Exposure effects on surfactant metabolism. A, Protein expression profiles of surfactant-related proteins in the lung from the C57BL/6 and Apoe^−/− studies. The fold-change is color-coded and statistical significance is marked (BH-adjusted P-value, *< 0.05, ^x< 0.01). Missing values are gray. B, Comparison of lipid concentration profiles for the surfactant-associated PC and PG lipid classes. The mean and 95% confidence intervals of the measured lipid concentration are shown for the last time point of each study (7 months for the C57BL/6 and 8 months for the Apoe^−/− study). Only those lipid species with fatty acid chain compositions contributing at least 5% to the total lipid class concentration of either PC or PG are included. Missing bars indicate missing values, eg, for the C57BL/6 study no values were obtained for PG 16:0/20:4.