Journal of Clinical Endocrinology & Metabolism, Vol 75, 1017-1021, Copyright © 1992 by Endocrine Society
Abnormal norepinephrine and aldosterone responses to upright posture in nonmodulating hypertension
PR Conlin, LM Braley, AI Menachery, NK Hollenberg and GH Williams
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
The subgroup of patients with nonmodulating hypertension demonstrates a
number of abnormalities of the renin-angiotensin-aldosterone axis. We
previously identified abnormalities in plasma and urinary dopamine in
nonmodulators and posited that this may be in part due to a generalized
defect in sympathetic nervous system activity. In the present study we
assessed the state of activation of the renin-angiotensin system and the
sympathetic nervous system in normal subjects and patients with modulating,
nonmodulating, and low renin essential hypertension during sodium depletion
and change from supine to upright posture. Levels of plasma norepinephrine
were higher in non-modulators during the posture study (P < 0.05). PRA
rose with upright posture in all groups, but low renin subjects had a
blunted response. Nonmodulators and low renin subjects had lower
aldosterone levels both supine (P< 0.05) and upright (P< 0.01).
However, the aldosterone/PRA increment ratio was increased in low renin
subjects (P< 0.01), whereas it was decreased in nonmodulators.
Twenty-four-hour urine collections for catecholamine determinations were
obtained in a subgroup of the subjects, with nonmodulators showing higher
levels of norepinephrine excretion which approached significance (P =
0.08). In vitro experiments using rat and human adrenal glomerulosa cells
showed that norepinephrine does not affect aldosterone secretion per se.
These observations extend the series of abnormalities observed in
nonmodulating hypertension. However, it is likely that the alterations in
norepinephrine levels during sodium depetion and upright posture are a
secondary event and not linked to the altered aldosterone production in
these patients.