Glutamine metabolism by the endotoxin-injured lung

The alterations in lung glutamine (GLN) metabolism that occurs in the endotoxin-injured lung were studied in rats and subsequently correlated with flux changes that occur in patients with the adult respiratory distress syndrome (ARDS). Measurements in animals were made at various time-points following the administration of endotoxin, while studies in surgical patients were done in a group of healthy controls, in patients with "early" sepsis who had normal chest x-ray films, and in patients with radiographic and physiologic evidence of ARDS. In healthy control rats, net amounts of GLN are released by the lungs into the systemic circulation. This release rate doubled 30 minutes after intravenous endotoxin (1,580 +/- 320 nmol GLN/100 g BW/min vs. 736 +/- 179 in controls, p less than 0.01) but glutamine synthetase activity was unchanged, suggesting an outpouring of cellular glutamine stores. Two hours after endotoxin treatment, this accelerated fractional release of glutamine by the lungs was no longer detected. By the 12-hour time-point, the lungs reversed to an organ of net glutamine balance (234 +/- 248 nmol/100 g BW/min, p less than 0.05 vs. controls and ENDO30 min) despite a more than two-fold increase in glutamine synthetase activity (p less than 0.01). Simultaneously, lung weights were increased by 21% (p less than 0.01) and histologic examination showed an interstitial infiltrate and pulmonary edema. Similar observations were made in humans; patients with "early" sepsis exhibited a marked increase in lung glutamine release, while patients with ARDS demonstrated glutamine balance across the lungs (4,030 +/- 910 nmol GLN/kg BW/min vs. 637 +/- 496 in ARDS, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)