To examine the effect of age on the secretion and action of human atrial natriuretic polypeptide (hANP), we compared plasma atrial natriuretic polypeptide and cGMP concentrations in 19 normal young (24-28 yr old) and 31 elderly (64-91 yr old) men. The mean basal plasma hANP level was 25 +/- 5 (+/- SEM) pg/ml in the young men and 120 +/- 22 pg/ml in the elderly men (P less than 0.01). The molecular size of plasma hANP in an aged man was similar to that of alpha hANP. The responses of plasma hANP and cGMP concentrations to an iv infusion of 500 ml 0.15 M NaCl also was compared. Mean plasma hANP concentrations increased significantly in both groups, and the response in the elderly men was exaggerated compared to that in the young men. However, the increases in plasma cGMP concentrations during NaCl loading were similar in both groups. We conclude that 1) the plasma hANP concentrations in healthy elderly men are higher than those in young men, and 2) the higher plasma hANP concentrations may be a compensatory response to reduced hANP activation of its receptors.

The effects of ovine corticotropin releasing factor (o-CRF) on the secretions of ACTH, cortisol, dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S) were studied in the healthy young and elderly male individuals. o-CRF caused significant elevations of plasma ACTH, cortisol and DHEA concentrations, in all subjects. Moreover, there were no significant differences in the time-dependent responses of plasma ACTH, cortisol and DHEA to o-CRF between the young and elderly male individuals o-CRF showed no significant rise of plasma DHEA-S, in all subjects. We conclude that the pituitary-adrenal sensitivity to the hypothalamic CRF in the elderly does not change with aging.

No abstract

The synthetic alpha-human atrial natriuretic polypeptide (alpha-hANP) was infused into six normotensive, euvolaemic, healthy volunteers to examine the effect on the plasma arginine vasopressin (AVP) concentration. The intravenous administration of alpha-hANP (0.1 microgram/kg/min, 20 min) led to a remarkable reduction in mean blood pressure (-10 mmHg, P less than 0.05), and there was an increase in pulse rate (+10 bpm, P less than 0.05), in each subject. The urinary volume, sodium excretion and cyclic 3',5'-guanosine monophosphate (cyclic-GMP) excretion were increased to 3.5 (P less than 0.05), 2.5 (P less than 0.05) eight-fold (P less than 0.01), respectively, during the alpha-hANP infusion. The dose and duration of the synthetic alpha-hANP in the present study was sufficient to induce these cardiovascular and renal effects. The plasma AVP concentrations decreased from 0.39 +/- 0.09 pg/ml to the undetectable level during the alpha-hANP administration. After infusion, the plasma concentrations of the AVP promptly returned to preinfusion levels (0.46 +/- 0.14 pg/ml). However, there was no significant change in plasma AVP concentration during placebo infusion. The marked suppression in plasma AVP concentration may account for the remarkable diuresis, in addition of the direct renal effects of the synthetic alpha-hANP.