Renin-Angiotensin and sympathetic nervous system activity in grade school children

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 supine, 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.