The hemodynamic and renal electrolyte/function effects of a synthetic peptide (ANF) corresponding to the sequence of the 26 amino acids contained in atrial natriuretic factor (ANF) were assessed in closed-chest dogs in which acute left ventricular failure was produced by coronary artery embolization with 50 micron plastic microspheres. Coronary embolization produced a sustained reduction in cardiac contractility (LV dP/dtmax) and cardiac output which averaged 42 and 44%, respectively. Following a 45 min equilibration period after heart failure induction, most of the hemodynamic functions stabilized. At this time, ANF infused intravenously at 100 pmol/kg per min X 30 min (n = 9) did not lower mean arterial pressure although it increased cardiac output (P less than 0.05) by 17% at only one time period. With the exception of a fall in coronary resistance and an increase in myocardial blood flow, a higher dose of ANF (200 pmol/kg per min) did not consistently alter hemodynamic function. Fractional excretion of sodium (FE Na%) increased 3.4-fold with ANF at 100 pmol/kg per min and 1.8-fold with the 200 pmol/kg per min dose. Neither dose of ANF produced significant effects on renal blood flow (RBF) or glomerular filtration rate (GFR). Plasma angiotensin II which was 91 +/- 20 fmol/ml at baseline increased to 175 +/- 25 fmol/ml (P less than 0.05) 45 min after heart failure induction. However, neither dose of ANF significantly reduced these high circulating angiotensin II levels. These results demonstrate that an infusion of a synthetic ANF stimulated saluresis without altering RBF or GFR, and improved cardiac output in dogs with acute left ventricular failure.