PlGF protein expression within the rat lung. Images (A-D) are taken from a normoxic lung, while images (E-J) are from a hypoxic lung. Panels A and E show low magnification images of control and hypoxic tissue. PlGF protein was expressed within the alveolar wall and type II pneumocytes (black arrows, B and F) and the wall of intra-acinar blood vessels (C and G). Panels (I) and (J) show PlGF stained and unstained macrophages from the same hypoxic lung (black arrows). A similar pattern of macrophage staining was observed in control lungs (not shown). Image (D and H) show normoxic (D) and hypoxic (H) lung tissue which was stained with a 1:10 dilution of primary antibody which had been pre-incubated with recombinant PlGF protein. Pre-incubation of the PlGF antibody with recombinant PlGF protein (R&D, UK) successfully blocked staining of the tissue therefore indicating that the staining observed is indeed specific for PlGF protein. All images were taken with an x100 objective, the scale bar represents 20 μm. (K) The volume fraction of PlGF protein was not altered following 14 days exposure to chronic hypoxia compared to its matched normoxic control. The black bar represents the mean value in each group. N = 7-8 per group.