Modulation of ENO, ECO, and AR in NOS-2-/- mice. A. Changes in exhaled NO (ENO; open circle) and CO (ECO; filled circle) in NOS-2-/- mice (n = 4) 48 hr. after administration of S-methyl-L-thiocitrulline (SMTC). Open bar indicates median ENO value, black bar indicates median ECO value; *P < 0.05 vs. -SMTC. B. Changes in exhaled NO (ENO; open circle) and CO (ECO; filled circle) in NOS-2-/- mice (n = 3) 48 hr. after administration of tin protoporphyrin (SnPP). Symbols and bars as in panel A. C. Airway responses (Penh) to methacholine (MCh) aerosol in naïve NOS-2-/- mice treated with SMTC (open square n = 4) or SnPP (inverted open triangle; n = 3), and with allergic airway inflammation (+OVA, filled triangle, n = 8) as compared to naive NOS-2-/- mice with no treatment (open triangle; n = 8). *P < 0.05 vs. 0 mg/ml MCh, ^P < 0.05 vs. naive at same MCh concentration.