CIRCULATING ADRENALINE IS NOT INVOLVED IN THE CIRCADIAN BLOOD-PRESSURE PROFILE

Background: Circadian changes in blood pressure are paralleled by anal ogous circadian changes in plasma catecholamines: blood pressure, plas ma noradrenaline and adrenaline fall at night. Objective: To determine whether adrenaline is a prerequisite for the nocturnal fall in blood pressure, the circadian blood pressure profile was studied in adrenale ctomized subjects, lacking circulating adrenaline. Subjects and method s: Ten adrenalectomized subjects and 10 healthy age-matched normotensi ve controls underwent 24-h non-invasive ambulatory blood pressure moni toring with the Oxford Medilog device. Measurements were taken every 1 5 min from 7.00 a.m. until 11.59 p.m and every 30 min from 12 midnight until 6.59 a.m. The nocturnal blood pressure fall was calculated for each subject. Results: Mean+/-SD systolic blood pressure decreased at night by 13.2 +/- 9.5 mmHg in the adrenalectomized and by 11.7 +/- 7.3 mmHg (NS) in the control subjects. There was no significant differenc e between groups in the nocturnal diastolic blood pressure fall (14.4 +/- 5.1 and 13.1 +/- 5.2 mmHg, respectively). Systolic blood pressure decreased by > 10 mmHg in five of the adrenalectomized and six of the control subjects. Diastolic blood pressure decreased by > 10 mmHg in e ight of the adrenalectomized and eight of the control subjects. Conclu sion: The normal nocturnal fall in blood pressure in adrenalectomized subjects indicates that circulating adrenaline is not required for a n ormal circadian blood pressure rhythm.