Cardiovascular, endocrine and renal effects of atrial natriuretic peptide in essential hypertension

Plasma concentrations of human atrial natriuretic peptide (hANP) and effects of synthetic alpha-hANP on blood pressure (BP), on endocrine and metabolic variables, and on renal function were investigated in 10 patients with essential hypertension. Alpha-human atrial natriuretic peptide was given intravenously as a 50-micrograms bolus followed by a 45-min infusion at 0.1 microgram/kg per min. The following effects were observed: (1) a marked rise in plasma alpha-hANP, (2) a progressive fall in BP (from 181/127 to 165/109 mmHg) and plasma volume, (3) a probably baroreflex-mediated sympathetic activation, evidenced by raised heart rate and plasma norepinephrine levels, (4) an increase in serum free fatty acids and circulating insulin (+45%), (5) an enhanced diuresis (+770%) and excretion of sodium (+665%), chloride (+524%), phosphate (+518%), other electrolytes, amino acids and free water clearance, (6) biphasic responses in the glomerular filtration rate (GFR) and p-aminohippurate (PAH) clearance, with initial increases (+40 and 30%, respectively) followed by a rapid return to (GFR), or even a fall below (PAH clearance) control values, and (7) a marked rise in the filtration fraction. Plasma antidiuretic hormone and urinary prostaglandin E2, F2 alpha and dopamine levels were not modified during alpha-hANP infusion, while plasma renin increased. Discontinuation of alpha-hANP was followed by rises in plasma aldosterone, the aldosterone:renin ratio and cortisol. Compared with previously studied normal subjects, in the hypertensive patients alpha-hANP caused a distinctly greater diuresis and electrolyte excretion but lowered BP only slightly more. In essential hypertension, as in normal man, alpha-hANP circulates in the blood and may exert a wide spectrum of cardiovascular, metabolic, endocrine and renal actions.