Atrial natriuretic factor in the elderly: diminished response to epinephrine

Area of Science:

• Endocrinology
• Gerontology
• Cardiovascular Physiology

Background:

• Epinephrine (EPI) stimulates atrial natriuretic factor (ANF) release in young adults.
• Aging is associated with decreased sensitivity to adrenergic stimulation.
• Previous studies suggest age-related alterations in neurohormonal regulation.

Purpose of the Study:

• To compare plasma immunoreactive atrial natriuretic factor (irANF) responses to EPI infusion in young and elderly healthy subjects.
• To investigate the irANF response to saline infusion in elderly subjects.
• To assess age-related differences in adrenergic-stimulated ANF secretion.

Main Methods:

• Intravenous infusion of epinephrine (5 micrograms/min for 80 min) in six young (20-29 years) and nine old (62-75 years) healthy subjects.
• Measurement of plasma irANF and EPI levels before and after infusion.
• Infusion of 1 liter of normal saline over 30 min in the nine elderly subjects.

Main Results:

• Young subjects showed a significant increase in plasma irANF after EPI infusion (32 +/- 7 to 59 +/- 11 pmol/l, P < 0.02).
• Elderly subjects exhibited no significant change in irANF levels after EPI infusion (50 +/- 8 to 48 +/- 7 pmol/l), despite similar EPI levels.
• Elderly subjects demonstrated a marked increase in irANF following saline infusion (54 +/- 4 to 122 +/- 23 pmol/l, P < 0.01).

Conclusions:

• Healthy elderly subjects possess a defect in epinephrine-stimulated ANF secretion.
• This finding supports evidence of diminished adrenergic stimulation sensitivity in aging.
• The response to saline infusion suggests the defect is specific to EPI-mediated ANF release.