PULMONARY VASORELAXANT ACTIVITY OF ATRIAL-NATRIURETIC-PEPTIDE AND BRAIN NATRIURETIC PEPTIDE IN HUMANS

Background - Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) exhibit in vitro pulmonary vasodilator activity, but little information is available regarding their effects in the human pulmonary vasculature. Their effects in the human pulmonary circulation and their ability to modulate the pulmonary presser effects of angiotensin II have therefore been evaluated. Methods - Eight healthy volunteers were studied on three separate occasions, Infusions of either ANP, BNP, or placebo were given for 60 minutes with a concomitant infusion of angiotensin II given for the final 30 minutes. Pulmonary haemodynamics were measured by pulsed wave Doppler echocardiography at baseline (T-0), before commencing angiotensin II (T-30), and at the end of the infusion period (T-60). Results - Mean pulmonary artery pressure (MPAP) showed a fall with ANP and BNP infusion at T-30 compared with placebo. Although angiotensin II infusion had significant pulmonary presser effects on all three study days, MPAP at T-60 was lower when ANP (18.3 (2.0) mm Hg) and BNP (16.1 (1.5) mm Hg) were given concomitantly compared with placebo (21.8 (1.6) mm Hg). Conclusions - These findings indicate that both ANP and BNP exhibit pulmonary vasorelaxant activity in humans in terms of antagonism of the pulmonary presser effects of angiotensin II. This would support the hypothesis that ANP and BNP act as circulating counter-regulatory hormones in states of pathological pulmonary vasoconstriction.