Monocrotaline pyrrole-induced structural changes in lungs from C57Bl 6 mice and Sprague Dawley rats. Representative histological pictures correspond to C57Bl 6 mice injected with DMF (vehicle) 28 days (A and G), MCTP 3 days (B and H), MCTP 7 days (C and I) and MCTP 28 days (D and J). Structural changes in rat lungs were assessed at 28 days after vehicle (E and K) or MCTP injection (F and L) Haematoxylin-Eosin staining is shown. Arrows indicate small pulmonary arteries. Scale bar = 50 μm.