Clearance of vasoactive intestinal polypeptide (VIP) in the porcine pulmonary circulation

The clearance of vasoactive intestinal polypeptide (VIP) in the lung was determined in pigs. To measure the first pass uptake, a bolus of VIP (0.9 pmol·kg −1 and 9 pmol·kg −1) with an inert intravascular marker, indocyanine green (ICG), was injected into the right atrium. The percent uptake of VIP after the higher bolus, as estimated by comparing the levels of VIP and ICG in the pulmonary artery and the aorta, was 36 ± 6% during control infusion and 36 ± 13% during continuous infusion of VIP (3 pmol·kg −1·min −1). The VIP concentrations in the pulmonary artery and the aorta were not different under baseline conditions, but during continuous VIP infusion the levels of plasma VIP in the pulmonary artery were higher than those in the aorta (24.3 ± 1.6 pmol·l −1 and 20.4 ± 1.3 pmol·l −1, resp. P < 0.0001). These results indicate that the lung is not a source of plasma VIP, but the pulmonary circulation is a substantial contributor to the removal of VIP from plasma.