PLASMA DOPAMINE-β-HYDROXYLASE ACTIVITY AND BLOOD PRESSURE VARIABILITY IN HYPERTENSIVE MAN

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Abstract
Measurements of plasma dopamine-.beta.-hydroxylase (DBH) may allow for assessment of adrenergic tone and may elucidate a possible neurogenic contribution to essential hypertension. A series of measurements of DBH were performed in 57 normotensive and 50 hypertensive black and white men to compare DBH to selected blood pressure patterns and to evaluate the influence of salt intake, posture and race on plasma DBH. Plasma DBH, measured on unrestricted salt intake with subjects supine, was 42 .+-. 4 U[units]/l in white normotensives, greater (P < 0.05) than black normotensives (26 .+-. 6 U/l). White hypertensives had greater plasma concentrations of DBH than black (35 .+-. 3 vs. 24 .+-. 5, P < 0.05). Normotensives did not differ from hypertensives. Dietary salt restriction and upright ambulation increased plasma DBH activity in hypertensives. Although DBH did not correlate directly with blood pressure, high DBH values were associated with lability of blood pressure in hypertensives but not in normotensives. Multiple factors may influence plasma DBH activity and plasma levels may reflect more than adrenergic function. Essential hypertension may be a multifactorial disease and excess sympathetic neuronal activity alone is not sufficient to produce sustained hypertension.