Effect of Propranolol and Indomethacin on the Depressor Action of Captopril in Patients with Essential Hypertension

The contribution of the renin-angiotensin system (RA) and of prostaglandins (PG) to the acute depressor effect of captopril (Capt) was studied in 13 hypertensive patients suppressing either RA by propranolol (Prop) or PG by indomethacin (Indo). Four patients showed abolition of the depressor effect of Capt by pretreatment with both Prop and Indo (Group 1). Indo, but not Prop, cancelled the depressor effect in another 4 patients (Group 2). In the remaining 5 patients, either Prop or Indo did not alter the depressor response to Capt (Group 3). Patients in Group 3 were older than patients in Group 1 and 2 and showed lower plasma volume value. Several mechanisms might contribute to the acute depressor effect of Cap, including not only the suppression of RA and the enhancement of PG, but perhaps other undetermined factor(s), especially in older patients.