1. For many years experimental evidence has suggested the existence of a circulating factor able to enhance sodium excretion.
2. Very recently peptides with natriuretic activity in experimental animals have been isolated from mammalian and human cardiac tissue. In order to determine whether this natriuretic activity has relevance to man we have studied the effects of an infusion of α-human atrial natriuretic peptide (α-h-ANP) in normal subjects.
3. Sodium excretion trebled (P = <0.005) during the infusion of a calculated dose of 15 pmol of α-h-ANP min−1 kg−1 and there was an accompanying diuresis; radioimmunoassay of plasma α-h-ANP during the natriuresis indicated a mean peak incremental concentration of 203 ± 78 (sem) pmol/l. The infusion of a calculated dose of 1.5 pmol min−1 kg−1 did not affect sodium excretion.
4. There were no haemodynamic changes and no side effects were noted.