The renin-angiotensin system and blood pressure - Differences between blacks and whites

Although blacks have lower plasma renin activity compared to whites, the co rresponding differences in serum angiotensin converting enzyme (ACE) levels have not been well studied. Furthermore, few studies have examined the rel ationship of renin activity and ACE levels to blood pressure (BP) in blacks . We addressed these questions in a cross-sectional study conducted in 110 blacks and 183 whites who were not on antihypertensive medications. Three B P readings were obtained during a clinic visit. Plasma renin activity was a ssayed by radioimmunoassay and serum ACE levels were measured by spectropho tometry. Mean systolic and diastolic BP were 122.6 and 77.9 mm Hg in the bl acks, and 123.4 and 77.9 mm Hg in the whites, respectively. Plasma renin ac tivity was significantly lower in the blacks compared to the whites (0.92 v 1.26 ng/mL/h, respectively, P < .05), but ACE levels were similar in both groups (28.8 v 29.6 U/L, respectively). Renin activity was significantly an d inversely associated with systolic and diastolic BP in both the blacks an d the whites. ACE levels, however, were inversely associated with BP in the blacks but positively associated with BP in the whites (P = .02 for intera ction on diastolic BP), even after adjustment for age, gender, body mass in dex (BMI), alcohol consumption, and heart rate. The corresponding interacti on between ACE level and race on systolic BP was of borderline significance (P = .06). These results suggest that levels of ACE are similar in blacks and whiles but their association with BP is possibly reflecting underlying ethnic differences in regulation of BP. (C) 1999 American Journal of Hypert ension, Ltd.