Activation of MAP kinases in alveolar macrophages from smokers and nonsmokers. AM from smokers and nonsmokers were cultures with LPS (1 µg/mL) from 0–30 min or with sorbitol (400 mM). Cell extracts were prepared and subjected to immunoprecipitation followed by SDS-PAGE and immunoblotting using monospecific antibodies as in Methods. (A) Activation of ERK. (B) Activation of SAPK. (C) Activation of p38. In A, B, and C, a representative experiment from one smoker and one nonsmoker is shown in the upper panel. In the lower panel, all data from smokers (n = 5) and nonsmokers (n = 5) were subjected to densitometric analysis. The ratio of MAP kinase activity of LPS stimulated/unstimulated cells was calculated and the mean ± SEM fold increase in MAP kinase activity, from all donors was subjected to statistical analysis by Student’s t test.