Figure 1

Distribution of apolipoprotein C-II mRNA and protein in the mouse fetal lung. Mouse tissue sections are from pseudoglandular (GD 15.5, A, B, G, H), junction between pseudoglandular and canalicular (GD 16.5, I, J), or late canalicular (GD 17.5, C to F, K to N). In situ hybridization (above the yellow line) (A to F) was performed with apoC-II anti-sense (A, B, D to F) and sense (C) probes. A change in sites of apoC-II mRNA synthesis (positive signal, blue) according to developmental time was observed. Immunohistochemistry (below the yellow line) (G-N) was performed using an anti-apoC-II polyclonal antibody (H to L), an anti-cytokeratin 18 monoclonal antibody (N), or goat IgG as negative control (G, M). Positive signal (red) was found in the distal epithelium from GD 15.5 to GD 17.5, but it was found in secretory granule-like structures during the canalicular stage, but not the pseudoglandular stage. A transition state was observed on GD 16.5 (I, J). Scale bars, 50 μm (A, C, D, F to H, L, M), 20 μm (B, E, I to K), or 10 μm (N). A, artery; D, distal epithelium; M, mesenchyme; P, proximal epithelium; SM, smooth muscle; V, vein.