Enhanced 24-hour norepinephrine and renin secretion in young patients with essential hypertension: relation with the circadian pattern of arterial blood pressure.

This study examines the possibility that 24-hour differences in blood pressure (BP) regulation between hypertensive and normotensive subjects is related to changes in 24-hour secretory patterns in circulating pressor hormones. Nine young subjects with normal BP and 9 patients with essential hypertension (EH) were studied during 24-hour recumbency. Every 20 minutes samples were taken to determine plasma norepinephrine (NE) levels and plasma renin activity (PRA). BP was measured every 20 minutes by automatic recording. A distinct circadian rhythm was demonstrated for mean BP, NE and PRA in both groups. Nocturnal reductions in mean BP, NE and PRA related best to the sleep-wakefulness cycle in both groups. Circadian changes in mean BP correlated with NE levels in both normal subjects and patients with EH. The most striking difference between the 2 groups was the absolute levels of mean BP, NE and PRA, which were higher in the EH group at most time points in the 24-cycle. Differences in levels of NE and PRA between the 2 groups were most accentuated during sleep. Thus, young persons with EH show evidence of enhanced sympathetic nervous activity throughout the 24-hour cycle, which is most pronounced during sleep. The multiple sampling approach offers a more sensitive indicator of the role of pressor hormones in BP maintenance.