Some haemodynamic and biochemical effects of captopril, metoprolol and their combination: low-dose regimen

ABSTRACT

In this study, renal hypertension was experimentally induced in male Sprague Dowely rats by applying a silver clip on the left renal artery. Low doses of captopril and /or metoprolol were intravenously injected to study their effects on blood pressure [B.P.] and heart rate [H.R.], or orally administered for 15 days for biochemical studies. Captopril [1.4 mg/kg i.v.] produced significant drop in B.P. with no change in H.R. while metoprolol [1.4 mg/kg i.v.] produced also marked drop in B.P. but with significant lowering in H.R. Their combination [1 and 2 mg/kg, respectively, i.v.] produced initially more lowering in B.P. which decreased later on, and significant lowering in H.R. After subchronic oral administration [5 mg/kg/day for 15 days], captopril produced a significant and marked decrease in angiotensin converting enzyme [ACE] activity, and a significant increase in plasma renin activity [PRA], but no significant change in plasma aldosterone [ALD] concentration. Metoprolol [5 mg/kg/day orally for 15 days] concentration. Captopril combined with metoprolol [each 2.5 mg/kg/day for 15 days orally] produced significant decreases in both serum ACE and plasma ALD. These results showed that with the small doses used, these drugs produced the usual hemodynamic effects, but somewhat different effects on the components of the renin- angiotensin-aldosterone system. Results were discussed in view of the effects of one drug on the hemodynamic response to the other drug