Renin-angiotensin and sympathetic nervous system activity in grade school children.

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Abstract
Renin-angiotensin and sympathetic nervous system activity were evalauted 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 [Minnesota, USA]. Children (11) 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 Na and 75 meq K diet. On the 5th hospital day blood samples were obtained supine, after 2 h of upright posture and after treadmill exercise. Mean Na and K excretion and serum Na and K were similar between the 2 groups. Plasma norepinephrine was not significantly different between the 2 groups at any of the 3 sampling times. Plasma renin activity was significantly lower in the upper 0.26% group in the supine and 2-h 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). In grade school children, sympathetic nervous system activity is similar between children with high and low blood pressure but 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.