HMOX1 mRNA and protein expression. Animals were whole body exposed to FA or PFP for 6 hours, and sampled at 2, 24 and 48 hours post exposure; denoted as PFP2, PFP24 and PFP48. RT-PCR expression in airway and parenchymal compartments in neonatal and adult rats exposed to PFPs. (A) HMOX1 expression between compartments was similar in neonatal FA controls, but was greatest in adult parenchyma compared to both adult airways and neonatal parenchyma. (B) After PFP exposure, HMOX was transiently upregulated at PFP2 and PFP24 in the neonatal parenchyma. (C) Compared to neonates, adults had a delayed upregulated HMOX1 expression in the parenchyma that persisted to PFP48. Data are presented as mean+SEM (n=5-7 rats/group, in each compartment), * significantly different compared to neonates in the same compartment, † significantly different compared to airways in the same age, ‡ significantly different compared to FA in the same compartment. (D) Representative HMOX1 Western blot with actin loading control. (E) HMOX1 blots were quantified and revealed no exposure dependent effects in the neonatal lung. (F) HMOX1 protein expression trended upwards at 24 hours and reached statistical significance at PFP48. Data is presented as mean+SEM (n=6 rats/group) ‡ significantly different compared to FA in the same age. HMOX1 immunohistochemical detection of protein expression (n=6 rats/group) is presented in neonatal (G-H) and adult (I-J) of FA controls (G, I) and PFP48 (H and J) groups. HMOX1 protein was significantly enhanced in neonatal airways in the PFP48 group compared to FA. Additionally, robustly expressed HMOX1 protein was increased in both adult airways and parenchyma at PFP48 exposure. Scale bars are 50 μm.