Changes in plasma immunoreactive atrial natriuretic peptide in response to saline infusion or to alterations in dietary sodium intake in normal subjects.

Plasma levels of immunoreactive atrial natriuretic peptide (irANP) have been measured in normal subjects in response to changes in sodium balance induced by either saline infusion or alterations in dietary sodium intake. In eight normotensive subjects, plasma levels of irANP (means +/- s.e.m.) increased from 5.8 +/- 0.9 to 15.8 +/- 4.4 pg/ml plasma after an infusion of isotonic saline (2 litres over a 60-min period). In seven subjects, plasma levels of irANP were measured on the 5th day of a low-sodium diet (10 mmol/day), a normal-sodium diet (150 mmol/day) and a high-sodium diet (350 mmol/day). Plasma levels of irANP increased with increasing sodium intake, with values of 4.0 +/- 0.9 (low-sodium diet), 6.9 +/- 1.3 (normal-sodium intake) and 12.1 +/- 1.8 pg/ml (high-sodium intake). These observations suggest that the atrial natriuretic peptides could be an important hormone system in the control of sodium excretion by the kidney, and thereby of sodium balance in normal man.