Low dose of ACE-inhibitor enhances sodium excretion in volume expanded patients with borderline hypertension.

ABSTRACT

The purpose of the present study was to separately investigate the effects of two different dosages of captopril on pressor, vascular and humoral response to acute extracellular volume expansion in patients with borderline hypertension (BHT). Thirty-five patients were randomly allocated in two groups undergoing acute saline infusion (0.40 ml/min/kg for 45 min and 0.15 ml/min/kg for 75 min)before and after a 7-day period of treatment with either placebo or captopril at the dose of 12.5 (LD-CAP) or 50 mg (HD-CAP) twice a day. At baseline the effects of LD-CAP were limited to an increase in PRA and to a decrease in plasma aldosterone whereas HD-CAP decreased systolic and diastolic blood pressure (SBP, DBP), forearm vascular resistance (FVR) and increased venous distensibility (VV(30)) as well. After saline loading patients treated with HD-CAP showed an increase in SBP, DBP not observed in patients allocated to LD-CAP. Urinary sodium excretion in response to NaCl loading was selectively enhanced by LD-CAP (+25%) whereas HD-CAP did not (+6.3%). The present data suggest that low-doses of ACE-inhibitors acting through a selective blockade of RAA not associated with hemodynamic changes can enhance the natriuretic response to acute volume expansion in borderline hypertensives.