Urinary norepinephrine and epinephrine excretion rates are heritable, but not associated with office and ambulatory blood pressure.

Genetic and environmental contributions to urinary excretion rates of norepinephrine (U(NE)V) and epinephrine (U(E)V) and their association with blood pressure (BP) were investigated in 91 African American (mean age, 17.3±2.6 years) and 101 European American (mean age, 18.7±3.4 years) mono- and di-zygotic twins. Genetic modeling was performed using Mx software. U(NE)V (1.9±1.3 µg h(-1)) and U(E)V (0.2±0.2 µg h(-1)) were highly correlated (r=0.81, P<0.001). Significant heritabilities for U(NE)V (0.68) and U(E)V (0.74) without ethnic and gender effects were observed. The genetic correlation between U(NE)V and U(E)V was 0.86. There was no clear pattern of correlations for U(NE)V and U(E)V with BP measures in European Americans, but African Americans showed some inverse correlations of moderate size. Measurements of U(NE)V and U(E)V provide a viable method for the study of sympathetic tone and are substantially heritable.