Circadian variation in serum atrial natriuretic prohomones and blood pressure in aging male subjects

Atrial natriuretic peptides are a family of hormones synthesized within the same prohormone secreted mainly within the atrium of the heart. These peptides correlate inversely with blood pressure (BP) in humans throughout the day. The increase in BP with increasing age could thus be associated with a decrease in these hormones as the person ages. The present investigation was designed to determine if these peptides, i.e., long acting natriuretic peptide (LANP), vessel dilator (VSDL) and atrial natriuretic factor (ANF), exhibit differing circadian characteristics in men as a function of age. The LANP, VSDL, and ANF were obtained from blood sampled every 3-hr for 24-hrs in men housed in a hospital setting at 3 different ocassions, 5 years apart. Seven men were studied 3 times; 4 in 2 ocassions, and 4 participated once. BP was always obtained by ambulatory monitoring at 15-min intervals. Lights were off at 22:30 h and on at 06:30 h. Hospital meals (2400 cal) were served at 16:30, 07:30 and 13:30 h. Circadian characteristics of hormones and BP in groups of subjects divided by age (<55, 19 profiles; and >55 years, 14 profiles) were established by population multiple-component analysis [Fernández JR, Hermida RC. Chronobiol Internat 1998;15:191–204]. A significant high amplitude rhythm (P < 0.001) was demonstrated for the three peptides in each age-group, with highest values consistently obtained at about 05:30 h. Significant declines in daily mean and amplitude (P < 0.005) were noted in the older group for all three peptides. A highly significant inverse correlation was found between the values of the three peptides and systolic and diastolic BP (P < 0.007). LANP, VSDL, and ANF exhibit a highly significant circadian variation as well as a significant decline with age. The present findings indicate that these BP lowering hormones are present in high concentrations in the early morning hours and in significantly lower concentrations throughout the day, in keeping with their inverse relation with BP.