Differences between supine and sitting Frank-lead electrocardiograms

In babies ranging in age from 1 to 25 weeks and in children between 1 and 14 years, plasma renin activity and urinary aldosterone activity were determined in relation to urinary sodium excretion. A reciprocal correlation was found demonstrating that the hyperactivity of the renin-angiotensin-aldosterone system is stimulated in infants by a low sodium intake. A second stimulus was observed in the influence of the hypothalamo-neurohypophyseal system, when the plasma renin activity was suppressed by administration of antidiuretic hormone and sodium excretion increased due to a decreased aldosterone activity. Our study suggests that there exists a feedback between the renin-angiotensin-aldosterone system and ADH release and that this feedback plays an important role in the regulation of water and electrolyte balance in the young infant.