RESUMO
A deficiency of the pulmonary vasodilative vasoactive intestinal peptide (VIP) has been suggested to be involved in the pathophysiology of pulmonary hypertension (PH). Supplementation of VIP as an aerosol is hampered by the fact that it is rapidly inactivated by neutral endopeptidases (NEP) located on the lung surface. Coapplication of thiorphan, an NEP 24.11 inhibitor, could augment the biological effects of inhaled VIP alone. A stable pulmonary vasoconstriction with a threefold increase of pulmonary artery pressure was established by application the thromboxane mimetic U46619 in the isolated rabbit lung model. VIP and thiorphan were either applied intravascularly or as an aerosol. VIP caused a significant pulmonary vasodilation either during intravascular application or inhalation. These effects were of short duration. Thiorphan application had no effects on pulmonary vasoconstriction per se but significantly augmented the effects of VIP aerosol. Thiorphan, not only augmented the maximum hemodynamic effects of VIP aerosol, but also led to a significant prolongation of these effects. VIP causes pulmonary vasodilation in a model of acute experimental PH. The hemodynamic effects of VIP aerosol can be significantly augmented via coapplication of an NEP inhibitor.
