CAT mRNA and protein expression. RT-PCR: (A) CAT mRNA was most abundant in the adult parenchyma, compared to neonates and the airway compartment. (B) Neonatal CAT mRNA is unaffected by PFP exposure. (C) Adult CAT expression was significantly decreased at PFP24 and 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) Representatively CAT and actin Western blots. (E) Neonatal CAT protein was unchanged post exposure. (F) Adult CAT protein expression trended upwards transiently 2 hours post exposure, but this interaction was insignificant. (G-J) Immunohistochemical localization of CAT protein (n=6 rats/group) in lung tissue: Under FA conditions, adults had more abundant CAT protein than neonates. Similar to western blotting, intense protein localization to both airway and parenchyma tissue was observed. Scale bar is 50 μm.