A comparison of inhibition of angiotensin I conversion by three converting enzyme inhibitors in rats.

1. The pressor responses to angiotensin I (AI) were suppressed in a dose related manner by the three converting enzyme inhibitors (CEI); SA 446, SQ 14 225 and MK 421. 2. The inhibitory action of SA 446 and SQ 14 225 was rapid in onset and decayed with time, while that of MK 421 was slower in onset and maintained for the 1 h of observation. 3. A single oral administration of MK 421 (80 mumol/kg) significantly decreased the pressor effect of AI 24 h later. In contrast, neither SA 446 nor SQ 14 225 reduced the AI-induced response at this time. 4. In anaesthetized genetically hypertensive rats, the depressor effect of MK 421 was greater than that of either SA 446 or SQ 14 225.