Blood pressure, heart rate, and plasma catecholamines in normal and hypertensive children and their siblings at rest and after standing.

Heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), plasma norepinephrine (NE), and epinephrine (E) levels at rest and in response to orthostatic stress of quiet standing were compared in 19 subjects with borderline hypertension (BH) (SBP-135 mm Hg, DBP-80 mm Hg), nine with significant hypertension (SH) (SBP-150 mm Hg, DBP-95 mm Hg), 14 normotensive siblings (NS) of hypertensives (SBP-113 mm Hg, DBP-64 mm Hg), and 21 age-matched normotensive controls (NC) (SBP-116 mm Hg, DBP-61 mm Hg). Group resting plasma NE levels were significantly higher in BH (454 pg/ml, p less than 0.001 pg/ml) and SH (384 pg/ml, p less than 0.01 pg/ml) than in NC (281 pg/ml) or NS (309 pg/ml), and more than 2 SD above the NC mean value in 50% of BH, 28% of SH, and 7% of NS. Plasma E levels were similar. On standing, mean arterial pressure (MAP) rose 13.7 mm Hg in NC, 3.9 mm Hg in BH, and 2.8 mm Hg in NS, and fell 7.3 mm Hg in SH. These differences reflect the frequent occurrence of hypotensive responses in study group subjects, which were not observed in NC. The mean rise in plasma NE with standing was blunted in hypertensives, increasing 40% to 50% compared with 95% in NC. In BH and NS, SBP was positively correlated with plasma NE levels at rest and with standing. These observations offer support for the hypothesis that altered adrenergic sympathetic nervous system (SNS) activity is present in a subgroup of young hypertensives and can be a contributing factor to their hypertension. Findings of similar SNS activity in some normotensive siblings suggest that genetic factors might be involved.