LONG-TERM ELEVATIONS OF DIETARY-SODIUM PRODUCE PARALLEL INCREASES THERENAL EXCRETION OF URODILATIN AND SODIUM

The effects of dietary sodium intake on the renal excretion of urodila tin and of sodium were examined in six healthy male subjects. The 24-d ay study period was divided into three phases of 8 days each. Subjects ingested 2.8 mequiv sodium (kg body weight)(-1) day(-1) during the fi rst phase, 5.6 mequiv (kg body weight)(-1) day(-1) during the second p hase, and 8.4 mequiv (kg body weight)(-1) day(-1) during the third pha se. The excretion of both sodium (P < 0.002) and urodilatin (P < 0.006 ) increased in response to the increasing dietary sodium, while urine flow did not change. Urinary urodilatin excretion correlated closely w ith renal sodium excretion (P < 0.001). Serum aldosterone levels (P < 0.01) as well as serum renin levels (P < 0.05) significantly decreased with increasing sodium intake. Plasma [Arg]vasopressin levels increas ed significantly (P < 0.05). Plasma atrial natriuretic factor and cGMP levels as well as urinary cGMP excretion rates were unaltered by the changes in sodium intake. We conclude from these results that the rena l natriuretic peptide, urodilatin, but not the main cardiac member of the natriuretic peptide family may be involved in the regulation of da y-to-day sodium balance.