Increased Ratio between Changes in Blood Pressure and Plasma Norepinephrine in Essential Hypertension*

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Abstract
The pathogenic role of the sympathetic system in essential hypertension was evaluated by combined analysis of plasma catecholamine levels and the pressor sensitivity to endogenous norepinephrine [NE]. The latter was estimated indirectly by the ratio between changes in blood pressure and those in plasma NE after adrenergic neuronal blockage with debrisoquine (given orally for 6 wk). Normal subjects and patients with borderline or established essential hypertension had comparable pretreatment levels of plasma NE and epinephrine. Debrisoquine lowered plasma NE by a similar degree (almost 50%) in these 3 groups; blood pressure decreased only slightly in normal or borderline hypertensive subjects [-3.4 .+-. 3.2% and -5.4 .+-. 1.6% (SE), respectively] but fell significantly more (P < 0.005) in patients with established essential hypertension (-20.7 .+-. 3.9%). The ratio between percentile changes in blood pressure and those in endogenous NE levels was comparable in normal and borderline hypertensive subjects (0.03 .+-. 0.08 and 0.17 .+-. 0.04, respectively), but increased (P < 0.001) in established essential hypertension (0.62 .+-. 0.11). Essential hypertension may be maintained, at least partly, by the inappropriate association of normal plasma NE levels with increased NE pressor sensitivity.