Renal adaptation to dietary sodium restriction and loading in rats treated neonatally with enalapril

Neonatal treatment of rats with angiotensin-converting enzyme inhibitors or the angiotensin II type 1 receptor antagonist losartan induces irreversible renal histological abnormalities, mainly papillary atrophy, in association with an impairment in urinary concentrating ability. In the present study, sodium and potassium balance were assessed during high and low sodium intake and dietary potassium restriction in adult Wistar rats treated neonatally with enalapril (10 mg x kg(-1) x day(-1)) from 3 to 24 days of age. During balance studies, neonatally enalapril-treated rats showed 1) normal adaptation to dietary sodium restriction, 2) sodium retention during dietary sodium loading, and 3) a transient, modest, renal potassium wastage during dietary potassium restriction. Renal clearance determinations under pentobarbital anesthesia showed elevated fractional excretions of sodium and potassium and osmolar clearance without changes in glomerular filtration rate or effective renal plasma flow in enalapril-treated compared with vehicle-treated rats. Thus, in addition to the impaired urinary concentrating ability, adult rats treated neonatally with enalapril demonstrated alterations in renal sodium and potassium handling, which may be related to the prevailing papillary atrophy.