Urinary Angiotensinogen Excretion Is Associated With Blood Pressure Independent of the Circulating Renin–Angiotensin System in a Group of African Ancestry

Although the circulating renin-angiotensin system (RAS) is suppressed in salt-sensitive populations, the role of the intrarenal RAS in blood pressure (BP) control in these groups independent of the circulating RAS is uncertain. We evaluated the relationship between 24-hour urinary angiotensinogen excretion and either office (mean of 5 measurements; n=425) or 24-hour ambulatory (n=340) BP independent of the circulating RAS in a community-based sample of African descent that had never received antihypertensive drug therapy. Circulating RAS activity was determined from plasma renin and angiotensinogen and serum aldosterone concentrations. Urinary angiotensinogen to creatinine ratio (angiotensinogen/creat) was correlated with plasma angiotensinogen concentrations (P<0.0005) but not with indexes of salt intake. However, urinary angiotensinogen/creat was independently associated with office systolic BP (partial r=0.16; P<0.001), whereas plasma angiotensinogen (partial r=0.07; P=0.14) was not independently associated with office systolic BP. Urinary angiotensinogen/creat was also associated with 24-hour systolic BP (partial r=0.11; P<0.05). The relationships between urinary angiotensinogen/creat and BP survived further adjustments for plasma angiotensinogen and serum aldosterone concentrations, plasma renin concentrations, estimated glomerular filtration rate, urinary Na(+)/K(+), or 24-hour urinary Na(+) excretion rates (P<0.005 for all). Participants with the highest compared with the lowest quartile of urinary angiotensinogen/creat showed an 8.2-mm Hg higher office (P<0.005) and 4.6-mm Hg higher 24-hour (P=0.01) systolic BP. In conclusion, independent of the systemic RAS, including plasma angiotensinogen concentrations, urinary angiotensinogen excretion is associated with BP in a salt-sensitive, low-renin group of African descent. These data lend further support for a role of the RAS in BP control in salt-sensitive groups of African ancestry.