Antihypertensive and angiotensin converting enzyme inhibitory activities of a novel dihydrobenzofuran analogue.

1. The biochemical and pharmacological profiles of the novel, orally active angiotensin converting enzyme (ACE) inhibitor, N-[N-[[4-(2, 3-dihydro-2-benzofuranyl)-1-(ethoxycarbonyl)]butyl]-(s)-alanyl]- (s)-proline (BRL 36378), have been compared with those of enalapril and captopril. 2. In the conscious sodium deficient spontaneously hypertensive rat, BRL 36378 and enalapril (0.3-10 mg/kg orally) produced comparable falls in blood pressure; at 3 mg/kg orally, captopril was less active than BRL 36378 and enalapril. 3. In the anaesthetised spontaneously hypertensive rat, enalapril was slightly more potent than BRL 36378 as an inhibitor of angiotensin I (AI) pressor responses whilst BRL 36378 was about twice as potent as captopril in this test (i.v. route used). BRL 36378 and enalapril were equipotent as potentiators of bradykinin depressor responses. 4. In the anaesthetised Wistar rat, the maximum inhibition of AI pressor responses by 0.1 microgram/kg i.v. BRL 36378 and captopril was achieved sooner than after the same dose of enalapril. The inhibitory effect of captopril subsided completely by 40-50 min but the maximum effects of BRL 36378 and enalapril persisted for at least 60 min. 5. In the conscious renal hypertensive cat, captopril was slightly more potent than BRL 36378 or enalapril as a blood pressure lowering agent, over 1-10 mg/kg orally. BRL 36378 was more potent than enalapril as an inhibitor of AI induced pressor responses in this model. Captopril possessed similar inhibitory activity to BRL 36378 although minor differences in time course were apparent.(ABSTRACT TRUNCATED AT 250 WORDS)