Edema in childhood nephrotic syndrome: possible genes-hormones interplay.

Background: The role of atrial natriuretic peptide (ANP) in edema formation in idiopathic nephrotic syndrome (INS) was studied before with conflicting results reported; however, the possible contribution of genes regulating ANP expression and receptors was never explored.

Methods: One hundred children (60 with active INS and 40 in remission) were studied for plasma atrial natriuretic peptide (ANP), urinary sodium, ANP gene A2843G and ScaI polymorphisms, and natriuretic peptide receptor clearance C (-55) A polymorphism. For comparative purposes, 20 healthy controls were studied for ANP levels.

Results: ANP was higher in active compared to remission patients (p<0.001). ANP in the healthy control group was significantly lower than the ANP level of active INS (during edema) group (p=0.009) but did not show significant differences when compared to ANP levels of either active INS group after resolution of edema or remission group (p= 0.42 and 0.56, respectively). Urinary sodium levels in edematous patients were significantly lower while ANP levels were significantly higher during edema than after resolution (p< 0.001 for both). Genotypes' frequencies of studied polymorphisms did not differ between active and remission groups. Patients with the A1A1 genotype of ScaI polymorphism had higher ANP levels compared to other genotypes (p =0.01).

Conclusions: During edema, ANP levels are elevated in INS children however this increment is not associated with natriuresis suggesting a blunted renal response to ANP. Polymorphisms of genes regulating ANP levels and receptors don't seem to be implicated in edema formation except for the A1A1 genotype of ScaI polymorphism however, its possible role needs further evaluation.