Fig. 1.

Changes in pulmonary artery pressure (PAP), expressed as percent change from baseline, in response to ACh (1 μg/kg), an endothelium-dependent agent, and inhaled nitric oxide (NO; 40 ppm), an endothelium-independent agent, in shunted lambs at 2, 4, and 8 wk of age. At 2 wk of age, PAP decreased significantly from baseline in response to ACh and inhaled NO. At 4 and 8 wk of age, PAP decreased significantly in response to inhaled NO but not to ACh. n = 5 for each group. Values are means ± SD. *P < 0.05 compared with baseline.