CHARACTERIZATION OF ANGIOTENSIN-(1-7) IN THE URINE OF NORMAL AND ESSENTIAL HYPERTENSIVE SUBJECTS

A total of 31 healthy volunteers [39 +/- 7 (SD) years] and 18 untreate d essential hypertensive subjects [43 +/- 9 years] collected urine for 24 h after a physical examination and laboratory tests. Radioimmunoas say measurements of angiotensin-(1-7) [Ang-(1-7)] in urine and plasma were done as described previously. Sitting systolic and diastolic bloo d pressures (+/- SD) averaged 118 +/- 11/74 +/- 7 mm Hg and 146 +/- 16 /96 +/- 8 mm Hg in normal and essential hypertensive subjects, respect ively (P < .001), whereas 24 h urinary volume was not different in nor mal and essential hypertensive subjects (P > .05). The concentration o f Ang-(1-7) in the urine of normal subjects averaged 62.6 +/- 22.6 pmo l/L corresponding to a urinary excretion rate of 98.9 +/- 44.7 pmol/24 h. Concurrent measurements of plasma Ang-(17) showed that the content of Ang-(1-7) in urine was 2.5-fold higher than that measured in the p lasma. In contrast, untreated essential hypertensive subjects had lowe r concentrations and 24 h urinary excretion rates of Ang-(1-7) averagi ng 39.4 +/- 18.0 pmol/L and 60.2 +/- 14.6 pmol/24 h, respectively, (P < .001). Differences in the excretory rate of Ang-(1-7) between normal volunteers and essential hypertensive subjects were not modified by n ormalization of the data by urinary creatinine excretion rates. Urinar y concentrations of Ang-(1-7) correlated inversely with systolic, dias tolic and mean arterial pressures (r = -0.48, P < .001). Both urinary Ang-(1-7 [odds ratio of 0.92 (95% CI: 0.88-0.97)] and age were indepen dent predictors of systolic blood pressure. These studies demonstrated the presence of Ang-(1-7) in urine and the existence of reduced level s of the heptapeptide in individuals with untreated essential hyperten sion. The relatively higher concentrations of Ang-(1-7) in urine compa red to plasma agrees with data that showed that Ang-(1-7) may contribu te to the regulation of blood pressure. The inverse association betwee n Ang-(1-7) and arterial pressure provides a potential marker for the characterization of forms of essential hypertension associated with re duced production or activity of vasodilator hormones. (C) 1998 America n Journal of Hypertension, Ltd.