Effects of Norepinephrine and Angiotensin II on Plasma Atrial Natriuretic Peptide Concentration in Humans

To clarify the effects of norepinephrine and angiotensin II (Ang II) on plasma atrial natriuretic peptide (ANP), both pressor substances were infused into normal volunteers, and plasma ANP levels and venous return were determined. When norepinephrine infusion elevated mean arterial pressure by 15 mm Hg, a transient increase of plasma ANP was observed. However, Ang II infusion showed no effect on plasma ANP levels, even though it also elevated arterial pressure. Superior vena cava flow and left atrial area, which were determined echocardiographically as the index of venous return, increased in the norepinephrine infusion study. However, in the study of Ang II infusion, there was no significant change in either superior vena cava flow or left atrial area. From these results, it was concluded that increased left atrial volume due to increased venous return is the major factor inducing ANP release in norepinephrine infusion.