E. Fadel et al., Endothelial nitric oxide synthase function in pig lung after chronic pulmonary artery obstruction, AM J R CRIT, 162(4), 2000, pp. 1429-1434
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.