in the tolerant rat, we perfused the isolated lung with medium containing 20 muM [14C]methyl choline chloride for 30 min at 10 ml/min, and then we measured the incorporation of carbon-14 into tissue phospholipids. We also measured the phospholipids in the lavage. There was no difference in the rate of incorporation in the tolerant rats (201 +/- 11 nmol/g dry lung, n = 8, mean +/- SEM) compared to control rats (210 +/- 9 nmol/g dry lung, n = 4) that had been exposed to air for 7 days under identical conditions. Whereas the induction of tolerance did not alter the total amount of phospholipid lavaged from the lung (tolerant: 251 +/- 31 microgram lipid phosphorus/g dry lung, n = 10; control: 228 +/- 9, n = 5) or the amount that was disaturated (tolerant: 44.7 +/- 4.2%, n = 5; control 45.0 +/- 2.1%, n = 4), there were marked increases in the relative amounts of phosphatidylcholine and phosphatidylethanolamine in the lavage from tolerant rats. Static compliance measurements revealed that the pressure required to maintain the tolerant lungs at 50% of total lung capacity was half that required in the control rats. At this stage it is not possible to say what role, if any, these changes have in the induction of tolerance to 100% oxygen.