Does age increase plasma noradrenaline concentration through increased release or decreased clearance, and does this relate to blood pressure in healthy males?
Plasma noradrenaline concentration rises with age due to an increased rate of release rather than decreased clearance, but this increase does not correlate with higher blood pressure in the elderly.
Plasma noradrenaline concentration increases with age. This study was designed to investigate whether an increased rate of noradrenaline release into the circulation or a decrease in clearance is primarily responsible for this age related change in concentration. Sixteen healthy male subjects were studied, eight young (21-36 years) and eight old (65-78 years). Clearance was calculated from steady state noradrenaline concentrations during constant rate infusions of unlabelled noradrenaline. Clearance did not differ between the two groups: young 4.8 l/min (range 2.7-6.1), old 4.1 (range 2.6-8.2). The old subjects had significantly greater rates of release. Supine: young 10.3 nmol/min (range 5.3-17.6), old 19.7 (range 10.1-30), P less than 0.05. Standing: young 17.2 (range 11-36.4), old 29.2 (range 21.8-47.9), P less than 0.01. No significant relationship was found in either supine or standing position between rate of noradrenaline release and either systolic or diastolic blood pressure. These results indicate that plasma noradrenaline concentration rises with age because of an increased rate of release, but that this increased release is not responsible for the higher blood pressure seen in the elderly.
Rubin et al. (Thu,) studied this question.