Effects of Long-Term Treatments with Captopril on Blood Pressure and Renin Activity in the Stroke-Prone Spontaneously Hypertensive Rats

Antihypertensive effects of captopril, an orally active converting enzyme inhibitor were examined in the young and adult stroke-prone SHR (SHRSP) rats. The treatment was initiated at 6–7 and 14–18 weeks of age, and was continued for 12 and 17 weeks, respectively. The dosage of captopril was changed stepwise 3–30 and 3–100 mg/kg, orally per day in the young and adult rats, respectively. The effects of hydralazine were also determined for comparison. Captopril had a chronic antihypertensive effect when given in doses of 30 mg/kg in the young and 100 mg/kg in the adult rats. Captopril had no significant effect on heart rate throughout the experiments, while hydralazine increased the heart rate. Treatment with captopril decreased the incidence of vascular disease in the young and the severity in the adult rats, respectively. A decrease in incidence of cerebral stroke in the adult SHRSP was also apparent. More than a ten fold increase in plasma renin activity and about a two fold increase in kidney renin activity were observed in both the young and adult SHRSP at the end of the treatments. The results demonstrate the efficacy of long-term treatment with captopril in the management of hypertensive disease in SHRSP rats.