Plasma atrial natriuretic peptide in essential hypertension after angiotensin converting enzyme inhibition

The authors have already found that the antihypertensive action of β1-blockers is partially exerted through atrial natriuretic peptide (ANP). On the other hand, the antihypertensive action of angiotensin converting enzyme inhibitors (ACEI) seems to extend to other mechanisms. In this regard we studied the effect of the ACEI Cilazapril (C) on plasma ANP concentration in 21 patients, aged 40–64, with moderate degree essential hypertension. Assessments of the ANP and the other variables [(ECHO cardiac dimensions, blood pressure (BP)] were carried out before and after an 8-week treatment with 2–5 mg daily. ANP was purified by chromatography and assayed by radioimmunoassay (RIA). Systolic and diastolic BP decreased by 18% and 16%, respectively, left ventricular and left atrial diastolic diameters decreased by 6%. ANP increased by 5.7%. All changes were statistically significant. The discordant increase of ANP in relation to BP and cardiac dimensions suggests a direct effect of ACEI mediated either through the sympatholytic or the anti-carvoxypeptidase action. This effect may contribute to BP lowering.