PLASMA AND URINARY DIGITALIS-LIKE SUBSTANCE LEVELS DURING ATRIAL-NATRIURETIC-PEPTIDE INFUSION IN ESSENTIAL HYPERTENSIVE PATIENTS

In order to evaluate the effect of atrial natriuretic peptide (ANP) in fusion on plasma and urinary digitalis-like substance (DLS) levels, 18 essential hypertensive males (mean age 45.6 +/- 3.8 y) were studied. After 1 week on a normal NaCl intake (120 mmol/24h), patients were ran domly double-blindly assigned to receive either ANP (99-126) (0.3 mu g /kg/min) (number of patients = 10) or its vehicle (50 ml isotonic sali ne) (8 patients) over a period of 60 min, in supine position. Plasma a nd urinary DLS levels were measured at time -60, 0, 30, 60, 120, 180, and 240 min (infusion time from 0-60 min). During ANP infusion, plasma DLS levels decreased significantly (from 25.2 +/- 6.8 pg/ml at time 0 to 12.5 +/- 5.6 pg/ml at 60 min, p < 0.01), while urinary DLS excreti on increased (from 60.5 +/- 26.1 pg/ml at time 0 to 246.3 +/- 34.2 pg/ ml at 30 min, p < 0.0001; and 402.3 +/- 44.1 pg/ml at 60 min, p < 0.00 01). After 3 h from the end of ANP infusion, both plasma and urinary D LS returned to baseline levels (20.5 +/- 14.4 pg/ml and 84.5 +/- 34.2 pg/ml, respectively). Taken together, our data show that ANP infusion significantly increases urinary DLS excretion, while decreasing its ci rculating levels. This phenomenon could explain the different response of ANP and DLS to some stimuli, such as acute volume expansion. In fa ct, the rapid increment of plasma ANP due to an acute increase of extr acellular fluid volume might simultaneously inhibit the increase in ci rculating DLS levels by promoting the urinary excretion of this substa nce.