Blunting of atrial natriuretic factor response to volume expansion by benazepril in hypertensive patients.

To verify the hypothesis that the angiotensin converting enzyme (ACE) level may affect the metabolism of circulating atrial natriuretic factor (ANF), the acute and chronic effects of benazepril on plasma ANF levels were studied in hypertensive patients under basal conditions and in response to acute volume expansion. Ten essential hypertensives entered a double-blind crossover study, and were randomly allocated either to placebo or to 10 mg benazepril orally once a day for 2 days; after a placebo washout period of 2 days the groups were crossed over. On the second day of each crossover period, volume expansion was induced by infusing 1 litre saline in 30 min, and blood samples for ANF measurements were drawn at times -5, 0, 5, 15, 30, 35, 40, 50 and 60 min. Oral benazepril at 10 mg/day was then given to all patients for 4 weeks, and the volume expansion with saline was repeated. After the 2-day acute benazepril treatment, blood pressure fell from 166.1 +/- 3.6/105.1 +/- 0.9 to 140.1 +/- 4.6/85.6 +/- 2.1 mmHg (P less than 0.01 for both systolic and diastolic blood pressure), whereas ANF fell from 29.4 +/- 3.6 to 24.1 +/- 3.7 pg/ml (NS) after the acute benazepril treatment and to 17.7 +/- 3.6 pg/ml (P less than 0.01) after the chronic benazepril treatment. The volume expansion itself did not induce significant changes in mean arterial pressure, either during the placebo treatment or during the acute chronic benazepril treatment. The rise in ANF values in response to saline infusion during placebo was prompt, beginning at min 15 and reaching a maximum at min 40.(ABSTRACT TRUNCATED AT 250 WORDS)