(A–H) Immunohistochemical analysis of proSP-C, CC-10, α-SMA, and Pecam-1 in sections from Snx5+/+ and Snx5-/- lungs (n = 5). Scale bars: 50 µm. (A and B) proSP-C, a marker of surfactant protein C precursor in alveolar epithelial type II cells; (C and D) CC-10, a marker of Clara cells; (E and F) α-SMA, a marker of smooth muscle cells; and (G and H) Pecam-1, a marker of blood vessels, showed similar expression levels. The nuclei were stained with Hoechst. (I and J) Western blot analysis of proSP-C (I, n = 5) and Pecam-1 (J, n = 2) proteins in E18.5 Snx5+/+ and Snx5-/- lung whole lysates. (K) qRT-PCR analysis of surfactant proteins (SP-A, -B, -C, and -D) performed on RNA samples collected from total lungs (n ≥ 3). Similar expression levels of surfactants were seen. (L) Mature SP-B did not differ in Snx5-/- lungs (n = 5). (M) Sat PC were similar between Snx5+/+, Snx5+/-, and Snx5-/- mice (n = 6). (N) Transmission electron microscopy (TEM) of distal alveolar epithelial type II cells at E18.5. Apical microvilli (Mv; arrowhead), condensed lamellar bodies (LB), and secreted surfactants (Sf; arrow) were observed in Snx5-/- lungs. Scale bars: 2 µm.