An understanding of aminopeptidase A in hypertension is important, given its ability to cleave the N-terminal aspartic acid of potent vasoconstrictor angiotensin II. However, the role of aminopeptidase A in hypertension has received limited attention. Because we have succeeded in producing recombinant human aminopeptidase A, the effect of aminopeptidase A on systolic blood pressure in the spontaneously hypertensive rat was examined. Aminopeptidase A of 0.016 mg/kg was administrated intravenously to spontaneously hypertensive rats and blood pressure was monitored for 72 h. For repeated administration, aminopeptidase A doses of 0.016 mg/kg and 0.1-mg/kg doses of candesartan (an angiotensin II receptor 1 subtype blocker) were administrated daily in spontaneously hypertensive rats and blood pressure was monitored for 5 d. Bolus intravenous injection of aminopeptidase A at a dose of 0.016 mg/kg significantly decreased systolic blood pressure for 36 h in spontaneously hypertensive rats. A comparison of the antihypertensive effects of aminopeptidase A versus candesartan in spontaneously hypertensive rats showed that the effective dose of aminopeptidase A was about one-tenth that of candesartan. These results suggest the novel approach of utilizing aminopeptidase A to treat hypertension by degrading circulating angiotensin II before it binds to the receptor 1 subtype.

1 Methyldopa has a short plasma half‐life, but longer duration of antihypertensive effect. A single bedtime dose of methyldopa has been recommended to improve compliance and decrease side effects. 2 This double‐blind crossover study was designed to determine the duration of antihypertensive effect of methyldopa by comparing hourly supine and standing blood pressures, throughout the day during placebo, single morning dose, and single evening dose methyldopa therapy in 10 patients. The major side effects, drowsiness and dry mouth were assessed by visual analogue scale. Exercise blood pressures were measured 6, 12, 18 and 24 h after the dose. 3 The antihypertensive effect of methyldopa peaked after 6‐9 h and declined thereafter with a half‐life of approximately 10 h. Little antihypertensive effect remained 24‐26 h after the dose. The time course of the reduction in blood pressure during exercise and of the major side effects paralleled the antihypertensive effects. 4 The results suggest that the duration of antihypertensive effect of methyldopa is long enough to permit twice daily dosing, but that single daily dosing cannot be recommended for most patients. The study illustrates the importance of knowing the time of the last methyldopa dose when assessing blood pressure measurements in patients taking the drug.

No abstract