Influence of sodium homeostasis and circadian rhythm on dopaminergic modulation of 18-hydroxycorticosterone secretion in man

James R. Sowers*, Naftali Stern

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

This study examines the effects of sodium homeostasis and circadian rhythm on plasma 18-hydroxycorticosterone (18-OHB) responses to the dopamine antagonist metoclopramide in seven normal individuals. Responses to metoclopramide were evaluated after receiving a 10-meq sodium diet, a 100-meq sodium diet, and a 200-meq sodium diet for 5 days. On all three occasions the subjects had reached sodium equilibrium states, as determined by urinary sodium measurements, at the time that they received metoclopramide. Percentageincremental 18-OHB responses to metoclopramide were greater (P < 0.01) in the subjects after 5 days on a 200-meq sodium intake than after 5 days on a 10-meq sodium intakeThe percentage increases in plasma 18-OHB after a 200-meq sodium intake were slightly greater (P < 0.05) than increases after a 100-meq sodium intake. Plasma 18-OHB levels demonstrated a circadian rhythm, with plasma levels reaching their zenith during the laterpart of sleep and shortly after awakening and reaching their nadir between 2000 and 2400hAlthough basal levels of 18-OHB at 2200 h (15.5 ± 1.6 ng/dl) were considerably lower (P < 0.01) than basal levels of 18-OHB at 0800 h, the 18-OHB responses to metoclopramide were similar at 0800 and 2200 h. Administration of the dopamine agonist bromocriptine (2.5 mg three times a day for 4 days) suppressed (P < 0.01) mean24-hplasma 18-OHB levels from 21.9 ± 2.0 to 14.8 ± 1.4 ng/dl. However, bromocriptine did not alter the circadian rhythm of 18-OHB secretion. These datasuggest that increased sodium intake leads to greater tonic dopaminergic inhibition of 18-OHB secretion. Although dopaminergic mechanisms modulate 18-OHB secretion, they do not governthe circadian rhythm of this corticosteroid.

Original languageEnglish
Pages (from-to)1046-1051
Number of pages6
JournalJournal of Clinical Endocrinology and Metabolism
Volume55
Issue number6
DOIs
StatePublished - Dec 1982
Externally publishedYes

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