The authors investigated the role of atrial natriuretic peptide (alpha-hANP 
99-126) in essential hypertension by evaluating some hemodynamic and renal 
effects of acute peptide infusion (1 micrograms/kg for 1 min + 50 ng/kg for the 
following 20 min) in fourteen subjects: eight mild to moderate, untreated, 
essential hypertensives (EH) and six normotensive (N) controls, during 2 
hour-clearance periods, the 1st after ANP infusion, the 2nd during placebo (PL) 
administration. The double-blind study was carried out after the patients had 
rested and fasted overnight. It showed no significant changes in heart rate 
(HR); instead, compared with placebo, mean blood pressure (MBP) decreased 
significantly in both groups, beginning from the 3rd min after ANP infusion was 
begun (N: PL = 87.04 +/- 1.7 mmHg, ANP = 80.9 +/- 3.7 mmHg, p less than 0.0001; 
EH: PL = 102.6 +/- 3.2 mmHg, ANP = 97.7 +/- 5.9 mmHg, p less than 0.01). Among 
the urinary parameters we considered, cyclic GMP (cGMP) increased after ANP 
infusion in all subjects (N: PL = 129.1 +/- 56.3 pmol/mL, ANP = 199.2 +/- 85.4 
pmol/mL; EH: PL = 106.55 +/- 56.2 pmol/mL, ANP = 220.03 +/- 92.7 pmol/mL, p less 
than 0.05); diuresis showed a prompt and significant increase in EH (N: PL = 837 
+/- 368 mL, ANP = 1066 +/- 340 mL; EH: PL = 713 +/- 286 mL, ANP = 1043 +/- 280 
mL, p less than 0.005), and so did natriuresis (N: PL = 23 +/- 14.3 mEq/L, ANP = 
33 +/- 14.6 mEq/L; EH: PL = 25.6 +/- 8.9 mEq/L, ANP = 41.9 +/- 13.8 mEq/L, p 
less than 0.01); urinary potassium excretion was significantly reduced in EH (N: 
PL = 18.7 +/- 12.9 mEq/L, ANP = 14.2 +/- 6.9 mEq/L; EH: PL = 16.5 +/- 7.9 mEq/L, 
ANP = 10.7 +/- 4.8 mEq/L, p less than 0.005), while no changes were noted in 
glomerular filtration rate (GFR), estimated as creatinine clearance, urinary 
magnesium, albumin and aldosterone excretion. To investigate other potential 
mechanisms involved in renal effects of ANP, the urinary excretion of both 
prostaglandins 6-cheto PGF1-alpha and thromboxane B2 (TXB2), and dopamine were 
studied. The results showed only a significant decrease of dopamine urinary 
excretion in EH after ANP administration (N: PL = 50.4 +/- 28.7 micrograms/L, 
ANP = 45.0 +/- 29.7 micrograms/L; EH: PL = 47.3 +/- 21.5 micrograms/L, ANP = 
27.1 +/- 12.7 micrograms/mL, p less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)