Hormonal regulation of water metabolism in children with nephrotic syndrome

The roles of the antidiuretic hormone arginine-vasopressin (AVP), atrial natriuretic peptide (ANP), renin, aldosterone and catecholamines in the pathogenesis of impaired water excretion were studied in edematous children with nephrotic syndrome. Compared to non-proteinuric children with nephrotic syndrome in remission, edematous children during relapse had lower serum concentrations of sodium and chloride with lower plasma osmolality, but had higher hematocrit values (P less than 0.05, each). Plasma concentration of AVP was higher in edematous children (P less than 0.01). Compared to healthy, normal children, edematous nephrotic children had higher plasma concentrations of AVP, aldosterone, renin, noradrenaline, and adrenaline (P less than 0.01, each), but had similar levels of plasma ANP. Head out water immersion and infusion of 5 ml/kg 20% human serum albumin solution, both procedures known to increase central blood volume, resulted in a reduction of elevated hormone concentrations to near-normal levels and caused a rise in sodium and water excretion. Following albumin infusion, mean ANP rose fivefold, and plasma concentrations of this hormone correlated positively with urine flow (r = 0.64, N = 18, P less than 0.01) and with sodium excretion (r = 0.62, N = 18, P less than 0.01). It is concluded that AVP, renin, aldosterone and catecholamines are stimulated in edematous children with nephrotic syndrome by reduction in effective circulatory blood volume. Central blood volume expansion induced either by water immersion or by infusion of concentrated albumin solution is able to correct elevated hormone levels and to induce salt and water excretion. Plasma ANP appears to trigger the diuretic and natriuretic effects of central volume expansion.