Tyrosine-stimulated dopamine synthesis fails to affect urinary aldosterone and sodium relationship in normal weight and obese women

Abstract

The effect of L-tyrosine-induced increases in dopamine (DA) and norepinephrine (NE) turnover on the relationship between sodium and aldosterone excretion was assessed in normal weight and obese women adapting to a low sodium diet. During four continuous days, all study subjects consumed a liquid diet, Ensure ®, as the main nutrient source, which provided an average daily intake of 51 mmol sodium. In six normal weight controls, urinary DA and NE metabolites were unchanged while urine sodium decreased until balance was achieved and aldosterone increased. The inverse relationship between urinary sodium and aldosterone was also present in six normal weight subjects even after tyrosine-induced increases in the urinary DA metabolite, homovanillic acid (HVA), and in the NE metabolites, vanillylmandelic acid (VMA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG). Similarly, while tyrosine supplements increased urinary HVA and VMA in nine obese subjects, sodium and aldosterone remained inversely related. We conclude that tyrosine-induced variations in DA and NE synthesis and catabolism, as measured by urinary HVA, VMA and MHPG, have no effect on the expected relationship between urinary sodium and aldosterone or on the excretion of either one by obese and normal weight women, at least in the short term.