Endothelial nitric oxide synthase function in pig lung after chronic pulmonary artery obstruction

Because long-term pulmonary artery (PA) obstruction is associated with expa nsion of the systemic blood supply to the lung, chronic ischemia may not oc cur, and endothelium nitric oxide synthase (eNOS) function may be preserved in postobstructive pulmonary arteries. To test this hypothesis, we studied piglets 2 d or 5 wk after left PA ligation or a sham operation. We measure d left lung ATP and lactate lung concentrations; calcium-dependent and calc ium-independent NOS activities and eNOS protein; and left PA relaxations in response to acetylcholine, calcium ionophore, and sodium nitroprusside. De creases in ATP and increases in lactate concentrations were significantly a ttenuated after 5 wk PA occlusion (p < 0.05 Versus sham and 2-d ligation). Compared with sham and 2-d PA occlusion, calcium-dependent NOS activity and eNOS protein were lower in the long-term PA occlusion group. Calcium-indep endent NOS activity was unchanged. Acetylcholine and calcium ionophore rela xations were impaired after 5 wk, whereas only acetylcholine relaxation was impaired after 2-d PA occlusion. Relaxation to sodium nitroprusside remain ed unchanged. In conclusion, despite relative conservation of lung energy m etabolism, prolonged PA occlusion decreased eNOS function and protein in po stobstructive pulmonary arteries.