[Twenty four-hour arterial blood pressure and urinary norepinephrine excretion rate in patients with essential hypertension].

Twenty four-hour blood pressure and heart rate were recorded with the Accutracker RII every hour automatically, and at the same time the urinary norepinephrine (NE) excretion rate (10.00-18.00, 18.00-22.00, 22.00-06.00, 06.00-10.00) were assessed by high performance liquid chromatography in essential hypertensive and normotensive subjects. In every time period, the absolute levels of arterial blood pressure and urinary norepinephrine excretion rate were higher in the essential hypertensive than in normotensive group. But both groups had a distinct circadian rhythm--nocturnal reductions of blood pressure, heart rate and urinary norepinephrine excretion rate. Correlation analyses confirm that arterial blood pressure was positively correlated with urinary norepinephrine excretion rate in every time period. Thus, persons with essential hypertension had similar circadian rhythm to that of normal subjects, but showed evidence of enhanced sympathetic nervous activity through out the 24-hour cycle. In addition, determination of urine NE excretion rate provides a handy and sensitive method for studying the role of peripheral sympathetic nerve in BP maintenance. As the relatively high level of NE and BP all occurred during the day time, we recommend that it could be used as an index to decide when to administer antihypertensive drugs.