Elevated urinary excretion of endothelin-like immunoreactivity in children with renal disease is related to urine flow rate
Endothelin 1-21 belongs to a family of locally produced regulatory peptides with potent vasoconstrictor activity and profound renal effects. To study the biological significance of endothelin in children with renal diseases, we measured urinary endothelin-like immunoreactivity (ETir) excretion in children and adolescents (60 normal controls and 57 patients with renal disease). ETir excretion was constant during childhood and adolescence (4-18 years). Compared to these normal controls elevated urinary excretions of ETir were found in children with chronic renal failure, following renal transplantation and with idiopathic hypercalciuria (all groups p < 0.001). However, ETir excretion was unchanged in children with idiopathic steroid sensitive nephrotic syndrome, with stable chronic glomerulonephritis and in 4 patients with hemolytic uremic syndrome. Urinary ETir concentrations were similar in controls and in various patient groups. ETir excretion correlated positively with urine flow rate in normal controls (r = 0.71) and in all patients studied (r = 0.91). Fractional excretion of ETir correlated negatively with glomerular filtration rate. Eight healthy volunteers (23-27 years old, 4 female, 4 male) were studied before and after oral water load (20 ml/kg) to investigated the effect of ETir excretion on urine flow rate. Urine flow rose tenfold in response to water load and urine concentration of ETir fell only by factor 3 and urinary ETir excretion rose fivefold. These results indicate that urinary ETir excretion is related to and depends at least in part on urine flow rate. ETir excretion may so reflect a role of ETir in renal disease, especially in the diuretic state.