Hormonal correlates of the inadequate natriuretic response to salt loading in idiopathic edema

The purpose of this study was to evaluate the body fluid and hormonal responses to salt loading in patients with idiopathic edema. In response to a combined intravenous and oral salt loading, patients with idiopathic edema were found, compared to control women, to have more weight gain, an increase in systolic and diastolic blood pressure, lower excretion of sodium and free dopamine (both the latter being partially accounted for by a diminished salt loading-induced increase in the creatinine clearance), and less plasma dopamine-beta-hydroxylase suppression. There were, between the groups, no differences in plasma and urinary concentrations of the dopamine precursor (dihydroxyphenylalanine), metabolites (dihydroxyphenyl-acetic and homovanillic acid, methoxytyramine and dopamine sulfate), or suppressibility of hormones which are under a partial dopaminergic inhibitory control (plasma renin activity, aldosterone and norepinephrine) by high salt. The inappropriate sodium retention, weight gain, and blood pressure increase following salt loading in idiopathic edema is thus associated with a blunted increase in the glomerular filtration and urinary dopamine excretion rates, as well as plasma dopamine-beta-hydroxylase non-suppressibility by saline. Some circumstantial evidence suggests that the dopamine deficiency is part of a wider disturbance within the cascade of natriuretic hormones.