The relationship between kidney function and plasma immunoreactive atrial natriuretic factor (irANF) levels as well as the effects of synthetic human ANF-(99-126) were investigated in 13 patients with mild to moderate chronic renal failure. Under basal conditions, glomerular filtration rate averaged 39 ± 5 (SEM) ml/min/1.73 m 2 and blood pressure (BP) averaged 166/107 ± 7/2 mm Hg; 12 patients were hypertensive. Plasma irANF levels were significantly increased (98 ± 16 vs 42 ± 4 pg/ml in healthy

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... control subjects; p< 0.001) and correlated (p< 0.05-0.005) inversely with hematocrit (r = -0.65) and positively with systolic BP (r = 0.75) or fractional sodium excretion (r = 0.75). Human ANF-(99-126) infusion for 45 minutes at 0.034 /ig/kg/min augmented (p< 0.05-0.01) diuresis and urinary sodium, chloride, calcium, phosphate, and magnesium excretion. During the subsequent 45 minutes of human ANF-(99-126) infusion at a rate of 0.077 /i.g/kg/min, diuresis and electrolyte excretion remained elevated (p<0.05-0.01). Glomerular filtration rate and effective renal plasma flow were not significantly modified, but filtration fraction rose progressively (p<0.01). Human ANF-(99-126) infusion decreased BP (p<0.05-0.01), produced bemoconcentration (hematocrit + 7%; p<0.01) without negative body fluid balance, and increased (p<0.01-0.001) plasma norepinephrine, insulin, and serum free fatty acids; plasma aldosterone and renin activity were unaltered during but rose after cessation of human ANF-(99-126) infusion. These findings indicate that circulating irANF increases in hypertensive patients with mild to moderate chronic renal failure and may support the homeostasis of sodium balance. Infused human ANF-(99-126) can acutely produce hemoconcentration, lower BP, induce sympathetic activation, stimulate plasma insulin, and augment the excretory function at least in part through tubular mechanisms. (Hypertension 11: 483-490, 1988)