Fig. 4.

Endothelial nitric oxide synthase (eNOS) or cyclooxygenase (COX) inhibition decreases bradykinin-induced pulmonary arterial relaxation. Dose-response curves of pulmonary arterial rings exposed to 10 pM to 1 μM bradykinin in an additive manner normalized to 10 µM phenylephrine (PE)-precontracted tension (%T_{10 μM PE}) for normoxic (A) and long-term hypoxia (LTH, B) sheep in the presence of DMSO (filled circles) for vehicle control and 100 μM N^G-nitro-l-arginine methyl ester (l-NAME, A and B, open circles, dotted line) for eNOS inhibition or 10 μM indomethacin (C and D, open circles, dotted line) to inhibit prostacyclin (PGI₂) production. Lines show resultant fits to the dose-response relationships with a Hill equation, and markers show means ± SE. The data were analyzed by 2-way analysis of variance with a Bonferroni posttest analysis for each dose. Statistical significance is noted relative to DMSO control, *P < 0.05, **P < 0.01, and ***P < 0.001. A: normoxic, n = 4/9; B: LTH, n = 7/15; C: normoxic, n = 3/11; D: LTH, n = 4/10.