Atrial natriuretic factor release by angiotensin II in the conscious rat

Since it was previously reported that atrial natriuretic factor (ANF) may exert an inhibitory effect on renin release, the existence of an Angiotensin II (Ang II)-ANF feedback mechanism was investigated. Male rats were infused intraperitoneally for 7 days with either saline, a nonpressor dose of Ang II (200 ng/kg/min), or a pressor dose (800 ng/kg/min) of Ang II. Systolic blood pressure, plasma ANF, 24-hour urinary sodium excretion, urine volume, and water intake were measured. A significant increase in plasma ANF was observed in the group with a pressor response (blood pressure rose from 89.0 +/- 3.9 to 136.7 +/- 11.4 mm Hg; ANF rose from 36.8 +/- 4.9 to 92.7 +/- 17.7 pg/ml). There was no significant time effect on 24-hour sodium excretion, urine volume, and water intake in both Ang II-infused groups. In a second set of experiments, male rats were infused intravenously for 60 minutes with either saline, a nonpressor dose of Ang II (16 ng/kg/min), or a pressor dose (800 ng/kg/min) of Ang II. Left ventricular end-diastolic pressure, right atrial pressure, and mean arterial pressure were monitored. There was a significant increase in plasma ANF and left ventricular end-diastolic pressure only with the pressor dose (blood pressure rose from 85.0 +/- 6.1 to 140.0 +/- 5.5 mm Hg; ANF rose from 22.6 +/- 6.0 to 108.3 +/- 47.7 pg/ml; left ventricular end-diastolic pressure rose from 5.3 +/- 5.7 to 20.8 +/- 7.9 mm Hg). No significant modification of right atrial pressure was recorded.(ABSTRACT TRUNCATED AT 250 WORDS)