ADRENOMEDULLIN DILATES THE PULMONARY VASCULAR BED IN-VIVO

The present study was undertaken to investigate the effects of adrenom edullin (ADM), a newly discovered peptide in normal human plasma, in t he pulmonary and systemic vascular bed of the intact cat. Because pulm onary blood flow and left atrial pressure were held constant, changes in lobar arterial pressure directly reflected changes in pulmonary vas cular resistance. Under conditions of resting (low) pulmonary vasomoto r tone, intralobar arterial bolus injections of ADM-(1 - 52) and two t runcated ADM sequences, ADM-(13 - 52) and ADM-(1 - 12), had little eff ect on baseline lobar arterial pressure. In contrast, when pulmonary v asomotor tone was actively increased by intralobar arterial infusion o f U-46619, intralobar arterial bolus injections of ADM-(1 - 52) (10-3, 000 ng) and ADM-(13 - 52) (10-3,000 ng) decreased lobar arterial press ure in a dose-dependent manner, whereas only the highest doses of ADM- (1 - 52) and ADM-(13 - 52) (1,000-3,000 ng) mildly decreased systemic arterial pressure. Under the same experimental conditions, injections of ADM-(1 - 12) had no effect on lobar arterial and systemic arterial pressures. The present data suggest that ADM-(13 - 52) or a similar AD M fragment is responsible for the marked pulmonary vasodilator activit y of ADM-(1 - 52) in vivo.