Relationship between basal and sodium-stimulated plasma atrial natriuretic factor, age, sex and blood pressure in normal man.

The relationships between plasma atrial natriuretic factor (ANF), blood pressure (BP) and age have not been clearly defined. We measured plasma ANF levels and BP in 128 normal subjects (65 male; 63 female; mean age 48 years, range 20-87 years) on no medication. In subjects of 75 years or less (n = 120) plasma ANF was 5.7 +/- 0.3 pmol/l (mean +/- SEM). Plasma ANF did not differ between sexes (males 5.6 +/- 0.4 pmol/l, females 5.9 +/- 0.4 pmol/l). There was a positive correlation between plasma ANF and age, correlation coefficient (r) = 0.46, systolic BP (r = 0.44), diastolic BP (r = 0.22) and mean BP (r = 0.37) (all P less than 0.01), but after multiple linear regression analysis plasma ANF only related significantly (P less than 0.01) to age and systolic BP once other factors had been excluded. We also measured plasma ANF after erect and supine posture and during a 21IV normal saline infusion given over 4 hrs (n = 24; age range 21-62 years) after an overnight fast. Mean plasma ANF was 5.9 +/- 1.1 pmol/l erect, 7.4 +/- 1.6 pmol/l supine and rose to 10.1 +/- 1.4 pmol/l after saline (both P less than 0.05 vs basal). Response to saline was assessed as the area under the curve of hourly measurements. Neither this nor peak ANF during saline infusion correlated with age. We conclude that basal plasma ANF is influenced by age and systolic BP but plasma ANF response to acute saline stimulation is not.