RENAL ADAPTATION TO DIETARY-SODIUM RESTRICTION AND LOADING IN RATS TREATED NEONATALLY WITH ENALAPRIL

Neonatal treatment of rats with angiotensin-converting enzyme inhibito rs or the angiotensin II type 1 receptor antagonist losartan induces i rreversible 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 durin g high and low sodium intake and dietary potassium restriction in adul t Wistar rats treated neonatally with enalapril (10 mg.kg(-1).day(-1)) from 3 to 24 days of age. During balance studies, neonatally enalapri l-treated rats showed 1) normal adaptation to dietary sodium restricti on, 2) sodium retention during dietary sodium loading, and 3) a transi ent, modest, renal potassium wastage during dietary potassium restrict ion. Renal clearance determinations under pentobarbital anesthesia sho wed 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 r ats. 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 pr evailing papillary atrophy.