167 ALTERED SYMPATHETIC SYSTEM ACTIVITY IN A SUBGROUP OF JUVENILE ESSENTIAL HYPERTENSIVES AND SIBLINGS

Abstract

Hyperactivity of the sympathetic nervous system has been implicated in the pathogenesis of essential hypertension (E.H.). To evaluate sympathetic system activity (SSA) in EH in children, we compared Blood Pressure (BP) and heart rate (HR) with Plasma Norepinephrine (PNE) and Epinephrine (PEPI) levels measured by radioenzymatic assay in resting state (RES) and after postural challenge by standing 15 Min. (STD). Subjects include 21 normal controls (NC) 19 borderline hypertensives (BH), BP>90% for age, 9 significant hypertensives (SH) BP>95% for age and 14 normotensive siblings of Hypertensives (NS) 12-18 years of age. SH had higher RES HR (73±3/Min.) than NC (66±2/Min. p<.05). RES PNE levels were significantly higher in BH (455±37 pg/Ml) and SH (373±37 pg/Ml) than N.C. (281±12 pg/M1, p<.01) or NS (316±24 pg/M1). In 13 of 19 BH (67%), 5 of 9 SH (56%) and 6 of 14 NS (43%) RES PNE levels were above highest NC level (350 pg/Ml) identifying subgroups with increased SSA at rest among Hypertensives and Normotensive Siblings. With Hemodynamic response to STD HR in SH rose more (+22+2, p<.05) than NC (+13±2) and response of mean arterial pressure (NC +13.7±2 MM Hg) was blunted in BH (+3.9+2, SH (-7.3±3) and NS (+3±3 p<.01). Some Hypertensives and NS had a hypotensive response not seen in NC. Rise in PNE was blunted in BH and SH (+40% & +48%) compared with NC (+95%). PEPI levels rose more in BH and SH than NC. PNE levels were directly and significantly related to Systolic BP LY and STD in BH & NS, not in NC. Findings offer support for hypothesis that altered SSA contributes to presence of Hypertension in some young subjects. Presence of altered SSA in some NS of hypertensives could reflect a genetic factor accounting in part for their increased risk of developing E.H.

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