Changes in ECO and AR with inhibition of HO. A. Exhaled CO (ECO) changes with inhibition of heme-oxygenase by tin protoporphyrin (SnPP) without induction of airway inflammation (OVA, i.p.) and with airway inflammation (+OVA aerosol), in C57Bl6 mice, expressed as fraction of naïve (-OVA) controls (dashed line average = 2.3 ppm ECO, as shown in Figure 2A). *P < 0.05 vs. both naïve baseline and respective strain OVA sensitized-only (i.p.) group; n = 4/bar. B. Airway responses (Penh) to methacholine (MCh) aerosol in C57Bl6 mice either naïve (filled square ; n = 11); with airway inflammation (+OVA) +DMSO vehicle (filled circle; n = 6); or with airway inflammation + SnPP/DMSO (inverted filled triangle; n = 4); *P < 0.05 increased vs. naïve at same MCh concentration.