The effects of incremental exogenous alpha-human atrial natriuretic factor (ANF) infusion (10 and 25 ng.kg-1. min-1) on the cardiovascular, renal, and hormonal systems were examined in 22 healthy males. Successive 45-min infusions of ANF increased plasma levels five- and ninefold from a basal 42 +/- 5 pg/ml (P less than 0.01 and P less than 0.001). Hemodynamic responses provoked by ANF consisted solely of progressive reductions in central venous pressure (CVP) (P less than 0.05). Heart rate and mean arterial pressure were unaltered. Plasma renin activity, aldosterone, and vasopressin were not modified by either dose of ANF. However, plasma norepinephrine increased 32% during the 10-ng.kg-1.min-1 infusion (P less than 0.05) and remained elevated during the higher dose of ANF. Renal function was unaltered by the 10-ng.kg-1.min-1 infusion of ANF when compared with base line and placebo responses. The 25-ng.kg-1. min-1 infusion of ANF increased sodium excretion 100% from base line (P less than 0.05), whereas potassium excretion decreased 47% (P less than 0.05). Urine output increased significantly from 7.7 +/- 0.6 to 12.5 +/- 0.7 ml/min (P less than 0.05). These responses were not observed in the placebo group or in an additional group of four volunteers who received a continuous low-dose infusion of ANF (10 ng.kg-1.min-1) for two consecutive 45-min periods. Neither dose of ANF altered creatinine clearance or free water clearance. The data indicate that fivefold elevations (physiological levels) of plasma ANF do not influence renal or hormonal function.(ABSTRACT TRUNCATED AT 250 WORDS)