INHALED NITRIC-OXIDE REVERSES VASCULAR AND RESPIRATORY EFFECTS OF ET-1 AND PAF IN PIGS

In anaesthetized paralysed, mechanically ventilated pigs, the vascular and respiratory effects of 80 ppm nitric oxide (NO) inhaled for 6 min were evaluated. To evoke different levels of smooth muscle contractio n ET-1 or PAF, mediators involved in pulmonary disorders, were used. I n control conditions, inhaled NO caused selective pulmonary vasodilata tion without affecting respiratory resistances. This pulmonary vascula r activity influenced the distensibility of the respiratory system and decreased inspiratory work. ET-1 administration significantly increas ed pulmonary arterial pressure and modestly changed mechanical propert ies of the respiratory system, while PAF caused potent vasoconstrictio n and bronchoconstriction associated with a marked change in volume-pr essure relationship. In both cases, the changes in vascular and mechan ical properties of the respiratory system increased inspiratory work T he vascular and respiratory activities of inhaled NO were correlated w ith preconstriction levels. The data show that the combination of vasc ular and respiratory effects improves pulmonary function, suggesting t hat inhalation of NO is a possible therapeutic approach for obstructiv e and inflammatory pulmonary diseases.