Hemodynamic and renal responses to physiological levels of atrial natriuretic factor in conscious dogs.

The effects of increases in plasma atrial natriuretic factor (ANF) similar to those encountered after rapid volume expansion were examined in conscious dogs. Hemodynamics and renal function were continuously monitored during 30 minutes of human ANF infusion (10 ng/kg.min) and throughout a 30-minute recovery period. Ten minutes into the infusion period, plasma levels of ANF were elevated (p less than 0.01) by 34 +/- 9 from 36 +/- 5 pg/ml and sodium excretion increased (p less than 0.05) by 34 +/- 7 from 67 +/- 9 mueq/min. At that time, urine flow did not differ from baseline (0.25 +/- 0.03 ml/min). Renal blood flow velocity fell (p less than 0.01) by 5.0 +/- 0.5 from 42.3 +/- 3.7 cm/sec. Thirty minutes into the infusion period, plasma ANF levels were increased (p less than 0.01) by 61 +/- 9 pg/ml, similar to levels found after rapid volume expansion in conscious dogs. Urine flow and sodium excretion were elevated (p less than 0.01) by 0.35 +/- 0.06 ml/min and by 65 +/- 12 mueq/min, respectively. Renal blood flow velocity was reduced (p less than 0.05) by 4.4 +/- 1.5 cm/sec. Neither right atrial pressure, left ventricular end-diastolic pressure, mean arterial pressure, the first derivative of left ventricular pressure over time (dP/dt), nor heart rate were influenced by the elevated ANF plasma levels. Circulating levels of vasopressin and aldosterone were unaltered by these increases in plasma ANF. Thirty minutes into the recovery period, all variables were similar to the preinfusion baseline. Thus, in conscious dogs, physiologically relevant increases in plasma levels of ANF reached diuretic and natriuretic thresholds.(ABSTRACT TRUNCATED AT 250 WORDS)