Effect of Chronic Inhibition of Converting Enzyme on Renal Handling of Salt and Water: A Study on a Pediatric Population

Abstract

Background/Aims: The effect of angiotensin-converting enzyme inhibition (ACEi) is amply documented in several pathological conditions. However, there are few reports about the effect of chronic ACEi on salt and water balance. The present work evaluates the effect of chronic ACEi on salt and water balance in a population of children receiving enalapril chronically in order to reduce albuminuria elicited by a uremic hemolytic syndrome. Methods: Nine children aged from 9 to 19 years with normal glomerular filtration rate, normotension and with urinary concentration capacity preserved were treated with enalapril with doses ranging between 0.1 and 0.30 mg/kg/day. Diuresis, urinary absolute and fractional excretion of Na⁺, K⁺ and urea, creatinine clearance, osmolal clearance and tubular water reabsorption were measured under three experimental procedures: (1) with free access to water; (2) with a water load and (3) with water restriction. In the last group urinary antidiuretic hormone (ADH) was measured. These tests were performed in a paired way, just before starting ACEi treatment and after 6 months of enalapril treatment. Results: Enalapril treatment diminished the urinary concentration capacity without affecting Na⁺ and K⁺ urinary excretion. Creatinine clearance was not modified except in the condition of water load where a fall in it was found after ACEi. ADH increased after enalapril treatment in children under water restriction. Conclusion: In these children chronic ACEi decreases urinary concentration capacity.