ENDOTHELIAL DYSFUNCTION IN VENOUS PULMONARY-HYPERTENSION IN THE NEONATAL PIGLET

In a group of neonatal piglets an increase in pulmonary arterial press ure was obtained within 2 weeks after a partial mechanical obstruction of the left atrium by a balloon catheter. Mean pulmonary artery press ure in the hypertensive animals (n = 6) was 24 +/- 2 mm Hg as compared (p < 0.01) with 15 +/- 1 mm Hg in controls (n = 6) or 9 +/- 2 mm Hg i n sham-operated piglets (n = 6). Cardiac index was reduced in hyperten sive versus control and sham groups: 0.15 +/- 0.01 versus 0.32 +/- 0.0 5 and 0.29 +/- 0.04 L . min(-1) . kg(-1) (p < 0.05), respectively. The re was no detectable difference on histologic examination in the pulmo nary arteries between the three groups. Right ventricular hypertrophy was observed in the group with pulmonary hypertension. In hypertensive piglets, isolated conduit pulmonary arteries did not relax when stimu lated with acetylcholine; they always relaxed to sodium nitroprusside. These data suggest that the first stages of perturbations reported du ring pulmonary venous hypertension occur at the level of the pulmonary vascular endothelium. This neonatal model of pulmonary hypertension i s simple to perform and might be useful for further investigations.