We examined the relative genetic and environmental influences on the variability in plasma
epinephrine,
norepinephrine, and
dopamine levels in 109 twin pairs.
Epinephrine levels were lower in females (P = 0.048). The
norepinephrine concentration increased with age (r = 0.40; P < 0.001). Blood pressure (BP) was not associated with
epinephrine levels in either sex or with
norepinephrine levels in females. In males, there was a positive association between
norepinephrine concentration and diastolic BP (r = 0.31; P = 0.020). A negative association between
dopamine levels and systolic and diastolic BP in females (r = -0.22; P = 0.014 and r = -0.20; P = 0.027, respectively) was not maintained after accounting for age, body mass index, and sex. Using path analysis and maximum likelihood model fitting, genetic, unique environment, and age effects contributed 57% (P < or = 0.001), 27% (P < or = 0.001), and 16% (P < or = 0.001) to the variability in
norepinephrine, respectively. Genetic effects explained 64% (P < 0.1) and 74% (P < 0.1) of the variability in
epinephrine concentrations in females and males, respectively. Unique environmental influences explained the remainder. Genetic and unique environmental effects explained 72% (P < 0.01) and 28% (P < or = 0.001) of the variability in
dopamine levels. These results indicate a substantial genetic influence on plasma
catecholamine levels. Although consistent associations between plasma
catecholamines and BP were not evident in this study, the observed genetic influence on circulating
catecholamines may be relevant to the potential role of the sympathetic nervous system in the early stages of
essential hypertension.