Effect of oxygen exposure on ATP content of rat bronchoalveolar lavage

Exogenous ATP stimulates surfactant phospholipid secretion in vitro through binding to P2-purinoceptors on the surface of the alveolar type II cell. To determine whether ATP is present in the bronchoalveolar space at concentrations sufficient to stimulate phospholipid secretion, we determined bronchoalveolar lavage ATP content in rats exposed to different inspired oxygen concentrations. Bronchoalveolar lavage ATP content of control animals exposed to room air was 155 +/- 12 nmol ATP/lavage (n = 17) and fell in a dose-dependent fashion to 34 +/- 5 nmol ATP/lavage in animals exposed to 85% oxygen for 72 h (n = 17). Airway content of ATP metabolites fell in a similar fashion in response to oxygen exposure. The decrease in airway ATP content after oxygen exposure was also time-dependent. ATP content in young adult male rats exposed to 85% oxygen decreased from a mean of 236 nmol ATP/lavage on d 1 of exposure to 18 nmol ATP/lavage after 4 d. There was no further decrease in bronchoalveolar lavage ATP content after 4-7 d of oxygen exposure. Despite the fall in airway levels of ATP, disaturated phosphatidylcholine levels increased. Rat bronchoalveolar lavage contained measurable concentrations of ATP, indicating the presence of ATP in the airway at levels which modulate surfactant phospholipid secretion from isolated alveolar type II cells in vitro. Bronchoalveolar lavage ATP content decreased significantly with exposure to oxygen, whereas disaturated phosphatidylcholine content increased.