Plasma atrial natriuretic peptide concentration and platelet atrial natriuretic peptide binding site density in...

1. Ageing and hypertension are associated with changes in the way in which the body handles sodium. This may involve changes in plasma atrial natriuretic peptide concentration, since atrial natriuretic peptide is a regulator of sodium handling by the kidney and the plasma atrial natriuretic peptide concentration is increased in both ageing and hypertension. An increase in the plasma atrial natriuretic peptide concentration could also be associated with a change in atrial natriuretic peptide receptor density, possibly involving down-regulation. 2. To investigate these possibilities plasma atrial natriuretic peptide concentration and platelet atrial natriuretic peptide binding site density were measured in 18 young, 11 middle-aged and 12 elderly healthy subjects and in 23 patients with mild to moderate essential hypertension. 3. In normotensive subjects, the plasma atrial natriuretic peptide concentration increased with age (r = 0.49, P less than 0.01) and was significantly higher in elderly than young subjects (mean +/- SEM, 31.9 +/- 4.5 versus 18.3 +/- 2.0 pmol/l, P less than 0.05). The plasma atrial natriuretic peptide concentration increased with the mean arterial pressure in normotensive subjects (r = 0.47, P less than 0.01). Multiple regression analysis did not show independent relationships between the plasma atrial natriuretic peptide concentration and either age or mean arterial pressure in normotensive subjects alone. However, when normotensive subjects and hypertensive patients were considered together, multiple regression revealed both age and mean arterial pressure as independent predictors of the plasma atrial natriuretic peptide concentration (P less than 0.05, P less than 0.01, respectively). In normotensive subjects, the platelet atrial natriuretic peptide binding site density did not change with age (r = 0.19, P = 0.27).(ABSTRACT TRUNCATED AT 250 WORDS)