Fig. 2

(a) Up-take and secretion of labelled surfactant protein B (SP-B) by primary human type II alveolar epithelial (AT2) cells. Labelled SP-B was added to the cells and a first uptake was observed at 0 min (a a), visualized as green staining in the cytoplasm. Five minutes after addition of a surfactant secretagogue (1-oleoyl-2-acetyl-sn-glycerol) which stimulates the secretion of SP-B, a decrease in the fluorescence was detected, and after 15 and 30 min the intensity of fluorescence further diminished (a b-f). (b) Levels of phospholipids (μM) measured in AT2 cell supernatants as compared to control medium. (c) Quantitative real time RT-PCR for gene expression of surfactant protein A (SP-A), surfactant protein B (SP-B), surfactant protein C (SP-C), and surfactant protein D (SP-D) by AT2 cells. Relative mRNA expression was normalized to GAPDH. Data are presented as mean ± SEM of independent experiments performed in four different cell lines. (d) SP-C protein expression in AT2 cells of two different donors (sample 1 + 2) was determined by western blot. β-actin served as control for equal protein loading. (e) Electron microscopy image of AT2 cells showing lamellar bodies (arrow)