Studies of the antihypertensive effects of CL 242,817, a new angiotensin‐I converting enzyme inhibitor [S−(R*, s*)]‐1‐[(3‐acetylthio)‐3‐benzoyl‐2‐methyl propionyl‐L‐proline]

The antihypertensive activity of CL 242, 817 and captopril were evaluated in conscious, unrestrained aorta‐coarcted hypertensive rats (AHR); spontaneously hypertensive rats (SHR); and in the two‐kidney, one‐clip, Goldblatt renal hypertensive beagle (RH2 dog). In AHR, equimolar oral doses of CL 242,817 (5 mg/kg) and captopril (3 mg/kg) had rapid onsets of action and relatively long durations of action. CL 242,817 was significantly more potent and longer‐acting than captopril. In the SHR, CL 242,817 was effective in lowering blood pressure by oral, intravenous, or intraperitoneal routes of administration, although less effectively than in AHR. In RH2 dogs, pretreated with the diuretic quinethazone, CL 242,817 (20 mg/kg, p.o.) lowered blood pressure more effectively than an equimolar dose of captopril (12 mg/kg). In RH2 dogs sodium‐depleted by furosemide pretreatment and maintained on a salt‐free diet to raise plasma renin activity (PRA) levels, CL 242,817 (20 mg/kg, p.o) was more effective than an equimolar oral dose of captorpril (12 mg/kg) in lowering blood pressure. In RH2 dogs, repletion of body sodium (and reduction in PRA) by maintenance on a normal sodium diet for 14 days decreased the antihypertensive effect of CL 242,817 and abolished that of captopril. The data suggest that angiotensin converting enzyme inhibitors (ACEI) are more effective in models in which PRA is elevated and the hypertension appears to be renin‐dependent. The RH2 dog that is sodium‐depleted by furosemide and mainted on a sodium‐free diet appears to be a suitable model for evaluating the antihypertensive effects of ACEI.