Release of atrial natriuretic factor during infusion of isoproterenol and angiotensin II.

Release of atrial natriuretic factor (ANF) is related to atrial pressure and heart rate and may be influenced by beta-adrenergic stimulation and angiotensin II. Experiments in five closed-chest dogs showed lower plasma immunoreactive (ir) ANF during intravenous (iv) isoproterenol (0.2-0.3 micrograms.kg-1.min-1) and higher plasma ir-ANF during iv angiotensin II (0.2-0.3 micrograms.kg-1.min-1) than during blood volume expansion measured at equal mean right atrial pressure (RAP) and heart rate. This indicated that the agents may affect ANF release differently, possibly through their effects on left atrial pressure (LAP). In five open-chest dogs with right atrial pacing at 216 +/- 1 beats/min, blood volume was expanded until mean RAP was 9 mmHg. Mean LAP rose to 16.8 +/- 2.0 mmHg, and plasma ir-ANF rose from 57 +/- 6 to 219 +/- 39 pg/ml. At a constant mean RAP of 9 mmHg, iv isoproterenol infusion reduced mean LAP to 12.6 +/- 1.4 mmHg and reduced plasma ir-ANF by 115 +/- 31 to 105 +/- 13 pg/ml. During iv angiotensin II infusion at a mean RAP of 9 mmHg, mean LAP rose to 23.2 +/- 2.2 mmHg and plasma ir-ANF averaged 281 +/- 77 pg/ml. The correlation between plasma ir-ANF and LAP (r = 0.83) indicates that the different effects of isoproterenol and angiotensin II on ANF release can be accounted for by the effects on LAP.