Ramipril prevents the detrimental sequels of chronic NO synthase inhibition in rats: hypertension, cardiac hypertrophy and renal insufficiency.

Inhibition of the angiotensin converting enzyme (ACE) with ramipril was studied in male Wistar rats during long-term inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME). Chronic treatment with L-NAME in a dose of 25 mg/kg per day over 6 weeks caused myocardial hypertrophy and a significant increase in systolic blood pressure (245 +/- 16 mmHg) as compared to controls (155 +/- 4 mmHg). Animals receiving simultaneously L-NAME and ramipril were protected against blood pressure increase and partially against myocardial hypertrophy. L-NAME caused a significant reduction in glomerular filtration rate (GFR: 2.56 +/- 0.73 ml.kg-1.min-1) and renal plasma flow (RPF: 6.93 +/- 1.70 ml.kg-1.min-1) as compared to control (GFR: 7.29 +/- 0.69, RPF: 21.36 +/- 2.33 ml.kg-1.min-1). Addition of ramipril prevented L-NAME-induced reduction in GFR and renal plasma flow. L-NAME produced an elevation in urinary protein excretion and serum creatinine and a decrease in potassium excretion which was antagonised by ramipril. L-NAME-induced increase in plasma renin activity (PRA) was further elevated with ramipril treatment. Isolated hearts from rats treated with L-NAME showed increased post-ischaemic reperfusion injuries. Compared to controls duration of ventricular fibrillation was increased and coronary flow reduced. During ischemia the cytosolic enzymes lactate dehydrogenase and creatine kinase, as well as lactate in the venous effluent were increased. Myocardial tissue values of glycogen, ATP, and creatine phosphate were decreased, whereas lactate was increased.(ABSTRACT TRUNCATED AT 250 WORDS)