Renin-angiotensin and sympathetic nervous system activity were evaluated in grade school children selected from the upper 0.26% and lower 5% of the blood pressure distribution constructed from a survey in the Minneapolis Public Schools. Eleven children from the upper 0.26% group and 19 children from the lower 5% group were admitted to the Clinical Research Center for 5 days and maintained on a 110 mEq sodium and 75 mEq potassium diet. On the fifth hospital day blood samples were obtained

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... after 2 hours of upright posture and after treadmill exercise. Mean sodium and potassium excretion and serum sodium and potassium were similar between the two groups. Plasma norepinephrine was not significantly different between the two groups at any of the three sampling times. Plasma renin activity was significantly lower in the upper 0.26% group in the supine and 2-hour upright samples. Mean plasma aldosterone (measured only in the supine blood samples) was not significantly different between groups. Plasma aldosterone values were significantly correlated with plasma renin activity only in the lower 5% group (r = 0.67, p < 0.005). This study suggests that in grade school children sympathetic nervous system activity is similar between children with high and low blood pressure but that plasma renin activity is lower and an apparent dissociation between plasma aldosterone and renin activity exists in the high blood pressure group. These findings should be confirmed in studies with larger numbers of subjects selected from the entire distribution of blood pressure. (Hypertension 4: 299-306, 1982) KEY WORDS • renin-angiotensin system childhood blood pressure norepinephrine • aldosterone • hypertension From the Division gation of patients within this age group in an attempt to define determinants of essential hypertension. The sympathetic nervous and renin-angiotensin systems are known to play a prominent role in the maintenance of blood pressure homeostasis. Because of this relationship, attempts have been made to correlate activity within these systems to the development of essential hypertension. In the spontaneously hypertensive rat model of genetic Hypertension, plasma and kidney renin activity and plasma and tissue levels of norepinephrine (NE) appear to be age-dependent and to differ significantly from levels in control normotensive rats.' In humans it has been suggested that increased levels of plasma catecholamines 10 " 11 or increased sensitivity to N E " may be associated with the presence of essential hypertension and that patterns of plasma renin activity (PRA) correlate with sympathetic nervous system activity and may affect the development of essential hypertension." Recently, it has been reported that differences in plasma N E between normotensive and hypertensive subjects can be detected as early as the second decade of life. 1 ' In the present investigation, renin-angiotensin-aldosterone and sympathetic nervous system activity were 299 by guest on July 22, 2018 http://hyper.ahajournals.org/ Downloaded from