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

The effects of dietary sodium intake on the renal excretion of urodilatin and of sodium were examined in six healthy male subjects. The 24-day 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 first phase, 5.6 mequiv (kg body weight)(-1) day(-1) during the second phase, and 8.4 mequiv (kg body weight)(-1) day(-1) during the third phase. 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 with 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 increased 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 renal natriuretic peptide, urodilatin, but not the main cardiac member of the natriuretic peptide family may be involved in the regulation of day-to-day sodium balance.