Plasma epinephrine levels in hypertension and across gender and ethnicity

Epinephrine (E) infusions raise blood pressure and there is an excess incid ence of hypertension among males and blacks. However, reports off levels by ethnicity, gender, and blood pressure status are inconsistent. Insensitive assays, variability in plasma E levels within individuals, and the small s ize of most studies have contributed to these conflicting reports. We measu red plasma E levels in a large diverse sample of subjects, using a highly s ensitive assay. A total of 361 individuals participated in the study: 61% w ere men and 39% women, 74% were normotensive and 26% hypertensive, 59% were white and 41% were black. Except for difference in blood pressure and body mass index, between the normotensives and hypertensives, subjects had simi lar baseline characteristics and took no antihypertensive medications for a t least five days prior to sampling. All blood samples were collected after resting for a least 30 minutes following the insertion of an indwelling IV catheter. Catecholamine levels were determined using a radioenzymatic assa y (assay sensitivities for E and norepinephrine were 6 pg/ml and 10pg/ml, r espectively). An ethnicity by gender interaction was found (F-1,F-315 = 5.1 26, p =.024). Subsequent analysis revealed that white women had significant ly lower basal plasma E levels than white men (p <0.001) and black women (p = 0.036). There were no significant differences in E levels between black men and women or between white men and black men. Uncorrected E levels were lower in normotensive than hypertensive subjects (p = .009) but this diffe rence was not significant when corrected for body mass index (BMI). Uncorre cted norepinephrine levels were higher in women than men (p = .03) but the difference was no longer significant when corrected for BMI. Plasma E level s were significantly lower among white women than men or black women. In co ntrast to prior studies, E levels were lower in hypertensives, but this may reflect obesity among hypertensives.