The effect of dietary sodium restriction on neurohumoral activity and renal dopaminergic response in patients with heart failure

Background: This work evaluates the effect of a low-sodium diet on clinical and neurohumoral parameters and on renal dopaminergic system activity in heart failure (HF) patients. Methods: We included 24 patients with mild-to-moderate stable HF with left ventricle ejection fraction <40%. Twelve patients were studied before and after a 15-day low-sodium diet; 12 maintained their usual diet. Serum sodium and creatinine, plasma l-DOPA, dopamine, its metabolites, BNP and aldosterone, and 24-h urinary sodium, creatinine, l-DOPA, dopamine and metabolites were measured. Results: The two groups were matched respecting to demographic and clinical parameters. Low-sodium diet caused significant reductions in weight, 24-h urinary volume and sodium and sodium fractional excretion. Renal delivery of l-DOPA and urinary excretion of l-DOPA significantly decreased while dopamine and metabolites were not affected. Urinary dopamine/l-DOPA and urinary dopamine/renal delivery of l-DOPA ratios increased, plasma l-DOPA decreased and plasma dopamine increased. Plasma aldosterone slightly rose, BNP decreased and noradrenaline and adrenaline increased. NYHA functional class was not affected by sodium restriction. Controls showed no differences. Conclusions: These results suggest that sodium restriction leads to activation of antinatriuretic antidiuretic systems in HF patients. However, renal ability to synthesize dopamine is increased in this condition, probably as a counter-regulatory mechanism.