Antihypertensive and hypotensive effects of atrial natriuretic factor in men

Synthetic atrial natriuretic factor (ANF) was administered in ascending doses (0.03, 0.20, 0.45 microgram/kg/min) to eight mildly essential hypertensive men on high (200 mEq/day) or low (10 mEq/day) sodium diets. Responses of blood pressure, heart rate, urinary volume and electrolyte excretion, renin, and aldosterone were measured. For the entire group, ANF lowered blood pressure and increased heart rate during the 0.20 and 0.45 microgram/kg/min infusions, and the antihypertensive effect of the peptide persisted for at least 2 hours after the infusions ended. Four patients (2 at 0.20 microgram/kg/min and 2 at 0.45 microgram/kg/min) experienced sudden bradycardia and hypotension at the end of or shortly after completion of ANF infusion. Renal excretion of water, sodium, chloride, calcium, and phosphorus increased in a dose-dependent fashion in response to infused ANF. Patients on the 200 mEq/day sodium diet had greater increases in urinary volume (11.1 +/- 2.8 vs 3.0 +/- 2.0 ml/min; p less than 0.05), sodium (870 +/- 134 vs 303 +/- 27 microEq/min; p less than 0.05), and chloride (801 +/- 135 vs 176 +/- 75 microEq/min; p less than 0.02) compared with patients on the low sodium diet. The apparent direct suppressive effect of a 0.03 microgram/kg/min infusion of ANF on renin and aldosterone levels was overcome at higher doses by counterregulation provoked by the depressor action. Renin was slightly (-12%) suppressed during the 0.03 microgram/kg/min infusion of ANF but increased at the 0.20 (+50%) and 0.45 microgram/kg/min (+90%; p less than 0.03) rates. Aldosterone declined significantly during the 0.03 microgram/kg/min infusion (-45%; p less than 0.01) of ANF but not during the two higher dose infusions.(ABSTRACT TRUNCATED AT 250 WORDS)